Sethhunter

I’ve been reading a lot of posts old and new to try and pick an engine for my first gasser (scratch designed/built 1/4 scale Pfalz DIII.a biplane, a lot like an Albatros DV). Folks seem to be having more problems with gas engines than I would have expected (e.g., more so than glow). So I’m thinking my choice should be more influenced by your collective experiences than engine spec sheets. The ideal engine would be:

- Around 40cc; the plane weighs 25 lbs, 25 oz/sqft, lots of drag (rigging). Flight regime is purely scale, but a decent rate of climb is always nice.
- Very narrow; the nose of the Pfalz is only about 6” wide
- Heavy engine is not a problem; plane will need forward ballast anyway
- Run well inverted; cylinder will be out in the breeze
- Very reliable; way too many hours in the plane to risk on a temperamental power plant!

I’ve been reading about the obvious narrow engines, (rear induction/exhaust) engines like the zdz40re, R-50, Evolution G35, Roto 35 and there seem to be lots of concerns with cooling, starting, and other issues. The G38 might be a candidate although there isn’t much clearance between the prop and ignition hardware; the former engines have longer nosed crankcases. Anyone have any strong positive experiences with these engines or care to recommend another?

Does anyone think a 35cc is too small for a high-drag airplane at this wing loading?

WLJ

My Feedback: (108)

G-38 can't be beat for reliability, or ease of operation. With one of RCigns 3/8" thick carb spacers, it's quite narrow. An extension on the prop shaft may be possible.

Jake Ruddy

My Feedback: (40)

I will throw out another option because you speifically said narrow... Brillelli has a new Echo based 36cc rear exhuast that is actually narrower than a G26 but has as much power as their 40cc Scott used to sell.

I'll be honest I dont know much about 25 pounds and scale flight.. but since it is a bi-plane and you thought about a G-38 I dont see why this wouldnt work.

Bass1

The ZDZ 40 has a very narow profile but it is relatively light. The multiple prop bolts can be a pain at times though. Mine runs flawlessly. Nice looking aircraft you have there![8D]

mrbigg

My Feedback: (21)

I'd go with a 50, 60, or 62. Too much weight and drag for a 38. I have a 38 in my quarter scale DR1 and it's barely enough for my liking. Granted, I like things over powered, but you'll be at full throttle all the time just to stay airborne. You have alot of drag and weight there.

Sethhunter

Thanks very much for the suggestions.

mrbigg, do you have a narrow (or any) engine in the 50 range that you recommend? How heavy is your (1/4 or 1/3 scale?) DR I? A friend is flying a 25 lb Pfalz on a Moki 1.8. Any rules of thumb comparing 2 st gassers to 2 st glow?

Thanks again!

khodges

My Feedback: (1)

I tend to agree with mrbigg. At 25 pounds and your wing loading (which doesn't take into consideration the parasitic drag from rigging), you should go with a 50cc or so. The ZDZ 50NG is an excellent engine, small for its displacement, very powerful and will turn as much as a 24 inch prop, allowing you to fly at much less than full power for a nicer in-flight sound and the more scale size prop. With either a side- or rear exhaust, it will fit your cowl nicely. RC Showcase sells them or try Chief Aircraft, I bought mine from them, with a Slimline Pitts muffler. They ain't cheap, but you get what you pay for.

Damn fine looking plane, nice to see such an example of a not-to-often modeled bird. Post some closeups.

larry@coyotenet

My Feedback: (21)

I fly WWI planes a lot, currently I have a 1/4 D-VII, a 1/4 SE5A and a 1930s Fiat CR32. I know your Pfalz and dont think that you will find a gas engine which will fit into the cowl and have enough power to fly the plane. G-38 will not fit my D-VII so I don't think it will fit your Pfalz. A ZDZ 40 might fit but it does need a wrap around muffler which would be a bit of a problem. My D-VII weighs 18+ lbs and is overpowered with a Saito 180, my SE5A weighs the same and flys nicely with a ST 2500. A friend of mine has a 22lb Proctor N28 which flys with a Saito 180 at 1/2 throttle. You don't need to overpower a WWI model to get scale like performance. My suggestion to you would be one of the big glow engines like a ST3250 or Moki 1.8 or 2.1. If I had my first choice I would get a Laser 180 four stroke which would fly your plane well. You also might consider the Saito 2.0. Nice model of rare plane!

Larry

Marcelo Assis

My Feedback: (3)

Hello,
Torch Engines will put its 40cc on the Market soon.
It will be perfect for your plane.
Regards,
Marcelo Assis
Torch engines
www.torchengines.com.br
phone: 1 302 4070905

mrbigg

My Feedback: (21)

You'll need a rear carb engine for sure. I think your still going to have some sticking out the bottom of the cowl. A big Saito would be nice but the I'd pass on the cleanup. Electric is the best scale option but no scale sound. I don't think I could go that route. Gotta hear that motor singin' it's song.

It just hit me when I was about to hit OK. What about the RCS 180 gasser? Or the MVVS/Evolution 26 gasser? I'm thinking they are close to the Saito 180 in power. Don't quote me though.

NM2K

My Feedback: (14)

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This is a problem these days. For some reason, folks think that a 26cc gasser will keep up with a 30cc four-stroke glow engine. They will not. The 26cc gas engines produce power closer to that of a .91 glow two-stroke or a 1.20 glow four-stroke. The 1.80 and larger Saitos will eat them alive in power production and your wallet alive in fuel consumption. Sometimes it is just worth it to buy glow fuel.

If the model was not already built, I would suggest being sneaky and enlarge the diameter of the fuselage to accomodate your engine of choice. No one but a scale contest judge with documentation and calipers would ever know the difference.

The ZDZ 40 reed valve engine is an excellent choice, but as someone else pointed out, you might have to run a wrap around muffler if turning the cylinder jug 90 degrees isn't acceptable. Be sure to install a heat shield of asbestos paper between the exhaust outlet and the carb, regardless of which configuration you choose. Carburetor vapor lock can occur from other than crankcase heat.

If you could get the ZDZ in a 50cc configuration that suited your model, that would be even better. I'm not directly experienced in the realm of 25 lb. model flying, but I would be surprised if a 35cc gas engine would fly this model in a scale-like fashion. But I've been surprised before. Good luck.


Ed Cregger

Antique

My Feedback: (4)

What .91 two stroke turns an 18-6 at 9000 like my G26 ?

NM2K

My Feedback: (14)

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Always a wise guy out there...

Do the chart conversions for rpm and prop load of that, versus, oh, let's see, how about a Jett .90L on its favorite prop. Horsepower now, not thrust or some other 3D measurement that doesn't count in the real world.

Be nice, I was just about to order one of those G26 Lites from you.


Ed Cregger

STG

My Feedback: (26)

Well my OS.91FX/ultrathrust pulled an apc 15x6 in the mid 11's and gave my 10 pound Spacewalker unlimited power, allowing me to blast out of a hover with authority at sea level. The BCMA 26 or typical 26cc gas on pitts would not be more power(usable).

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I want to know more about your G26! What is true weight/performance/price with pitts muffler?


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After I posted I realized that I got way off topic. I would delete this if I could and email it straight to RCIGN1. Sorry.

Antique

My Feedback: (4)

Usable power is a G26 with a Slimline Pitts muffler..2 lbs 14 oz with ignition and battery...Mejzlik 18-6 prop...8800 rpm...17 lbs thrust...
Jett 100, 12-8 prop..14,000 rpm...Maybe 11 lbs thrust....
17 lbs thrust on a 9 lb UltraStik lite or 11 lbs thrust on a 10 lb plane..Which is more useable ?
Give me a call, ED, I have a good deal on a new one...

rollingrookie

My Feedback: (12)

For the money, www.bcmaengines.com and buy the BCMA Sport 62. It will give you the power and weight you need with electronic ignition. It will also give you the reliability a Zenoah can offer. I do not know on width of the G62 but the G-38 would be a stretch for a 26 pounder. A G45 and G62 are just abot equal.... so bump it up to the G62. Always better to have a little stick left for a windy day when things get hairy!!!

By the way, she is a beauty!!!

Sethhunter

Wow this is terrific information. I really appreciate all the suggestions. Yep it would have made sense to make the nose wider. But when I started the design 7 years ago, I just figured the engine choices would be greater. Oh well. My next project will probably be a Pfalz triplane, so I’ll have tons of engine space! The other mistake was not watching weight carefully. I wanted to build the fuselage using the laminated ply method of the original full scale. It worked well but started out heavy and just kept climbing! Next plane will be back to balsa. Thanks for the kind comments on the plane – it’s not done (wings yet to be painted, etc.). For those interested, there’s lots of pictures under the RCU scale plane forum. Not exactly a build forum; it was actually started by another modeler regarding Pfalz documentation and grew from there:

http://www.rcuniverse.com/forum/m_25...15/key_/tm.htm

Here’s a summary table of the engines discussed, size and reported power. I thought folks might find interesting. A friend who competes with a 25 lb Pfalz runs a Moki 1.8 with good performance, but 24 oz tank is marginal to complete a routine.

Engine ,,,,,,,,,,,,,,,,,Stroke,,,,,,,,,,,,,,,DISP cc,,,,,,,,POWER hp,,,,Fuel
RCV120,,,,,,,,,,,,,,,,,,,,, 4 ,,,,,,,,,,,,,,,,,19.7,,,,,,,,,,,,,1.8,,,,,,,,,,,GL OW
OS120 4ST,,,,,,,,,,,,,,,,,,4,,,,,,,,,,,,,,,,,,19.7,,,,,, ,,,,,,,2.1,,,,,,,,,,,GLOW
ST-G3250,,,,,,,,,,,,,,,,,,, 2,,,,,,,,,,,,,,,,,,32.6,,,,,,,,,,,,,3.2,,,,,,,,,,, GLOW
SAITO FA 220,,,,,,,,,,,,,,4,,,,,,,,,,,,,,,,,,36.3,,,,,,,,,, ,,,3.5,,,,,,,,,,,GLOW
ROTO 35 ,,,,,,,,,,,,,,,,,,,,2,,,,,,,,,,,,,,,,,,35.0,,,,,,, ,,,,,,3.9,,,,,,,,,,,GAS
MOKI 1.8,,,,,,,,,,,,,,,,,,,,,2,,,,,,,,,,,,,,,,,,29.7,,, ,,,,,,,,,,4.0,,,,,,,,,,,GLOW
MOKI 2.1,,,,,,,,,,,,,,,,,,,,,2,,,,,,,,,,,,,,,,,,34.6,,, ,,,,,,,,,,4.5,,,,,,,,,,,GLOW
ZDZ 40 RE,,,,,,,,,,,,,,,,,,,2,,,,,,,,,,,,,,,,,,39.7,,,,,, ,,,,,,,4.8,,,,,,,,,,,GAS
3W 50CS,,,,,,,,,,,,,,,,,,,,,2,,,,,,,,,,,,,,,,,,48.7,, ,,,,,,,,,,,4.8,,,,,,,,,,,GAS
BCMA-ZEN62,,,,,,,,,,,,,,,2,,,,,,,,,,,,,,,,,,62.0,,,,,,, ,,,,,,5.0,,,,,,,,,,,GAS
EVOLUTION 45 X2,,,,,,,,2,,,,,,,,,,,,,,,,,,45.0,,,,,,,,,,,,,5.1, ,,,,,,,,,,GAS
ZDZ 50 NG,,,,,,,,,,,,,,,,,,,2,,,,,,,,,,,,,,,,,,52.2,,,,,, ,,,,,,,5.7,,,,,,,,,,,GAS
REVOLUTION R-50,,,,,,,,,2,,,,,,,,,,,,,,,,,,52.2,,,,,,,,,,,,,5.7 ,,,,,,,,,,,GAS

Summarizing comments from you guys and others:

26 lb Albatros very marginal on 3.2 hp (ST G-3250)
25 lb Pfalz DIII.a very good on 4.0 hp (Moki 1.8)
18 lb DVII good on 2.8 hp (Saito 180)
17 lb SE5a good on 2.1 hp (OS120 4st)
22 lb N28 good on 2.8 hp (Saito 180)

For fit and positive recommendations I think I need to look at the ZDZ 40 or 50 NG. The Moki 2.1 seems like a real power house but fuelish. Does anyone know who’s distributing Moki in the US these days? (No distributor is listed on the website).

Any comments on the fuel consumption of the ZDZ 50 at <50% throttle?

Thanks again everyone!

Bass1

If you have an extra $2500.00 on hand this might be the ticket!

Sethhunter

Now that's cool. Anyone running one?

NM2K

My Feedback: (14)

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Let's talk via PM or email. Your choice.


Ed Cregger

mrbigg

My Feedback: (21)

From what I've read, the Saito 180 doesn't hold much of advantage over a 26cc gasser. Consider the intial high price, the high price fuel, the clean up, the expensive glow plugs........The Saito just isn't an option.