lanpc

My Feedback: (18)

Purchased a used older 1/3 scale Balsa USA Sopwith pup. Don't have plans or instructions related to engine offset. It's obvious that offset was not built into the firewall, from which I understand some kits are not incorporated. Anyone know the offset for the model? I'm assuming 3 degrees right and 1 degree down?

Thanks
Patrick

TomCrump

While offset may be necessary, I wouldn't automatically assume that it is. A quick call to BUSA should reveal what the plans have to say.

valleyk

I also bought a balsa 1/3 pup that was in some guys attic for twenty years and completely rebuilt it. I can tell you that I played with the thrust and found 1 deg down and 2 degree right to be the sweet spot. Lots of people keep engine at zero zero but the right thrust really helps when taking off with the aid of right rudder to keep in line. Also the most important is the wing incidence which I had top wing at 0 degree and bottom at +1 degree. This is the problem with my plane is that it climbs with power on and slowly dives with power low making trimming out difficult. You really need to research this and I know there is a lot of info here to tell you what the correct wing incidence should be. Btw landing this plane is a dream in that it likes to flair automatically without worry of over correcting with elevator for messy landings that is why I have not corrected wing incidence for that reason alone.

foodstick

Here is the way I usually offset my gas motors, it is not high tech but seems to work ok.. I put center lines vertical on firewall. I then draw a horizontal line centered on where the crank should be placed exiting the cowl. Then I draw a line 1/4 above the horizontal, and 1/4 to the right of vertical..(looking at the firewall)

Then align your mounts to these holes. I get four washers about 1/16th thick. (looking at the firewall) I glue one washer on the top left, two washers on the top right,one washer on the bottom right.

Seems to be pretty close on most motor setups.... of course there are way more accurate ways to do it based on the distance from the firewall to the back of the hub... Mock it up and see how it works for you..

Alistair

don't think it matters. My 1/3 busa pup was zero zero flew beautifully. Similarly 1/4 DB sopwith pup zero zero - flew beautifully. Think it was zero zero on my 1/3 GTM Dr1 (and that has a 74cc zenoah twin) flies beautifully.

At these scales I think the engine torque effect is negligible ( a 1/3 or 1/4 bibplane has a lot of resistance)