BadSplice

My Feedback: (1)

As I dig through the mounds of wreckage and leftovers from my RC career so far, I have started to try to use up some of it on experimental projects. This is my latest frankenplane, so far I have the body from a PZ Trojan, the wing from a GeeBee Senior Sporster from Hobby Lobby, and the leftover canopy I didn't use on a Great planes Easy Sport. I think the effect is something like a P-47 mated with an FW 190.....

The issue I'm struggling with is the horizontal stab. What is in the pics is a leftover stab from a GWS Formosa. Its a bit smaller, in length and chord, than the original stab from the Trojan, but the elevator has more surface area. But overall it seems too small. I went around to some of my other planes, and did some measurements of wing length/ Stab length, and then started to mock up a stab out of depron based on that, but it seems too big. (last pic)
Can anyone tell me if one of these stabs might work, or if not, what else might work?
So far, the plane is:
Wingspan = 48"
Length(firewall to rudder hinge) = 30" (w/cowl and rudder = 34")
Formosa Stab = 15 1/2"
Homemade stab = 19"

Im not a math wiz really, but is there a simple formula for determining Stab size from wing size? I had also thought of making the Fuse a little longer, but that would be a last resort. With the way the fuse tapers it would be hard to make it seamless, besides keeping the tail straight.

BMatthews

If you check the sticky at the top of the forum thread listings there are links to some tools. One of them is a CG location calculator. Your middle picture with the sunburst stabilizer will prove just fine for this kludge. Measure it as needed for the calculator and I'm sure you'll end up with the CG in a normal mainstream location. It suggests between 5 and 10% be inputted for the stability margin. If you're a fairly competent flyer after producing all that carnage then do a couple of calcs with 8 and 4 inputed for stability% values. That would be a good max forward and max rearward range to work between until you get a feel for the model.

BadSplice

My Feedback: (1)

Thanks! Using the stab in the middle pic will be the easiest, and it is nice and light. I think I'm a reasonably competent flier and I think I'm a fairly competent builder, but I am only just scratching the surface of design I have arranged the wing so it is at somewhere between 0* and +1* in relation to the H-stab. For the test flights, I will go with the thrust angle that is already built into the Trojan's firewall.

BMatthews

That wing looks like the sort of thing that comes with a flat bottom airfoil. Keep in mind that the flat bottom is not what you use for setting the wing incidence. You need to use the point at the most forward part of the leading edge to the point on hte trailing edge as your reference line. If you set the flat bottom to +1 you may very well have +2 to +3 of actual incidence. IN any event I'd set the wing at +2 to the actual centerline. That would be a better beginning point for this sort of model.

BadSplice

My Feedback: (1)

The wing is semi symmetrical. But what I did to set the incidence was to use the bar from a GP incidence meter clamped to the wing, and extended with a straight edge to align with the gap for the stab. ( I need to get some new batteries to actually use the laser part of the meter) I realize its rough, but I thought it would get close enough to start, and I will be able to make adjustments later if needed.