avalanchehowler

Hi,
I'm currently building my first kit a 4* 40. I have finished the wings but now that I am trying to fit them together with the diehedral brace in it has become apparent that I put too much diehedral on the first wing ribs on each wing. (my card table is bowed). So when i put the wings together there is a 1/2 cm gap between the tops of the wing halves. I'm wondering how to fix this.

Should I just pour epoxy into the gap? I really don't want the amount of diehedral that i would have if I altered the diehedral brace to fit the two wings "snug."

Thanks

LouW

Cut a wedge of balsa to fit the gap and glue it in place.

CP140

Just to clarify, are you saying you're winding up with that much of a gap when one wing is flat on the table and the other wing tip is propped up the appropriate amount at the other wing tip? I seem to recall that the 4*40 instructions say that you can vary the amount of dihedral by a certain amount.... if you go to the maximum "allowed" dihedral, how does your gap look then?

A couple of questions for you now...although I'm pretty sure you'll have already scratched your head over this already.....Are your leading/trailing edges or the bottom spar running into each other before the root ribs and thus holding the wing halves apart?(I had square ends on mine and had to bevel them slightly to get a good tight join) Is the sheeting on the bottom of the wing flush with the root ribs? Is there a bead of glue at the second rib stopping the dihedral brace from sliding in all the way?

Like I said, I'll bet you've already looked at these issues.... just tossing some ideas out....you might be able to cut a dummy rib to fill the gap between the two root ribs...don't know how well this would work though.....

avalanchehowler

thanks for the replies! I have made sure that the spars are sanded down even and everything but there is still a gap. At the max amount of recommended diehedral there is still a .4 cm gap. I had also considered a dummy rib and I think that is what I'll do.

GrnBrt

My Feedback: (5)

a dummy rib will work and all you have to do is sand it to the right angle, have fun and good luck and get a better building table!

MinnFlyer

My Feedback: (4)

Yea, don't worry about it.

And stop using those silly dimentions! Feet and inches are what set us apart from the Third World Nations.

mjschu

I too am building a 4 Star 40, and just got done glueing the 2 wing halves together. I had a simular problem with having a gap on top of about 1/16th of an inch wide. I used 15 minute epoxy on the dihedral brace but for the gap between the main wing spares, I used elmers probond polyurethane glue. The amazing thing about this glue as it's setting up it actually expands and fills in gaps. ( You can watch it expand!) It appears to be very strong and sandable. I hear gorrilla glue is simular.

Time Pilot

Ain't that ironic, I was about to post a topic like this with but not enough dihedral.

The last wing I built didn’t end up with enough dihedral and to fix it as per the instructions would involve sanding the root ribs too thin. I built the kit as per plans and was being very careful using the dihedral gauges provided with the kit. I'm fixing this by gluing another rib to the root rib and sanding it down to get the right angle, but I could have saved myself some grief had I used a different technique instead. I wouldn’t have cared so much had this been an aileron ship, but having only a rudder, I’m counting on the generous dihedral to keep things level.

The manufacture (Great Planes) was very quick to reply to my email saying it wouldn’t matter too much, but I would be more comfortable knowing it was built to specs.

I’ve not used this method, but will definitely try it next time unless someone suggests better. It sounds like it may be a bit difficult to rig up, but the time will result in a good wing.

This technique sounds like it would work best with a flat bottomed wing.

Higley suggests building one side of the wing on the plans then removing it and then securing it right on the plans next to its other half where it would normally be joined later. Make sure the wing tip is off the table as per instructions and make sure the wing is inline with one about to be built.

Then, cut or sand bottom wing spar, the lower TE and LE (assuming the bottom of the wing is sitting on the plans) so that they mate with the already built wing. When they do, glue them to the root rib of the built wing and pin them to the plans. Then go about finishing building the wing.

Any comments on this technique?

phread59

Did you glue the wing together yet? If you didn't I would suggest fitting the dihedral brace some. And try to get the wing halves together. If you are already glued. Make a balsa wedge or rib and glue it in . Then using heavy fiberglass cloth around 4oz weight and glass the joint to at least the first rib out from the joint on both sides. You can glue it with thinned 30 min epoxie. Rubbing alcohol will do for thinner. Or glue it down with thin CA. You must get a flat surface to build on. Here is a suggestion. Go to a lumber store or a Lowes or whatever. Bet a sheet of 3/4" MDF (medium density fiberboard). Cut the sucker in half down the long way and you get a 2 x8 foot board. Take some deck screws 1 1/4" and screw both directions into the MDF. From top and bottom. Find a set of folding table legs. I got mine at a Cole's hardware store. Mount the legs and find something that you can push pins into. I just screwed some homasote to the top of my bench. You can glue ceiling tiles on or whatever you can find. If the bench is too long just cut it down. The table is semi portable and stable as hell. It will be plenty flat. I hope this helps.

Mark Shuman