Engine for a 53" span bipe?
 

I'm scratch-building a Pitts Special, from Nick Ziroli plans from 1967. The plans don't provide finished weight, but the sketchy instructions that came with them suggest a .45-.60 size two-stroke. (Specifically, those instructions say the prototype carried a .46, and that was "minimally acceptable.") And, remember this was all said in 1967.

The longer wing-span is 53", the shorter is 44", and the fuse is 45" long. Similar sized ARFs on the market generally recommend .60 sized two-strokes or .90 sized four strokes. The airplane is balsa and ply built-up, mostly sheeted with 1/8" balsa, and I'll cover it with some brand of film.

My objective for performance is primarily reliabilty. I'm not looking for a screamer, but I don't want to regret under-powering it. Also, I take some pride in trying to be economical - I'd rather spend less money than more, although I don't want to be foolishly cheap about it. I don't have a strong preference between a 2-stroke or a 4-stroke.

I'm considering the Tower .75 two-stroke. What do you guys think?

RE: Engine for a 53" span bipe?
 

Go with a 60 to 75 size engine. I have a Global Tecate Bipe with a TT 46 Pro and it's ok. My Lou Andrews Aeromaster flew great with an OS .61 FSR

RE: Engine for a 53" span bipe?
 

The Tower .75 would provide more than enough power....:D

RE: Engine for a 53" span bipe?
 

Magnum .91's weigh about the same as most .60/.75's, and they're on sale right now for $129. I like them so much I have 2 of the newer XLS, and an older ASP(a little heavier). But the XLS .91 with a 16x6 would do nicely. I have it on a 9.5 lb fun fly that will rocket out of a hover.

RE: Engine for a 53" span bipe?
 

That size plane begs for the right sound too. Sheldons Hobby recently had Enya .90-4c for less than the same size magnum. Enya engines last a very long time. The Fox .60 was the highest powered .60 2 cycle in a recent M.A.N. shootout. Their .75 uses the same design and weighs no more. (it will be inside a cowl won't it?)

RE: Engine for a 53" span bipe?
 

Most 2 strokes put out today have a bit more power than those of 1967. I suspect a .46 would be just fine. The smaller biplanes fly a bit squirely at times and can be a bit challenging to fly. I'd start with a .46 2 stoke and go from there. But weight and wing loading is a major factor in selecting the engine size. I'd suguest weighing your airframe and see what you have to work with. Do you show an wing area?

RE: Engine for a 53" span bipe?
 

Biplane: lots of drag for the increased wing surface area. Personally, there is nothing sweeter than a 4 stroke engine in a biplane. If you can fit one, the Saito .91 would be a great lightweight choice for this aircraft.

RE: Engine for a 53" span bipe?
 

Those are great suggestions. Thanks!

I'm persuaded by those who say I have to put a 4-stroke in this bipe. What's the best value in a .90 size 4-stroke? Is there any such thing (worth buying) for under $200?

RE: Engine for a 53" span bipe?
 

Since power and weight are of concern for this bipe, a used Saito .91 is a good bet or a new Magnum 4c. However, if you need a littlte extra ballast and want the power of a Saito 100 in a .91 package than the TT .91 beats most 4c .91s hands down.

RE: Engine for a 53" span bipe?
 

I will second the thoughts of using a 4-stroke. Enya, Thunder Tiger or Saito are all very good choices. Otherwise I would go with a nice 60 size two stroke like the Enya or Thunder Tiger.
I have a Great Planes Sportster Bipe and it is under powered with a 46FX on it, even though it is light, it just has a lot of drag. My Saito 91 will be going in it for next season.
Remember you always have the throttle.

Fuelman

RE: Engine for a 53" span bipe?
 

O.K., I'm getting close. I'm looking at a Saito FA-80 or FA-91S. They're only about $10 apart in price, so I should go with the .91, right? Then, is there a better way to buy a new one than directly from Horizon Hobbies? Finally, is there a Pitts-style muffler available for these?