All right, here's the deal. I like to build junk with stuff lying around and see how good it flies. I'm currently building a push/pull airplane with some gutter downspout, an old wing I have and stuff like that. The thing is that I don't have two identical motors. Right now I have a thunder tiger 40 on the front and a LEO 28 on the back. As you all now the thundertiger 40 has about the same thrust as me blowing through a straw and the 28 LEO seems to be matched pretty good with it. From what I can find the LEO 28 has about .90 bhp and the TT Gp 40 has about 1.0 bhp DO you folks think that since it is a push/pull that that will make any difference.

Keep in mind that all though I plan to fly it, I'm not trying to make it perfect, or expect it to fly like a kit or anything like that. I just like to build it and see how much fun it can be to buzz it around. It is not going to be featured at any airshow thats for sure.

Ryan

It should work, if it's not too heavy.
Keeping both motors running will be a problem.
With any luck at all it'll fly on either alone.
My push-pull Kadet at 13 pounds flies with two OS 40FPs.. on either or both.
The rear motor usually quits first.
I photo'd this this morning.. rear engine failed on takeoff.. the plane can fly on one, but the pilot didn't handle the situation properly..
Did a left turn after getting airborne, but failed to stop the turn when aimed back at the runway.
Too much elevator stalled it, and the right aileron command tipstalled it.

Thanks for the reply. Does having the engines in line cause a problem keeping them running?? Mine will be in a straight line. I notice on this model the rear engine is slightly higher than the frint engine.

The needle valve on the rear engine was clogged, and the motor was running too lean.
There's no specific reason for a rear engine to be less reliable than the front.

Hey I'm also building an inline twin SPAD. I also don't have identical engines, but only in that one is a Tower .40 and the other is a Thunder Tiger .40. The wings are a bit unconventional though, as one is rear-swept and the other is forward swept.
Hopefully my sketch shows up.

TallPaul, would you be willing to post the dimensions here. I am curious about fusulage lenth. and the lenght from the front of the wing to the back of the elavator.

Thanks

Ryan

Here's the dimensions.. the rear motor must be as close as possible to the wing trailing edge to keep the amount of ballast to a minimum.

Thanks for the reply and dimensions. They are much appreciated.

Ryan

I,ve kitbashed quite a few twins and a couple of quads but never an in line twin. Here is a simple in line kit bash of a forty size trainer I did test for a gentleman a while back. I,am the gympy one. It flew quite well with a pair of .40 K&B's, I can,t see any reason that mixed displacement is any problem.

Just one word of caution though and that is be even more careful about handling the airplane, tweaking needles etc. Any multi requires much more care in this respect but an inline airplane must be vary carefully handled as the probability of a prop strike is very high, especially when folks that only fly singles may be your helpers.

John[8D]

When you pull up, doesn't the front engine lean slightly and the rear engine richen slightly ? This often is apparrent during the take-off acceleration. That combined with the (usually modified) rear muffler can lead to a tricky tuning situation.
Therefore , place the engine that is the most forgiving, in regaurds to its tuning, on the rear of the plane.

Wouldn't the rear tank need to be placed differently than the front? I mean, if it's placed with the fuel lines exiting to the rear of the plane (straight to the rear engine), then that would put the clunk in the forward position. Anytime you'd go into a climb--such as takeoff--then the fuel could run to the front of the tank, and away from the clunk. How do you solve that problem?

There is no need at all to modify the rear engine muffler. On the one I pictured above the engine was just turned around and the stock muffler faced forward, no issues and better reliability/performance than some sort of custom pitts.

The rear fuel tank should of course be reversed with the clunk facing rear of the airplane just like the front tank and as close to its respective engine as possible.

If you are consistantly flaming out on T/O from a lean condition then you are either to aggressive on the main needle or suffer from a poor fuel tank positioning. Another possibility is your midranges are poorly set and you are actually to rich in the midrange.

.
The rear tank is installed "normally", facing forward.. with the feed tubes at the front, the clunk at the rear.
The feed lines come back to the motor and muffler.