My R-30-X gets a new engine

[pierre sarault]

The R-30-X was designed to be a 30's type racer; the short-wing version was tested with the help of David Hamilton at the controls late last year (thanks!) and it flew well but perhaps a little short on power (?).
It is fairly heavy and its Saito FA-56B was driving a 12X7, 3 bladed prop at approx. 11,500 r.p.m..
So while I'm busy on a Consulting Contract, I decided to add a little power (about 20% more) by switching to a larger engine = the Saito FA-62B which will turn a 13X6, 3 bladed prop at about 11,500 r.p.m.. With an increase in propeller swept area of 17.3%. The weight increase is minimal at 5 grams and the overall engine installation is almost identical to the FA-56B.
I am set to brak-in the engine this week (maybe?) and wanted to share pics of the initial FA-56B -vs- the new FA-62B installation

[Ricardo]

Beautiful airplane and installation..
I've had problems with Saito on cowled installations. The carb position at the back, causes it to suck too much hot air..
As you know, hot air intake is the enemy of engine power.
This problem is accentuated with gas engines, which run way hotter.
If not too much trouble, run the engine in cowled/uncowled configurations and compare RPMs
Hope to see you at the field!

Ricardo

[Sempai-mj]

Thanks for sharing, nice plane!

[mitea_dan]

Oh, My God, beautiful plane.

[Eladio]

Beautifull Racer!! Remids me of the Gee Bee .

[briankizner]

beautiful aircraft, Pierre

[Kevin Rochon]

Very nice looking racer plane Pierre. Wouldn't a 2 blade prop be more efficient, I know it doesn't look as good but for flying purposes?

[pierre sarault]

1- Ricardo: thanks for the valuable comments - You have a point in that cold air is preferable for the carburetor to ingest (more dense = more oxygen = more power). The current cowling and firewall have hot air exhaust louvers and passageways exceeding 2X the air intake area and there doesn't seem to be much warm air stagnation where the carb intake is, but I didn't actually measure the flow and air temps. While using the Saito FA-56B and the same cowling, I didn't notice rpm / power reduction with or without the cowling (I had to test both while breaking-in that engine) I will try to see if I can route a fresh air intake duct from either the cooling air intake (cowling front) behind the prop or a fresh air intake duct would connect to a fresh air intake scoop on the side or top of the engine cowling.

2- Kevin: Thanks for your comment / question: You may be right in your comment as theoretically, a very long single blade would be more "efficient" (but impractical = ground clearance and vibration due to imbalance). As a matter of fact, the reason why fighter aircraft have 3 or 4 bladed props is (a) an attempt to keep prop tip speed lower, (b) an attempt to keep ground clearance practical while transferring more power into useable thrust, (c) to allow a lower rpm to produce same amount of thrust (real-size fighters had relatively low rpm at the prop shaft). So, in line with the above, as the Saito is a slow-revving engine (<11,500 r.p.m.) -vs- some of the two-cycle IC engines ( 14,000 + r.p.m.) I opted for a 13" dia. as it is the largest diameter propeller the Saito FA-62B will drive. You know that I prefer 3 bladed props, as, over the years I have tried both 2 and 3 bladed props (and I still have a good number of 2 bladed props for sale). The reason is that I found that for an equivalent diameter, a 3 bladed prop will produce more thrust at lower r.p.m. than a 2 bladed prop. Mind you for breaking-in I use a Dynathrust 2 bl. prop (12x8) because it is heavier (mass) and puts a good torque load on the engine.
Cheers.

[pierre sarault]

Ricardo's last comment mentioned Saito engine performance could be sometimes impacted in cowled-in engine installations by hot air ingested by carburetor.

Here is a sloppy and simplistic drawing showing the approximate airflows inside the cowling for my 30's racer; please note that hot air exhausts on each side and on top of the engine firewall as well as through 4 functional louvers on each side of the cowling aft (behind) the engine's cylinder and exhaust manifold.

In the previous test runs with or without cowling I have not noticed a difference in r.p.m. (using an optical tach).

I have been attempting to see how I could "pipe in" additional cold air directly into the carburetor's intake and I am looking at several options...not easy or obvious to implement without weight gain or external air intakes and I can't use NACA type flush air intake because this wasn't invented in the 30's...

Give myself another week...

[pierre sarault]

About 3 weeks Ago Ricardo indicated that Saito engines could lose power due to warm air ingestion by the carburator in cowled-in installations.

It took a little longer than I would have liked but I did find a solution by fashioning and installing a cold air intake and duct right to the carburator's intake.

The cold air pick-up opening in the cowling will be modified and the air intake duct will be painted black.

This setup might even contribute to positive air pressure.

Can't wait to try it!

[Ricardo]

I cannot wait to see the results! I am strugling with carb overheat in my Gas Saito 20cc... Installed a louver but had not yet tested it..

[pierre sarault]

Details, details, here are the pics of the completed installation of the forced cool air intake for my Saito 62 on my racer.

I decided to glue the air intake tube to the aluminum motor mount using self- curing RTV for automotive applications; when the tube is new this stuff flows nicely and hardens in about 7 hours. When set I removed the tie-wraps.

I then decided to finish off the cowling with a set of miniature louvers that are open to and direct the airflow into the forced air intake tube; of course that meant repainting the entire cowling (I was just going to paint where the louvers were installed ...ha!)!

So, now it is complete...now for breaking in the engine...and flying...

...time flies...

[Burning Head]

Remarquable resulta/Outstanding work

[Ricardo]

Hi Pierre, could you show more details on how you attached to the carb? Also, how did you build the tube?
Thanks!

[pierre sarault]

Hi Ricardo
I'll take 2 or 3 posts to answer your question if you don't mind as my wife is to undego surgery to-day. I will prepare sketches / dwgs which I will scan and post here later.
Specific application limitations:
-The Saito FA-62B was already mounted inverted on a set of Du-Bro aluminium shock-mounts.
- The Saito FA-62B carburator's mouth does not have an external air intake venturi and faces upward when the airframe is upright and the engine is inverted.
- The forced air intake has to divert cool air from the front of rhe cowl to the mouth of the carburator and divert it towards the mouth of the carburator without necessarily creating an airtight seal around the mouth of the carburator but close enough to prevent ambient warm air to enter due to the cool air's poaitive pressure.
- On the FA-62B there are no attachment points to the carburator other than the two main carburator bolts/screws that fasten it to the crankcase positive pressure. The carburator air intake opening is approx

Poor pictures of the intake tube (attached) show its main components but I will illustrate with drawings later-on:
- The main tube is an old Hirobo thin wall aluminium tail boom tube about 1" diameter which was gently squeezed in a vise into an oval tube,an oval opening (use Dremel tool) is cut to shape to allow the small tube to be inset at 90 degrees.
- The secondary tube is approx 5/8" thinwall tube pressed in a vise to give it an oval shape with one end (that fits inside the larger main tube) cut at approx 45 degrees to make a scoop facing forward in the main tube. The other end of the small tube is also cut at angle but on another axis/plane to create a sort of scoop that will slide over the outh of the carburator; the end of that scoop is formed to make a semi-circular "wall" (like the lip of a spoon) that prevents warm air from spilling into the carburator mouth.
-The two tubes are joined / glued using a bead of Automotive Grade GOOP or you can use JD Weld Metal/Epôxy (Hi-Temp)(Curing time will vary from 5 to 12 hours).
-An oval cap is fashioned of aluminium or other non-porous material to cap the rear end of the main cold air intake tube immediately after the junction between the side tube and the main (bigger) tube to divert maximum airflow into the side (smaller) tube.
-When the JD Weld or GOOP have set, the small tube's opening slides over the carb air intake and the main tube is attached to the Du-Bro Aluminium Engine Mount using tie-wraps or again Automotive GOOP or JD Weld (it probably is advisable to keep the tie-warps on.
Important - this is an experimental prototype cool air intake solution for this particular Saito engine and cowled-in installation; the sizes and types of tubes and the fitment in proximity to the mouth of the carburator's air intake will vary and live tests should help determine if such an installation is effective at all airspeed and engine r.p.m. ranges. One preoccupation is possible leaning (change in air to fuel ratio) of the engine at high r.p.m. and airspeed due to higher cool air pressure than would otherwise occur without this arrangement.
Next = schematics

Hope this helps

[briankizner]

off topic but-- Best of luck to madame for a quick recovery

[Ricardo]

Thanks for the reply - Hope your wife has a prompt recovery.

[Sempai-mj]

Nice scoop, best of luck with the surgery.

[pierre sarault]

Thanks guys about the exploratory surgery = it went OK; we'll see the evaluation in a few days.

Ricardo's cool air intake; If Ricardo doesn't mind using a NACA (NASA) flush air intake, there is an example of a working solution on YouTube=
search for "Saito FG 20 Air Intake Mod on P-51 Blue Nose"

Simple solution using a NACA flush air intake on top of cowling with an internal scoop attached to a flexible silicone tube (silicone exhaust tube from DuBro) tie-wrapped to the carburator's air intake venturi = seems to work fine on that video.

P.s.: I will still make those sketches for an alternate air intake solution.

[pierre sarault]

Here are the sketches for the cool air intake for the Saito FA-62B AAC mounted in my R 30 X racer.

These are sketches only to depict the priciple and installation of this version of an air intake without the use of a NACA air scoop on the cowling as the NACA laminar-flow scoops were invented in 1946-47, not in the 30's.

As mentioned in an earlier post, the Saito FA 62B AAC does not have a protruding air intake venturi tube so the source of cool air must litterally slide over the carburator's air intake to avoid complex fastening solutions involving the two main carburator-to-crankcase bolts/screws or machining the mouth of the carburator (!).

Hope this provides enough information for the FA-62B AAC version only, the Saito FG-11 (Gas) which shares the same crankcase has a different carburator with a venturi tube protruding from the carburator body probably enabling to fasten a flexible silicone tube...etc.

Operating NACA air scoop depicted on YouTube for the Saito FG-20 requires to search NACA formulas and duct shapes to arrive at your own design for that type low drag air intake.

[Ricardo]

Impressive, you can frame your sketches! Thanks for the time you put into the explanations... Let me know when you plan to go test it at the field!
Cheers,