I need help with converting a control line plane to an rc one.

I recently aquired a control line plane by Sterling Models, Stearing
PT-17. The wing span is 32 1/4 ", Length 24", for .19 to .35
engine. It is a Bi-plane with a monocoupe fuselage. I'd like to
convert it to an RC plane. I thought I could just hack the upper fuse,
which I did already, tear out the control line stuff, and put the fuel
tank back in the front w/ the flight pack and servos behind it.
However, I talked to a guy that said that "a .15 to .20 would be
plenty enough engine for a conversion." He said "I might run into
problems in with the wings. Since it is a c/l kit, the wings are FLAT
and you would need dihedral to make the plane more stable. Also you
would need to add down thrust and maybe change the incidence of the
tail. When the kit was designed, installing a radio in it was out of
the question as the radios were HUGE".
Well, I've removed the covering, chopped out the top for the servos
and now I'm stuck. I don't know if I have to lengthen the tail a
couple inches, change the engine mounts, or what. I've built several
planes but never anything like this. I dont know how to post pics here
to show what it looks like but I have a bunch to email if it would
help.
Any help is appreciated.
Matt Trickey
Reply to
matt_trickey
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You wont need to change the dihedral, or the tail length.
You WILL need to come down in power,and get the CG right. And fit ailerons.
You MAY need a bit of down and right thrust. But I wouldn't bother to start with, until you have it trimmed out. In particular with zero dihedral teh side thresut may not actually do very much.
My 32" span biplane flies on the electrical equivalent of an 049, BTW:-)
Control liners were notoriously draggy due to having to drag the lines around.
So, the most important thing is ailerons and the CG. You will NOT be able to control it in rudder alone, and if the CG is wrong - it needs to be pretty far forward for a bipe - it will also be uncontrollable.
Reply to
The Natural Philosopher
| I recently aquired a control line plane by Sterling Models, Stearing | PT-17. The wing span is 32 1/4 ", Length 24", for .19 to .35 | engine. It is a Bi-plane with a monocoupe fuselage. I'd like to | convert it to an RC plane.
Sounds interesting.
Make sure the plane is actually symmetrical! Many C/L planes have one wing larger than the other one, because it either 1) doesn't matter or 2) actually flies better that way.
(and if the wings don't match, things become a lot harder ...)
Reply to
Doug McLaren
Open an account with photobucket
formatting link
or similar, (it's free) upload the pix, and post the details here.
Trefor
I dont know how to post pics here
Reply to
Trefor
All biplanes have one wing larger than the other. The top one is usually larger than the bottom and many times on wing is swept back and the other isn't. They wouldn't fly very well if both were the same size. Concerning CG , it doesn't matter if it's a bipe or whatever , they still balance at 25-30% of the mean aerodynamic chord. Some do go as far as 33% but only after starting at a more stable balance point. Ken
Reply to
ken day
What he means is that in some control line planes the left wing will not be the same size as the right wing. This is a lot more of a problem than the top and bottom wings being different.
Incidentally, not all biplanes have one wing larger than the other. Lots of biplanes have equal wings on top and bottom, and they do fly very well.
Reply to
Robert Reynolds
Robert, you're absolutely correct (about bipes ;)) However, a major consideration is the decalage (incidence delta between the upper and lower wings). The top wing on a positive staggered bipe must be set at a higher angle of incidence than the lower wing. That is essential in order to cause the nose to drop in a stall. Improper decalage with a positive stagger bipe will cause the tail to drop in a stall with nasty repercussions. The good news is that if the bird was correctly built from the plans it probably has the correct decalage. BTW,if you don't add dihedral to the wings you *must* add ailerons because it won't turn without them. Good luck :-)
Reply to
Ed Forsythe
I stand corrected, just wasn't thinking about the wings being different from side to side.
That should have read MOST biplanes.
Reply to
ken day

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