Airco DH-2

[stephane.savard]

Whenever I've got the coroplast WWI biplane out at the field, there are always comments about how its amazing that its made of simple coroplast. Well, it really isn't all that hard nor too time consuming to build one of these things, and in the hopes that I might get some more interested (for WWI combat!), I'm going to post some pictures showing how it looks while being built.

At the end of last year I decided that my first coroplast biplane, the SE5a, was too heavy to serve as a combat plane, so I had started building the wings for the DH-2. Then winter came along and balsa building took over. This weekend I was still missing a piece for my Spitfire, so I turned to coroplast; first building a brand new wing for the damaged MiG-3 WWI combat plane, and once that was done, I turned to this project and decided to complete it. Since most coroplast projects are short, I can get back to the Spitfire once its done :)

For those that want to know, the DH-2 is my sixth coroplast project (of which one was abandoned as a bad job before ever reaching completion, and one making it to completion, but trashed since it never flew correctly)

http://stephane.savard.googlepages.com/DH-2_4Medium.jpg

Okay, so the problem with WWI coroplast planes is that there are NO plans available. None whatsoever. So you need to make do with a good 3-view and simple calculations. So first step is to go online and find a good three-view of the plane you'd like to build, and print it out as large as you can make it. I know I wanted to build at 1/8th scale, and I know the actual wing span of the real aircraft. So by measuring the wingspan on the 3-view, and comapring that to the 1/8th measurements of the real DH-2's wingspan, I then know that if I multiply ANY measurement on my 3-view by roughly 3.3 (your factor will vary of course), I will know what size to cut my coroplast! So as can be seen from the marked up 3-view, I came out with good 1/8th size dimensions for my entire plane. Only one word of warning here, not all 3-views are created equal. If possible, use all the measurements from one part of the 3-view, since I've seen the wingspan differ from the top-view to the front-view. If in doubt, TLAR works best. We're not entering scale combat championships :D

[stephane.savard]

http://stephane.savard.googlepages.com/DH-2_1Medium.jpg

So what to do with these measurements? Well, I draw up a rough 1:1 plan of the fuselage. This is just to help me visualize where everything will go. I know Eric takes it one step further and actually uses his computer for the drawings, but I decided to keep it simple, plus I like to work on this in my workshop, which happens to be away from the computer.

Obviously, from the pictures above, I've already started executing on my plans. Like I said earlier, the wings were completed last year and I don't have any pictures showing how they were built. It is in fact pretty much standard, and you can find an awful lot of websites that describe how to build a wing using 2mm coroplast and a yardstick. The only difference here is that I used contact cement to glue small rectangles of 1/8" ply in each wing. These are located at each point where the aluminium brackets are located (six in each wing - the top of the bottom wing, and the bottom of the top wing). There are also four more smaller ply pieces in the top wing center section for the cabane struts. We'll see those in greater detail when I get to building the struts.

[stephane.savard]

http://stephane.savard.googlepages.com/DH-2_2Medium.jpg

This is how the inside of the fuselage is made. All coroplast to wood joints are glued using contact cement, and most wood to wood joints are glued using polyurethane (one common brand is this type of glue is gorilla glue). For the formers, I used 1/8th aircraft ply, because I had a lot of it on hand. I am however starting to run out, and my next planes will use liteply (or, you can also use several layers of balsa, laminated cross-grain). I used two balsa blocks I had laying around to shape the nose. Heavier than foam, but with the engine behind the CG, I will need some weight up front, and something solid to deal with my now infamous landings. The landing gear block will be used for exactly that, holding the front of the landing gear.

http://stephane.savard.googlepages.com/DH-2_3Medium.jpg

Hind view of the fuselage, the firewall is showing and is made of typical ¼” ply because I had plenty on hand. That’s the nice thing about coroplast planes, you can build them with whatever you find in your workshop. I’ve even once experimented with cardboard, but turns out it’s not that great of a material for turtle decks :)

I’ll try to keep this thread updated with more pictures as I go along with this build, and hopefully it’ll get someone interested enough to build their own WWI combat plane!

Enjoy!

[Eric Marchand]

All right ! ever since I tried the DH-2 on the sim, I've been curious to see if an actual airframe would have the same weird flying characteristics. Can't wait to see it in the air !

What kind of spacing do you have between the rear wood struts for the propeller ? Enough for a 6" ?

[stephane.savard]

Hmm, I'm not quite sure what you're asking. If you look at the picture with the wing, you'll see that the trailing edge has a cut-out are in the wing center section. This is a rough indication of where the propellor will be located.

Actually, even better, take a look at the second picture above where I have the hand-drawn plans. If you follow the center line at the rear end of the fuselage, you'll see the location where I marked the drive washer for the engine. And on the same drawing, the dotted lines at the trailing edge of the wing shows where the "cut-out" appears.

Finally, I don't quite remember the exact details, but the cut-out is about 12-13" across, with the wood tail struts attach to the outer edges of this. There is more than enough place for the prop to clear all struts, but the problem will be trying to find a propellor and starting the engine!

See, last time I checked, there were very few sizes of pusher propellors available (i.e. very little in the 9x4 and 9x5 range.

As for the simulator, I have a feeling that the model is not accurate (I tried the same one), it just felt wrong. Something about being able to hover it was weird. But I could be wrong, we'll know soon enough! I already started working on the tail struts and tonight I should have more pictures showing this.

Later!


Edit: actually, about the spacing, what threw me off was the mention of 6", this plane will be just a little smaller than the SE5a, and I'm planning to put in a 9 or 10" propellor.

[Sunfly]

Nice work Stephane.
I don't want to be a pain .... but I am ... I can,t help it.
The fact the prop is a pusher and that it will be in the back I think will
make it difficult in combat to cut your opponent streamer, will it.
Good for the rest of us! :D:D

Not necessarily for this project but for future ones, as you may be committed to
a specific engine by now, here is an idea:
For pusher engines projects you can use a Saito 4 stroke and order the cam shaft for counter rotation.
So, the engine will run in the other direction.
Like this you would have all the choice of the standard propeller available.
This brings another question:What would be the displacement allowed for 4 stroke engines on combat planes.
Will it be 0.25 X 1.5= 0.375 meaning we would use a 40 size engine to be in the same power / advantage range ?

Is there documentation or written rules about combat plane and 4 strokers?

See you in those troubled skies.

Cheers,

[stephane.savard]

Honestly, I have no idea what is the allowed displacement for 4-strokes. The thing is, there are no official rules for WWI combat. They seem to change slightly at each contest held in Ontario. For example, WWI monoplanes used to be allowed if using a .15 engine, but that's no longer allowed. I would even be interested to know about electric motors. The best thing is to post on rccanada, in the combat forum, which incidentally, is where the "official" rules are currently found - buried in some of the posts.

Honestly though, we don't exactly have hard rules here at wimac concerning combat, they seem to be mostly guidelines more than anything :)

As for cutting the streamer, umm, well I never gave it much throught really, and I will be at a slight disadvantage. But, you should know that it is not necessary to cut the streamer with the prop; in WWII combat, I've cut streamers using only the wings. How will this work with a slower flying biplane? I have no idea, we'll see I guess. Those times when you see us hit a streamer and the whole streamer pulls off? That's usually a case of the wing hitting the streamer instead of the prop hitting the streamer.

Not that it matters much, since no-one except me has any WWI combat planes :D

But maybe it would be time for use to order combat-legal streamers. They are supposed to be 1" width, not the ~2" width we currently use.

[Sunfly]

When my Corospit will be ready I suggest I travel back in time to fight with
the WW1 guy((s)).
We can't leave you alone you will get bored too fast :D:D:D

[Safety First]

I like that boat with wings...:cool:

[stephane.savard]

Luc, I have a WWII combat plane combat ready as of last weekend (which just happens to be the plane with the most victories so far - just thought I'd mention that :D )

And yup, boat-with-wings is a good description of the tub :)

[stephane.savard]

http://stephane.savard.googlepages.com/DH-2_5Medium.jpg

Here's the back end of the DH-2. Hardwood dowels that were bought at Reno-Depot sometime last year. I initially used some carpenter's glue to hold it all together with the thought of using some screws afterwards. The whole structure was rather flimsy, so I glued the triangles on both sides of each joint with LOTS of epoxy.

Also seen is the template for the stabilizer; soon I will transfer this to coroplast. The plywood triangles might also serve another purpose in the end. After I permenantly glue on the stabilizer and make the rudder assembly, I'll see how rigid the structure is. If too frail, then I'll drill holes in the triangles and use that to thread light wire and secure the whole structure in much the same way as the real DH-2.

Now I need to figure out how to attach all of this to the wings! I have a good idea to glue the dowels against plywood plates that fit in the wing (this is what is already planned), but I'm having doubts. Anyway, this is half-improvised anyway, I'll see what happens next time I go down to the workshop :)

Enjoy!

[Sunfly]

Can you eat chinese food with this?
Sorry, I have to replace Albert during his absence.

[Eric Marchand]

I can set you up with VERY light nylon covered steel wire, if it come to that.

[stephane.savard]

Eric,

The epoxy had time to cure overnight and I don't think the wire will be necessary; the ply triangles really made the entire structure incredibly strong and resistant to torsion.

Plus, once the stab and fin are in place, and the other ends are embedded into the wing, I think I'll end up with a very strong structure. After the first flights, I'll see if I can add the wires anyway for looks; it will depend on the amount of drag I already get.

The SE5a has all the fittings installed to add scale flying wires, but in the end the power and weight meant that I left the wires off.

That tail will certainly be light, but I will still need to add weight to the nose. The engine is behind the CG; and with nothing else but the fuselage pod in front of the CG, there just isn't much chance of being nose-heavy on this one :) So far, both wings and the fuselage weighs in at exactly 2 pounds. Tonight I'll finish the tail, but the tail struts can't be more than a few oz.

[stephane.savard]

Turns out I found my propellors; wood Zinger pusher 9x4's should be perfect. Since I need to order them, I figured I would order myself a new battery pack and a new receiver at the same time for another little project. Eric; what is the Berg recveiver you use? the Berg 4 or the 4L? And how do you connect a battery if you use all 4 channels?

[Chris Bowes]

I have used both the 4 and 4L in my combat planes and have been impressed with both, the 4 is pretty much bullet proof being encased in resin, for the small cost increase I would recommend this. Not sure how you connect the battery if using four channels, i have a suspicion you can just put a y-harness on one of the connections but not sure, the foamie i used the 4L on has the battery connected to the ESC so all four channels are free for servo's.

[stephane.savard]

I think that's what Eric had said, to use a y harness, but I just want confirmation.

(I have six y-harnesses! from the defunct Bronco, that plane was a mess of wiring, ha!)

[Eric Marchand]

Y harness works great, for weight reduction and cleanliness I have also spliced power leads directly into a servo wire. Both do the job.

[stephane.savard]

Got around to building a bit more of the Airco late this afternoon.

http://stephane.savard.googlepages.com/DH-2_6Medium.jpg

The above image shows how I glued the the stabilizer to the wooden structure. I use Household Goop, something that can be found at canadian tire. It's silicone based I think. Great stuff, but very heavy, so use spareingly. Once dry (overnight), the only way to seperate the coroplast from the wood involves destroying it.

Also, I've installed a wire rod (2-56 sized wire) with an outer tube; this will be used for the rudder, more to come on that.

http://stephane.savard.googlepages.com/DH-2_7Medium.jpg

Here is the result seen from the top. Seen faintly through the coroplast is the wire I embedded in the elevators

http://stephane.savard.googlepages.com/DH-2_8Medium.jpg

A bit out of sync here, but I had started working on the struts to hold the wings together. I unfortunately realised that I only had two 6-32 x 3/8" bolts left, so after making these two struts I had to stop.

Basically, its just some dowels that are sanded slightly on one side at each end, a hole drilled through and that's it. My SE5a has had problems with broken struts (not helped by Chris flying his Spitfire's wing through them), so I will cover the ends with heat shrink tubing to making them stronger. Will also look rather cool!

More to come later this evening...

[stephane.savard]

http://stephane.savard.googlepages.com/DH-2_9Medium.jpg

Getting back to the tail end of the Airco, here's a good trick into making a solid fin. These are fairly thick bamboo skewers that can be bought at most supermarkets.

http://stephane.savard.googlepages.com/DH-2_10Medium.jpg

The above image shows what it looks like once the fin is glued (again, with household goop) onto the stabilizer. I had two types of bamboo sticks, one was way too small, and I had a single stick of the one I used - which happens to be a bit too big. The flutes of the fin actually bulge a bit. Once the coroplast is painted, a lot of this won't show up.

By the way, in my experience, until the coroplast is painted and finished up, a coroplast plane looks rather awful :)

http://stephane.savard.googlepages.com/DH-2_11Medium.jpg

And here's the rest of the rudder. There really isn't much of a fin on the Airco, making the traditional way of hinging coroplast rather useless. That's why I added a the tube over the wire. I glued to the edge of the rudder to the tube, making a great hinge. I will however add tie-wraps around the tube and embedded into the rudder as an extra precaution.

http://stephane.savard.googlepages.com/DH-2_12Medium.jpg

And as a final picture for today, a preview of sorts. I just lay down everything in their rough positions (some bottles of epoxy are proping up the top wing :) )

I'm looking forward to finishing this plane! So far the weight is looking good, the entire tail assembly is currently weighing in at 5.7 oz.

Later!

[stephane.savard]

It just occured to me; how do I setup a fuel tank's internal plumbing on a pusher prop plane?

[Safety First]

The same unless your flying backward...

[zorba]

thats a good one. ow do you come up with those things Andre?

[stephane.savard]

So the fuel pickup clunk goes to the back of the fuel tank, which is pointing at the nose of the airplane?

Or, the fuel pickup is at the back of the tank and the fuel tank's butt is pointing at the butt of the airplane, resulting is extra long fuel and pressure lines?

I don't get it :)

[Safety First]

On one of my os37 I have 12 in medium fuel line never had a problem.
Now the other question would you try to hover a plane with a reverse klunk clunk or klonk I don't remember how to spell it. Sorry tank pointing front. Also tiewrap on all your lines put a one a piece fuel filter on your pressure line. You must backwash the filter every 10 flight.Put a fueling line on your tank this way you don't have to remove your line from carb or muffler. Now your'e ready to fly an Heli.

[stephane.savard]

Ah, see, I had the opposite, I had a whole bunch of problems with a long fuel tube/pressure line in a combat plane. When I shortened it up, the problem dissapeared. But, who knows, I might have inadvertantly fixed another problem and the long fuel tubes were not the real cause.

[Eric Marchand]

I don't think the orientation of the clunk is a factor, as you accelerate as much as decelerate, in theory...

So I would say the clunk is at the back of the tank, pointing at the nose, and keep a slight incline so the clunk is always submerged.

Keep the fuel lines short, if at all possible.

[stephane.savard]

Moving on....


http://stephane.savard.googlepages.com/DH-2_13Medium.jpg

Here's the view of the new struts I added to the wings. Trying to get both wings at an exact incident is not easy, and even less when working with coroplast. But I did fairly well, with about 0.5cm difference. I encased the end of the struts (5/16 diameter) with heat shink tubing to prevent splitting that I was experiencing on the SE5a.

http://stephane.savard.googlepages.com/DH-2_14Medium.jpg

The above shows how I am planning to fit the tail onto the wings. When I built the wings, I had allowed enough space for these rectangular 1/8" thickness ply plates. These can then be slide into the wing, and a notch is cut to accept the dowels.

http://stephane.savard.googlepages.com/DH-2_15Medium.jpg

Here I attached a small jig to keep the plates at the correct angle while being glued to the dowels. The holes that I put into the plates (and the bolts) will later serve to anchor the plates onto the wing. I will also add an L-bracket and a interplane strut just like the ones seen in the first image above.

http://stephane.savard.googlepages.com/DH-2_16Medium.jpg

And here the joint is how I left it about 15 mins ago; soaking in epoxy. I will sand off some of that so that it fits into the wing. I think it's going to be a strong joint, actually, the weak point is probably the 1/4" dowels of the tail itself.

Unfortunately, that's it for tonight, I have to wait for the epoxy to cure, and tomorrow I will work on the bottom plates - I can only one wing at a time, because the angles are critical.

Later!

[stephane.savard]

http://stephane.savard.googlepages.com/DH-2_17Medium.jpg

Last night I epoxied the plates to the lower struts, and tonight, I finally fitted the tail to the wings. The above image shows the plates firmly inside the upper wing, and bolted down with 6-32 bolts and a plastic washer. The washer I made out of scrap plastic.

The lower wing is done exactly the same, but the washer sits on the bottom of the wing... next picture shows why.

http://stephane.savard.googlepages.com/DH-2_18Medium.jpg

On the insides (top of bottom wing and bottom of top wing :) ) I put in L-brackets and added the wood struts. The whole thing is very secure and as a non-scientific test I took the dh-2 by the wings and shook it all about. The tail does not move!

http://stephane.savard.googlepages.com/DH-2_19Medium.jpg

http://stephane.savard.googlepages.com/DH-2_20Medium.jpg

Here's an overall view of the DH-2 so far; the main structure is in place and now its the loooong process of fitting everything; cabane struts, landing gear, engine, servos, etc etc.

But, I've got a teeny problem; my only flying plane so far is the SE5a, which will also need to canabilized for parts to the DH-2. More on this later...

http://stephane.savard.googlepages.com/DH-2_21Medium.jpg

Final picture of the day is the tail wheel. Yes, I know, the DH-2 should have a simple skid. Actually, not so much a "skid" as just a piece of wood sticking out the back. I build difficult to fly planes yes, but I'm not silly enough to go and not put a tailwheel; flying a WWI biplane in our cross-wind cursed field without a tailwheel wouldn't be much fun :D

This is just a piece of wire that I bent into shape. I put a small "V" in the wire and using two control horn nylon plates, I sandwich the "V" between the plates. I also added the tie-wraps to further secure the rudder to the tube.

Okay, so what about theequipment for this bird? Initially I was going to use the SE5a's engine and most electronics. Then I crashed the MiG and thought I'd use those. Well, yesterday, as I took the engine and fuel tank out the stricken MiG, I decided to give a try at repairing it. I flooded the nose and firewall with both goop and polyurethane and I think I may have actually done the job! I still need to figure out the problem with the wing; but I will wait before taking apart the SE5a. If the MiG flies, then it's a go, else - well I don't want to be stuck with nothing to fly if the Dh-2 doesn't work out.

Anyway, as always, enjoy!

[stephane.savard]

I forgot to mention, as seen in the pictures above, the current weight stands at 2 pounds, 10 oz.

[stephane.savard]

http://stephane.savard.googlepages.com/DH-2_22Medium.jpg

I worked on the main landing gear these past few days. It's made of 5/32 wire, and the thing in the picture above is the wire bender by K&S. It's a great little and uncomplicated tool; fit it in a vice and bend away!

http://stephane.savard.googlepages.com/DH-2_23Medium.jpg

The above shows the result of the second set of gear I attempted. The first was all ready and on the plane when I realised that one leg was longer than the other. Ah well, I built this second one to fix the problem. The thing is, that while bending wire is very easy with the wire bender, finding the correct angle at which to bend is much harder.

http://stephane.savard.googlepages.com/DH-2_24Medium.jpg

The axle is simply a second piece of 5/32 wire. The joints are wrapped tightly in copper wire and then silver soldered into place.

http://stephane.savard.googlepages.com/DH-2_25Medium.jpg

And the gear now is soldered and put into place on the plane. The back ends of the wire gear are simply bend up and fixed into the wing. A later picture will show how that works. The gear fits inside a goove in the wood (landing gear block), and a couple straps hold it down. This is pretty much the same as on the SE5a. Oh by the way, there is a plywood plate embedded in the wing that was put into place when I first built the wing. It's purpose is exactly as seen here; holding the landing gear and the wing bolts.


...

[stephane.savard]

http://stephane.savard.googlepages.com/DH-2_26Medium.jpg

These are the wheels and how to "fix" them. They were bought at walmart - they come from a 15$ baby stroller. 15$ for eight wheels is damn good! Since using these same wheels on the SE5a, quite a few people have commented to me that they must be rather heavy. This is far from true, in fact, each weighs 1.3 oz! They are all plastic, and the black "tire" is something of a cross between vinyl and err, rubber. Though calling it rubber is really a stretch :D

The holes in the wheels are much too big for the axles, so the best bet is to slip in a 1/4" dowel (fits tightly) and a drop or so of CA. Then use a drill press to drill out a 5/32 hole for the axle.

http://stephane.savard.googlepages.com/DH-2_27Medium.jpg

Here's where the wire gear sticks through the wing; I just use wheel collars to hold it in place. Oh, and the dotted line on the firewall will be the centerline for the crankshaft. Technically, on the real Airco DH-2, the entire center section of the bottom wing does not exist (search google for DH-2 pictures to understand this), but I've decided to keep it simple here - a one piece wing.

http://stephane.savard.googlepages.com/DH-2_28Medium.jpg

Couldn't resist taking a picture of the whole thing now that it stands on its own legs! In this picture, the entire airframe currently weighs 3 lbs 2 oz; and it balances on the rear interplane struts! This is great news, it means that the engine sits very close to the current balance point, and I will not need too much weight up in the nacelle's nose to bring the balance point closer to the actual spar.

http://stephane.savard.googlepages.com/DH-2_29Medium.jpg

I took a picture of the whole landing gear assembly since I took the nacelle off the wings. Shows how the back of the struts are bent up.

I took the nacelle off because its now time to fit the engine, fuel tank and servos. I might be flight ready this weekend! No more picture for tonight, I took the rest of the evening disassembling the SE5a for the engine, receiver and battery pack and mini servos.

Enjoy!

[stephane.savard]

Also forgot to mention; the wheel base is not too far off being scale. I moved the wheels slightly forward opf the leading edge and made the stand a bit wider. Should make landing and takeoff much easier to handle than with the SE5a.

[Eric Marchand]

That thing looks sooo cool ! Let me know if you go and fly it this week end, I want to be there for the maiden flight !

Oh and by the way, nice job on the soldering !

[Sunfly]

It looks very pretty Stephane.
I look at the real size airframe pictures and your model ,once painted, will be looking like the real ones.

That's a work of passion and patience.

Congratulations!

[stephane.savard]

Thanks guys!

I'm getting better with the solder for sure. I puts lots and lots of flux, and then keep adding heat and silver solder until it's literally dripping :D Someday I'll graduate to no-drip soldering.

[stephane.savard]

The Airco may not be ready this weekend; I ran into some problems. Sorry, no pictures yet. First problem was getting the interplane struts connected - there's not a whole lot of place in that small fuselage. Which leads me to the second problem...

Actually, lets just say that electrics are becoming increasingly tempting by the simple fact that they don't need a servo and pushrod to actuate the bloody throttle arm. This simple little detail has given me problems in every single plane I've ever built.

Maybe pictures tonight.

[Safety First]

It's a pleasure to watch this old coucou coming to life. Very nice!

[stephane.savard]

The DH-2 is one of my favorite WWI planes, and old coucou is good description :)

one to tonights pictures then...

http://stephane.savard.googlepages.com/DH-2_30Medium.jpg

I hinted at problems, and some were easier to fix than others. This here was a realtively simple one. I got ahead of myself and had not added a hole to allow the fuel tank to fit inside the fuselage. I used my dremel to carve out a suitable hole.

http://stephane.savard.googlepages.com/DH-2_31Medium.jpg

Here was another problem, a somewhat more difficult. Prior to adding these 1/8" wire cabane struts, the only thing holding the nacelle to the bottom wing was the wing bolts. That made the thing rather unstable, especially when there will be at 9x4 prop spinnign at 15000 pushing on its behind. The cabane struts simply poke through the coroplast and are bolted to the side bulkheads in the fuselage. I used nylon landing gear straps for this. Unfortunately, that means we have bolts showing through the sides. Once painted the bolts will barely show.


http://stephane.savard.googlepages.com/DH-2_32Medium.jpg

http://stephane.savard.googlepages.com/DH-2_33Medium.jpg

Here's how it looks once put into place. The cabane struts are fixed to the upper wing with more nylon landing gear straps. (you know, WWI coroplast biplanes use up a heck of a lot of hardware!)

The prop has roughly 1/2" of clearance in back of the wings, and if it turns out to be too little, I can increase that by another 1/4" I think. Also, notice why I had to put a funky bend in one set of cabane struts - to clear the muffler!

Oh, and here's a perk. Everyone knows how great my landings are; well, from now on, the engine will stay running no matter what attitude the plane ends up in, even if it's laying on it's top! :D

http://stephane.savard.googlepages.com/DH-2_34Medium.jpg

Here's where I put the throttle servo. Originally the servo is supposed to be inside the plane, but this ended up being just about the only way to connect it. Stoopid throttle pushrods.

(and yes, the muffler's extension will have to point somewhere else, it's still in the same configuration as I had it on the SE5a).

http://stephane.savard.googlepages.com/DH-2_35Medium.jpg

Final picture for today is just to show how the aileron servos are being installed. Cut a hole in the wing, add wood blocks, and there you go, it's done.

That's it for today. Actually, I did three things after that last picture. 1) I dissabled the fuselage. 2) I took some black fuel proof spray paint (tremclad) and painted the firewall, inside the "fuel tank compartment" and the cockpit area, and 3) I mixed a batch of finishing epoxy and "painted" the balsa nose to make it stronger. Since I did not takle too much care in aiming the spray can, it currently looks like crap; but once the next colors go on it will look great :)


Here's something for you guys; how should I connect the elevator and rudder? :) The servos will be in the wing, exactly in the same manner as the aileron servos, except of course they will be very close to where the tail struts meet the wing. I have several choices in how to actually make the connection. Any ideas? I haven't yet made a choice!

My current thinking says to simply zip-tie some sullivan gold-n-rods to the tail struts. Once painted it shouldn't look to bad. I'm open to suggestions, heh!

[stephane.savard]

Oh again, I forgot. I did not weigh the plane when it had the engine on, but I stuck the receiver and the battery pack inside the cockpit area and "balanced" the plane for the heck of it. It currently balances pretty much in the center of the wing! Things are looking good to have a relatively light plane!

The amount of effort though rather defeats the purpose of combat. A WWII plane can be done in a week, but this; well, like the SE5a, it's the equivalent of a month! (and to think some of you take this much time assembling an ARF, ha!)

[stephane.savard]

Update again.. it's not clear above, but the aileron servos are being added to the bottom of the top wing. The rudder and elevator servos will be located also on the top wing. That's because the stabilizer is attached to the top tail struts; easier to connect the pushrods. I have plenty of servo extensions to route the servo leads out of the top wing, down the cabane struts into the fuselage. I may use Y cables to reduce the number of wires.

[Sunfly]

Hi Stephane,
Looks good !
By examining the last photos you posted I have the firm impression you should flip the propeller the other way. It will still be a pusher prop but will be a lot more efficient.
I can't help it I often see snags. ( even in my own things )
So, do yourself a favor, flip this prop. ( for me) .:D


Cheers

[beto9]

Que pasa con el Spitfire?

[stephane.savard]

Ha, you're right, I just took a look at the photos and yes, I put on the propellor backwards. Or rather, the propellor used to be on backwards (I've since taken it off - but had you not told me, I would of put it back on the same old way)

I guess it was just automatic, I assumed the "ink" pointed away from the engine, just like when the engine is facing the other way.

Albert; I have one more project to work on before getting back to the Spitfire :)

[stephane.savard]

Only two pictures tonight!

http://stephane.savard.googlepages.com/DH-2_36Medium.jpg

http://stephane.savard.googlepages.com/DH-2_37Medium.jpg

This is pretty much what I worked on this evening. As mentioned yesterday, I tie-wrapped some gold-n-rods into place. Since I'll be painting the tail structure gray, it should pass as acceptable.

So what's left? Well, here's my unofficial todo list:

1. add the control horns and pushrods to the ailerons
2. connect the upper and lower ailerons together
3. add a bottom/floor to the fuselage
4. add the switch harness and the fuel dot.
5. find someplace to put the receiver, and re-assemble the plane as ready-to-fly. This will include cutting the holes to route the servo leads from the wing to the fuselage (or vice-versa if the receiver ends up being in the wing)
6. rejoice and take a few pictures for you guys.
7. dissamble the whole lot
8. paint.
9. apply decals.
10. reassemble
11. fuel up and maiden.


Og I almost forgot, I did paint the fuselage in gray today, but somehow the paint bubbled (it was an older paint can), I had to wipe it up and start over. The paint job looks awful, so I'll wet sand it smooth before re-applying paint.

Technically, I might be able to finish tomorrow, but it's probably not going to happen. It will definately be ready sometime this week though!

[stephane.savard]

http://stephane.savard.googlepages.com/DH-2_38Medium.jpg

The Airco is now painted! I did some of the last painting this morning, and it's now drying. By the end of the day I will begin re-assembling this plane and making the decals.

I used Tremclad spray paint; its available in quite a few colors, and is perfectly fuel proof. At least the standard colors are. I have not tried their "aluminium" color yet; and of course stay away from the rough texture paint (why you would want a rough textured paint job on a plane is questionable).

The problem though is that being spray cans, it is very difficult to control. Some colors are also a lot harder to apply than others. The flat colors (i.e. the brown in this picture) are the very best and I wish they made ALL their paints flat. The gloss are a mixed bag, with Gray being one I dislike. It sometimes goes on very thin and runny, and other times thick and splattering. Actually, most of the gloss colros are hell.

So far, I have not yet found another commercial paint that is fuel proof. Yes, I know about automative two part paints, but I am not touching stuff that you should be painting with a hazmat suit. Do not necessary trust ANY internet post (including this one :) ) that mentions that brand XYZ of paint is fuel proof. Do your own tests. Chris and I both found out that internet posts can't be trusted. Oh and if the integredients on two brands of paint cans are the same - don't think that they are both fuel proof. I learned that one the hard way. And one last bit; letting the paint cure for a week, and then swabbing the paint with raw fuel is not a good test either. It might survive that, only to gradually turn gooey as time passes. Thankfully, that lesson was learned at the same time as with the ingredients, and only one plane suffered, ha!

Later!


Lots of hardware huh? :)

[Ronald Longtin]

Voici une référence pour des peintures à l'eau conçues spécialement pour les maquettes.

http://www.nelsonhobby.com/paint.html

[zorba]

you can also go to Car Quest on Gouin west and the the paints in the amount you want. They are made by BASF Limco and R/M. Thats where I got the paint for my projects. They can put them in a spray can for you if you want.

Cheers

[stephane.savard]

Nelson's sounds good, but pricey for coroplast planes; but I'll keep them in mind for my Spitfire though!

No pictures for today, I didn't quite finish the DH-2 last evening. Most of the decals are on, and the only things left is to find a pilot, make a gun, and add the red, white and blue to the tail.

I also need a bit more lead for the nose, turns out that it was a bit trickier to balance than expected because of the heavy tremclad paint. Total weight will be 5.6 lbs. :)

[Eric Marchand]

Still a featherweight compared to the Se5-a ! Good work my friend !

[stephane.savard]

Here we are! This are the final pictures until I get to the field to take proper pictures of it on the runway. Only a few things left to do before flight...

http://stephane.savard.googlepages.com/DH-2_39Medium.jpg

http://stephane.savard.googlepages.com/DH-2_40Medium.jpg

http://stephane.savard.googlepages.com/DH-2_41Medium.jpg

http://stephane.savard.googlepages.com/DH-2_42Medium.jpg

http://stephane.savard.googlepages.com/DH-2_43Medium.jpg

Actually, nitpickers might notice that I don't yet have the upper and lower ailerons connected together. I need two pushrods for this, and I currently don't have any left.

I also need to setup the radio - throws and exponential, etc. All the controls currently move in their correct directions and without binding, but I'm pretty sure (based on the SE5a) that it needs some fine tuning.

I also need to properly balance the plane. I don't have enough lead, and will pick some up at the same time as the pushrods this thursday. Currently, I have about 5 oz of weight up front. I estimate that I'll need an additional 2-4 oz, and the battery cannot go any more forward without strapping it to the nose. That engine behind the CG does end up making the CG difficult to fix. Current weight is 5 lbs 10 oz. Even with more 6 oz (worse case) additional nose weight, it will still be more than a full pound lighter than the SE5a.

I do have a bit of a umm, problem. Anyone here would know how and be willing to build me a cord with remote glow plug??? It never dawned on me that the upper wing would block access for my glow starter! :o

[stephane.savard]

I just calculated the wing loading; if I do end up adding 4 oz additional nose weight, the current wing loading would be 22.12 oz/sq.ft

[Eric Marchand]

Well, you can just buy a remote ignitor hookup, like they use a lot on helis, I've used them a lot on in-cowl engines, I'll look and see if I have a spare, or, you could just use aligator clips wired to a rechargeable C or D cell. Let me know if you need help with that, I'll look into my spare parts for that remote hookup.

[Eric Marchand]

Oh and by the way, I'm extremely jealous of that plane...I think I might make my WWI fighter my next project after I finish my Extra.

Great job !!!

[Chris Bowes]

Very nice job Stephane, what a difference a paint job makes! How about flipping that prop? the pictures look like it'll be a bit tricky?

[stephane.savard]

dammit, I forgot that prop again!

[Sunfly]

Beautifull in deed.
The paint job is the cherry on the top of the cake. Wow !

Make sure you put the prop the right way before the first flight.
The last thing we want is difficulties during the maiden,we all want to avoid
mayhem and we guess ..toé-ci,toé-ci. :D

When, when, when will be the first flight. I want to be there.
:DANCE:

[stephane.savard]

Heh, it's actually not too bad to get at the prop. there's more space than it appears. Like I always say; a coroplast plane looks like crap until its first painted!

Eric, any help you can get me would be appreciated. And wait for the first flight before being jealous, with coroplast, there's never any guarantee that it will fly!

Thanks all for the good comments :)

[Sunfly]

This one will fly, I promise.

[stephane.savard]

Ha, there, I just went downstairs and flipped the prop :D Turns out it's very easy.

[Eric Marchand]

SO, maiden is ???

I've got a spare C cell, lots of Mah, I'll set it up with aligator clips and charge it up for the week-end.

Saturday ?

[Sunfly]

I have seen a case recently where an alligator clip was moving around on the glow plug and causing some glitches. It was in an helicopter, mind you, but it is something to consider.
I think a good known glow extension would be the best.
We want to see it fly,don't we ?

Cheers,

[stephane.savard]

I wouldn't leave the alligator clips on for flight. I don't know when the maiden will be, depends on weather and time available. Most likely some time this upcoming weekend.

[Eric Marchand]

A very experienced member, now president of the Jamaican branch of WIMAC international, used to start his planes with an aligator clip system. It might cause momentary glitches just after the engine has started, but then you just yank on the wires and it all comes away from the plane, without having to get your fingers near the spinning propeller. Very usefull on inverted engines...

This tip may be irrelevant to the dark side, however...What with those big canopies and whirly things up on top, an extension (50 feet preferably) seems like the way to go to me...

[stephane.savard]

Well, turns out the plane does not fly all that well. I noted a few people were taking pictures, so go ahead and post these if you want so we can all see it in a more natural setting than a basement floor :)

I had the plane balaced out at 25% MAC, which would be the standard balance point to try on a first flight and on a prototype design. Well, after a few take offs, Eric suggested it might be nose heavy. Every take off was resulting in the plane unable to climb more than siz into the air. Those takeoffs resulted in the plane crash landing in the bushes. Highlight of this was getting to the plane, upside down, and the propellor still turning happily, thwacking at the long weeds.

Removing about 2 oz from the nose, the plane did finally climb, but not anywhere enough. I had to start turning at some point, and the turn ended in some low trees. That was my last flight of the day, and there was no damage to the plane whatsoever.

Oh, and not once did the plane nose over (well, not counting the times it landed in the weeds).

If this was a "standard" plane, the current location of the CG would make me a little nervous. But, contrary to what sounds right, I'm gonna remove even more lead from the nose and move the CG to a nerve wracking position and hope for the best.

Also, I've now found that a 9x4 wooden pusher is not at all equal to a 9x4 nylon tractor prop. It simply does not give the same thrust.

[stephane.savard]

Actually, just a clarification. The plane does fly well, and once up to speed tracks very well on the runway, and then lifts off nicely and flies fairly well (despite currently having slightly over-sensitive aileron control). The problem that it does not want to climb. It also would turn rather well, except it appears to be desperately clawing for air, loses alitude, speed and then gets very intimately friendly with the nearest tree :D

[beto9]

My camera (or brain) worked as good as your plane.... forgot to put a memory card! So, we will leave the graphics for another day... when it will rise gracefully in the air, amidst the ohs and ahs of all present....

[Eric Marchand]

I think that plane will need more speed to fly well, due to the pusher effect. I'm just guessing here, maybe other pilots with pusher engine experience could trhow in their experience, but I would suggest more pitch rather then more diameter for your next prop.

Would be interesting to see how many RPM's you were getting and compare that to right way prop results for the same size ?

[stephane.savard]

I didn't think to check the RPM. I'll do so next time. The problem with more speed is that you need to get up to that speed in the first place, and without the torque of a low-pitched prop, getting to that speed will be difficult.

The feeling I was getting on those takeoff runs was that the plane just wasn't developping enough power. It's a full pound lighter than the SE5a, yet it never felt that I had the same speed or acceleration. Next time I go to the hobby store I'll see about getting a higher pitch pusher prop though and test out your theory.

At least the Airco is strong enough to withstand these rough landings. My biggest worry was the tail structure, and its proving to be very strong.

Could it be that the propellor is just stalled? It's spinning awfully fast making lots of noise but just not producing great thrust.

[Eric Marchand]

In that case, your answer wouldn't lie in a higher pitched prop, but in a larger diameter to generate more torque. Also, a pusher prop has to deal with dirty air, full of turbulence from the airframe and wing, where a puller gets nothing but clean air, so it is bound to be less effective. Going to a larger prop gives you more dirty air to push on, rather then trying to push less dirty air faster.

[stephane.savard]

I did a wee bit of research on the DH-2 and its CG and came up with almost nothing. The little I did get however is both scary and encouraging

First, I found quite a few people that have built model DH-2 and found them to be very much pitch sensitive and difficult planes to fly. Well, so far, pitch sensitivity is not exactly a problem on my own DH-2 :D And the little I did fly it, it was actually pretty stable.

So on to the second bit of news. There is very little I could find on CG. One person did talk about a free-flight version of the DH-2. He claims to have put the CG at 45% of MAC. wow. I have no idea how free-flighters usually balance their planes, is it supposed to be anything like radio controlled planes?

Next, I found a construction article saying to balance the plane at 1.5" of the leading edge. This in itself is useless information, especially since the article never mentioned the size of the plane nor the MAC. But, I tracked down who made the plans and information on it. Turns out that this is a 32 inch wingspan plane, and 268 sq in wing area. Now, I have no idea how this person calculated the wing area (i.e. did he remove the fuselage, or take into account the "cut-out" area for the propellor?). But, if I did some very simple assumptions, that would give a MAC of 4.19". So 1.5" of that would give me 35%

Conclusion? I'm going to bring my CG back to 40% MAC and see how it fairs!

[Eric Marchand]

Seems to fit with the last test flight with 2 ounces less in the nose. And, if it does turn out the CG needs to be so far back, would also explain how this becomes a twitchy aircraft.

[Andrew Fernie]

You will find a few photos of Stephane's plane at http://picasaweb.google.com/AndrewJFernie/WIMAC15June08

Andrew

[stephane.savard]

thanks Andrew! (note there is a small type in the link though, remove one "http://")

I especially like the shot of the plane going down into the field :D

I flew it again today, after removing another 1.5 oz from the nose (total removed weight so far, 4.5 oz). The plane took off without much problem, with the engine screaming at full throttle. It kept climbing and was doing fairly well. It just has massive drag and flies very slowly. It also needed full left trim, and even then it kept rolling right, so I had to hold down some aileron.

I did a few small circuits, and then decided to see if I could lower throttle. Well, the engine coughed and died. The Dh-2 did a really great impression of a brick.

It kept wanting the stall and tip, and I tried to get it back to the runway. It did make it, but hit the runway nose first. The lower fuselage popped open and the battery, foam and lead went flying! Surprisingly, there wasn't too much damage. A small dent to the nose, a bit of glue needed to the side of the nose, and I need to re-attach the fuse bottom (the rails that held the fuselage bottom panel, which doubles as a hatch, let go). When I glue the rails back in, I'll add some screws to keep it more secure.

Oh, and the left hand side tail dowels cracked. I'll glue them back up with epoxy and reinforce with fiberglass thread. Funny bit though, is that it barely shows any damage unless examined real close.

Other developments: Mick got some picturtes of the flight. The engine RPM is 13,300, and I don't think I'll try flying it with this 9x4 prop again. There's no point, it simply doesn't develop the power it should. BUT, it flies! (just so long as the stick keeps spinning hard).

again, thanks for the pictures! :)

[stephane.savard]

Oh, and I forgot to mention, Alix noticed that one of the wings has a twist in it, which is the most likely cause of some of the drag, and the extreme trim I needed on the ailerons. It will most likely be easily fixed by replacing one of the interplane struts with a slightly short one.

I'm not done with this plane yet :)

[Mick]

Pictures of the DH-2 in preparation, take-off and in-flight. I tried to get a picture of it's dive for the runway but just got a lot of sky. Not very good pictures as it is only a pocket sized point 'n press. Hope this link works.

http://cid-af8e5bcdd3500bde.spaces.live.com/photos/cns!AF8E5BCDD3500BDE!152/

[Mick]

Clearly the link did not work so try again.

http://cid-af8e5bcdd3500bde.spaces.live.com/photos/cns!AF8E5BCDD3500BDE!152/