-=> Keith Nunnery was writing to All on 03-21-95  22:03 <=-
 KN> Hello,
 KN> I'm looking for plans to build a power pod for a glider. Any
 KN> good ideas?
What size? Sig sells a little kit for .049's for about $5.00. It's
so simple, you could look at a picture of it and scratch your own.
I recently built one for a .10 engine (lifts std. class sailplane).
Very roughly, it looks like:
                        Side view                    Front View
                     ________________________
  Side mount         -------- - - - ---------            ||||
  engine  here  -->        | |    | | 2 oz tank          ||||
                     ______|_|_ _ |_|________            ||||
  1/4" spruce eng.-> -----   - - - - --------            ||||
  bearers and internal    \| |    | |                    ||||
  frame.                   |        |                    ||||<-1/8 lite ply
                           | |    | |                    ||||      exterior
  countour base of pod     |         \                   ||||
  to airfoil shape         | |    | |  \                 ||||
                    ->   / | |    | |    \              / || \ <- Tri Stock
1/8 lite ply > ===================================  ===============
Flat on your table, build an internal frame of 1/4" spruce to fit your
engine and tank. Allow as much extra space for your tank as possible,
to allow for some foam vibration isolation. Alternatively, you can
leave the rear portion of the pod solid, and side mount the tank (strapped
on a piece of foam). Extend spruce frame posts to the base. The spruce
frame is sandwiched on both sides with 1/8" light ply. Trace the shape
of the airfoil on your plans. This will be the shape of the bottom of
the pod, and will hold the lite ply base plate to the airfoil shape.
The wing hold down rubber bands slip over the top of the base to hold it
down. Set the thrust angle a few degrees positive (up). The shorter you
make the pod, the less thrust correction you need. Thrust angle is not
terribly critical. However,a shorter pod will also be more rigid; less
vibration.
Minimizing vibration is important. An engine on a pod is less firmly
mounted than on the nose. Vibration causes fuel to foam. The problem
is exacerbated when using a small fuel tank. Carefully balancing your
prop will make a BIG difference.
Another technique is to simply cut the pod from 1/8" sheet aluminum.
Instead of building a flat base, drill holes to mate the joiner rod
rod and guide pin at the wing root. The plate is sandwiched between
the wing halves when assembled. This is obviously for 2 piece wings
only. It is not as rigid as I like, but I have used it successfully.
Lastly, I have a copy of RCM from about 20 years ago with plans for
one of Harly Michaelis's sailplanes. He had a power pod which substituted
for the hatch cover. It was a regular nose hatch plate, with a ply
engine mount/fuel tank sticking up. Nice idea, if your plane needs
nose weight, but it was butt-UGLY!
If you're using a reed valve Cox .049 I'd just buy (or copy) the Sig pod.
Bye now,
Bruce
___ Blue Wave/QWK v2.12
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