Building Tips (Straight Wings.. How?)
First you need a flat building surface. We like to use a good flat board with
fresh cardboard taped on for the pins to stick in. A hollow core door panel is
very flat, but may be somewhat inconvenient due to its size. Appliance stores
will usually let you have refrigerator boxes. One of these usually has a lot of
smooth cardboard.
Place the plans over the board and lay wax paper over the plans. Pin in
place at the corners.
The lower spar typically is pinned in place over the plans and everything is
aligned on that. The spar material is typically too long. Do not cut it until
later.
Make small 90 degree angle braces to help in aligning the wing ribs. 1 inch X
2 inch aluminum "angle iron" stock cut to 1 to 3 inches long makes good
braces. they do NOT get glued to the wing... they just hold things straight
while the glue dries. Spring type clothes pins make good clamps to hold an
angle to a rib.
Check the wing ribs for proper fit to the spar. If the slot needs to be deeper
it is easiest to glue a bit of sandpaper to spar stock which will be later cut
off, and sand the slot open. Don't forget that the sandpaper adds thickness to
the spar stock... check depth in the location the rib will be attached.
Align and glue the wing ribs to the lower spar. (beginner's planes typically
have flat bottom airfoils, so the bottom of the rib should be flat on the building
board.)
The upper spar goes in next. Again make sure all the slots are the correct
depth. Place the spar in the slots and glue. (glue first if not using CA)
Add the trailing edge.
Add the leading edge.
If the structure was held straight for these steps, the wing panel should come
out straight. If the wing has sheeted sections it is best to sheet the upper
portions after the lower portions with flat bottom wings. the flat lower sheet
helps prevent inducing a warp while putting the upper curved sheet on.
Also... if the wing has "shear web" between ribs be sure the wood grain is
vertical and put the web in after the bottom sheeting and before the top
sheeting. (easier and locks the wing alignment very firmly.)
Note: these steps are not appropriate for the little Guillow's rubber powered
models... they have to be built on the leading and trailing edges, instead of
the spar. Some models may need differing techniques, and the kit instructions
take precedence.
We
notice that when we are building, if we center everything to the lines; nothing
touches and we have to move to one side of the line or the other. Should
we treat
the lines as a guide and build to the cut pieces or what?
Answer:
The paper of the plans will actually shrink or stretch up to 7% with changes
in humidity, and with age. Due to this, they should be regarded as accurate
guides, with the balsa wing ribs being considered more accurate for their
size. (They shrink and expand with humidity too.) It is unlikely for the plans
to actually be more than 2% off from their size at time of printing unless they
are VERY old. The slight discrepancy in wingspan will not cause much
problem, so use the plans' spacing for the ribs.
It is sometimes necessary to sand off the trailing edges of some of the wing
ribs to have the trailing edge stock meet all the ribs at the same time. It is
less likely to be needed with the leading edge.
The plane will actually fly better with 2 wings that are slightly different size
due to the sanding of the ribs to mate with the trailing edge stock than it will
with a wing that is warped by forcing the stock to bend and meet all the ribs.
It is unlikely to give a full square inch difference in wing area on a wing
panel when you adjust the wing ribs to meet the trailing edge stock.
Dubai RC Hobbies