non-permanent wingpanels connection

[DS]

Not sure if I am posting in the right place, but I guess that people involved with giant planes might have an answer regarding this transportation issue.

Upto now I have been building small parkflyer sized planes that could fit in the car without the need of disassembly. I now am planning to build a somewhat larger model (not really a giant scale one), and will construct the wing out of a centerpiece and two wingpanels. I have done multiple search on this forum, but don't really know what words to look for.
I am planning on using a single carbon tube as spar, and need to find a way to connect the outer wingpanels to the centerpiece. It will be a single motor plane, so only the aileron servos will need to be connected with extension cords to the centerpiece.

Anyone to point me to an appropriate thread discussing the different possibilities to interconnect wingpanels?
Thanks

[AmpAce]

DS,

You might try searching for "wing joiners" or "wing attachment". I can't come up with any specific thread that addresses this, but there are several good ways to do this.

Some of it depends on the design of your plane. If your plane doesn't have lift struts, the joiner will have to be much stronger, as it will have to support the lifting loads, (and negative loads), as well as keeping the wings from separating from the fuselage. If your plane has lift struts, just a couple of bolts through well supported ply ribs should suffice. This keeps the wings attatched to the fuse, while the lift struts support the lifting loads.

Since you are using cf tubing for the spars, you should be able to find a slightly larger cf tube that will just slip over the spar. If you have two cf spars, so much the better. You can anchor the larger tubes in the center section, and let the spars slip into them, so the wing panels will snug up against the center section. The spars should slip into the center section approximately half of the sections width, assuming it is roughly the width of the fuse, to provide lots of strength. The wing panels and center section are normally bolted together. Blind, or "T" nuts are handy for this.

Just be sure you have plenty of support where the tubes slip together, and it might even pay to bind the outside of the outer tube, near it's end, so it won't split under load. Also, you need at least two points at the joint between the center section and wing panels, that prevent them from rotating in relation to each other. If you use only one spar, just a dowel into a hole, or two shrort sections of tubing will work for the second point.

Sorry about the long-winded post, but hope it helps a bit.

Best of luck with your project!

AmpAce

[DS]

Thanks for the explanation. Much appreciated.

The plane will be a twin boom pusher (or tractor, or both, like the Cessna Skymaster). I plan to have the section between the booms (including booms) as the centerpiece, and from boom to wingtip as a separate wingpanel.
I also plan on using a single CF tube for the main spar that I would slide into the center section. The tube will then extend both sides of the centersection, I'll then slide the wingpanel onto the extending CF tube. As you mentioned, I'll be using additional dowels to prevent rotations of wingpanels relative to the center section.

As for bolting the wingpanels and center section, does this happen parallel to the spar (through the outer ribs of wingpanel and center section). Or should this be done perpendicular to the spar (through the wing thickness, using some kind of lips from both sections that intersect)?
The main purpose of this is to keep the wingpanel and centersection together, as all the lifting loads will be handled by the single-piece spar.

Thanks.

Edit: Did some searching with the proposed words, a lot of information regarding the CF tubes, but didn't find anything related to the attachment (retaining?) of the wingpanels to the centerpiece.

[Ercoupe Ed]

DS,
Awhile back I bought a Hangar 9 clipped wing Taylorcraft ( 1/4 scale) that calls for epoxying the two wing tube sections together in the center tube in the fuselage.
I thought this wasn't what I wanted, so I have decided that after sliding the wings on, I am going to drill through the wing tube sections and use at least 4 to 6 aircraft bolts with locking nuts to hold the wing sections together.
The other mod I will make is to put a turnbuckle in the center section also to help hold the wings together.
I could probably do without the bolts, but they will be redundancy.
I also have a partially scratchbuilt clipped wing T-Craft of Duane Coles airplane I started building of Duane Coles airplane, and that plan has T6 aluminum tube wing spars that slide into a center tube in the fuselage, and held together with a turnbuckle.
The plans are from RCM and the airplane and build were featured in an RCM issue back in the mid 80's.
I also plan to wrap just a bit of masking tape around the wing tubes to get a firm fit inside the center tube.
I own my own full scale airplane, so I have a lot of extra bolts, etc, and just decided to use those.
This way, I can unbolt the wings and make it much easier to transport them.

Is this what you are trying to do?
After thinking that you will be using carbon fiber tubes, you might consider sanding the center tube inside the fuselage slightly and epoxy some small flat hardwood blocks( maple or spruce on the top and bottom of your center carry through tube so the bolts won't cause the spars to crack from vibration.
So you get an idea of what I mean, they( the hardwood blocks) will be like spring pads on a car axle.
Then use a turnbuckle also, or just go with a turnbuckle, possibly two,
one on the front wing section, and the other on the rear wing section.
This way, when you're done flying, just unbolt the wings, slide them out , pack them up and go home!
It will also make for easier storage in less pace at home.

Ed

[AmpAce]

DS,

Ed's method should work well, although I would be very careful in bolting through the cf tubes. They split very easily, and also might tend to wear the bolt holes rapidly. I think I would bind them around the outside, with thread, fishing line, or very strong tape, and glue on whatever method you use, as well as using the wood blocks as described by Ed. If you bolt through the cf tubes, another thing you can do to greatly strengthen the spars is to slide a short section of close fitting dowel inside the smaller tube, and glue it in place, at the point where your thru-bolt will penetrate the tube. This will give your bolts a lot more bearing area, and you can tighten them down more without cracking the cf tubes.

If you can get access to the interior of the wing, it is preferable to bolt through two well reinforced ribs, parallel to the spar. If you can't do that, then some kind of a lip would be O.K., as long as it is well attached to the structure. You should have bolts in both the fore and aft part of the wing.

Sounds like you are on the right track, and have most of your design well thought-out.

Interesting project, keep us posted!

AmpAce

[Butch777]

Like AmpAce said; CF tubes may split easy.

I'm building a 91.7" EPP plane with CF tubes for the wing spars and pondering how to connect them. I found a composite tube that fits inside perfectly.
But! When I tried to insert the composite tube into the CF tube, the CF tube split!
I had not sanded a burr on the end of the CF tube and just forced the composite tube in like a dummy! And I'm a fiberglass repairman by trade and know better.

I have to trim a bit off the tubes anyways and I'll just use that end on the outboard side, so I'm ok. But seeing how easy it split, I'll wrap some CF tow around the ends of the tubes to keep them from splitting. Butch

[portablevcb]

When I have used CF for spar or connecting sections I use an Aluminum tube for the other section. A slip fit.

Connecting can be done with through bolts. Fill the area of the CF tube with a wood dowel and epoxy it in place, then drill through.

I have used brass 'tabs' and bolt to both sections. I like blind nuts and round head hex bolts.

Another way, if you have a hatch access, is to use a spring with hooks to tension the panels into the fuse.

If your plane has rigging, the rigging will hold the sections together.

For the most precise fit, use tapered pins (can be secured with nuts on the narrow end if needed.

charlie

[eye4wings]

Another (cheaper and perfectly adequate) method of connecting the outer panels once located is to use a wire pin bent from piano wire (20 - 18swg) running into a short brass tube in the panel and through a thin loop projecting from the centre section. This pin is harder to lose in the grass if your fingers are cold and a slight kink in it holds it in the tube by friction. In the event of a crash the loop pulls out of the centre section LE with minimal damage.

I also use audio 5-pin DIN plugs and sockets which connect aileron servos and landing lights in in the same action of plugging the wing in. Some modellers in the LMA use D9 connectors for this, but the pins of these are smaller.

Hope this is of interest.

[DS]

Thanks for all the replies so far. I'll need to re-read them a few times, as I don't get everything.

I have attached a few pictures showing the testing-rig I built some weeks ago. I have omitted the spar. In the pictures you see a wingpanel, one boom and the wing center piece. Both the wingpanel and center section have two lips that overlap each other inside the boom. A blind nut is glued inside the boom. All I have to do is slide the boom and wingpanel over the spar and fix all with two 3M screws.

This was my original idea, but since I wasn't sure if this was the way to go I prefered to ask here to get some ideas. Reading from your replies I understand my idea was not such a bad thing after all.
Since there are two lips (one in front, one behind the spar) would this be sufficient to prevent rotation of wingpanel and center section in relation to each other? The lip is made of lite ply and the extending piece as well as the part inside the wing are both approx. 1 inch. The inside part is held by two ribs.

Thanks again for the feedback.