mishal

I have just reached a stage of doing panal lines and reviting for my scratch built 73" 1/5 scale Piper Comanche 260 from plans, I put it in a scale and shows around 9.9LB (4.5Kgs) dry with OS 61FX engine, 33oz/ft2 wingloading.
I didn't stick on plans so I modified lot of things like making retractable landing gear, flaps, fiberglass, epoxy paint ..etc.

Let recall what plans saying : .40 - .61 2st with 8 LB 8 oz (3.8Kgs) 4 functions [no flaps no retracts]

Now does OS.61Fx (12x8 prop) at least can left this plane easily and do scale flying ?
unfotunatily engine mounts are " maple beams " mounted through two ply bulckheads , thats mean larger engine may not fit.

pahtreek

My Feedback: (1)

You can put any size engine you want. Take your dremmel drum sander and cut into the rails as needed to make the engine fit. Then cut a rectangular piece of 1/4" plywood and make a "U" shape, cutting out enough for the engine. Drill the holes in the plywood for the engine to mount and epoxy it to what's left of the rails. Try not to get thinner than 1/4" on the rails. After you glue the plywood and make sure the engine fits, take an epoxy brush and go over the plywood to keep any oil from soaking in.

aerowoof

you may want to look at the os 75 ax it has the same footprint as an os 61 with more power than some 90's.I am going to use one on a mick reeves hurricane that spans 80" and was for 60 size engines but I added retracts and feel the 61 would be marginal at 10 pounds.I was going to use an asp 91 but the crancase width is a bit wide for my mount and the 75 fits and has more power on the prop I will be using.

dhal22

pattern planes usually top out at 7.5 lbs for a .61. there's a lot of .91 with the same footprint as a .61.

mishal

Do you mean glueing the rectangular ply below beams to a shape like U or cutting thr ply and make U shape? .
The custom muffler droped just behind the firewall with 0.5" silicon tube through firewall in very tight space so no way to move it anywhere, I put two 1/4" tiangle birch ply on each side of maple beams for strength. I will try to post more pictures soon.

mishal

If I'm going to use 75AX then Power box muffler should be removed because of the custom muffler, do you think there will be no offset problems when connecting exhaust header to 75AX ?
You know .. these kind of airplanes have short landing gears so I can't even go more than 12" or 13" props. AX series are powerfull and accept larger props but have limited disatance between engine axle and ground.

mishal

like what ?