Misc Wing Const Photos

here are some wing construction photos;, mixed Millennium 2, Profile Bearcat, and BBQB Bearcat. You may find some useful ideas.

Thank you Al for the pictures. Can I ask you a couple of questions on the pictures?

1) Can you explain the last picture? I am a little confused on how you do the flap horn box.
2) On some pictures you show a small jig with the center section. Do you glue the center section together first and then move to the large jig.
3) Can you describe your wing jig?

Thank you Al!

Steven,

The last photo is a "lucky box". I don't know why it is called that, but, in any case, it is used, one on each flap, where the angle of the trailing edge or dihedral are sufficient to cause binding in the flaps when the controls are fully deflected. It seems we can get away with 3-4 degrees of misalignment but more usually requires either double flap horns or lucky boxes, with lucky boxes being the preferred choice, as double flap horns always involve some asymmetry,

There are two lucky boxed shown. The right one is already installed in the flap and will be sanded and filled until it disappears. The next item to the left is an uninstalled lucky box consisting of a 1/32" plywood floor, a 1/8" balsa frame which fits around the flap horn and a 1/32" ply top. The ply top is the other item on the left. This assembly is installed in the center of a 3/8" flap and 1/8" balsa added top and bottom to fill the top and bottom holes in the flap. The whole mess is then sanded flush with the top and bottom and top surface of the flap. The idea is to provide a bit of room for the flap horns to move sideways as the flaps move up and down. The 1/8" balsa spacer is to barely provide room for the flap horn in the box. The ply layer in the top and bottom of the box are wear surfaces and eliminate any vertical play in the box. The box tapers with no room at the front for sideways movement at the front. This is because of the character of the flap travel as the flaps move. When the flaps move up, the flap horns tilt toward the fuselage due to dihedral and trailing edge sweep. When the flaps move down the flap horns tilt away from the fuselage, not much, but enough to cause the controls to become "springy" if the trailing edge angle exceeds about 3 degrees.

As for the short center section assembly, yes, I do assemble the center section of my wings complete with the finished control system, bellcrank mount, bellcrank, leadouts, flap pushrod and flap horn, glued and soldered to a finished state. the completed assembly is then mounted on jig tubes and the rest of the wing structure added. It is much easier to build the control system into a stub section of the wing as opposed to trying to bury it later when the parts are harder to handle in an assembled wing.

My jigs consist of one base of 3/4"x4"x60" particle board or MDF. The vertical supports are 4"x8"x3/4" MDF or particle board. The vertical supports are chosen at 8" to provide enough height to install a completed landing gear on the jig. I usually get a complete set of jigs, including the fuselage jig, by cutting up a 3/4"x12"x72" shelf from Home Depot for less than $10.

One of the final photos shows the center jig support penetrating the bottom surface of the wing to continue to support the jig tubes while the final sheeting is taking place. When the wing is finished , the center support is removed and the holes repaired. All gluing of the wing skins takes place with the wing rigidly supported at the center and both tips.

Another photo shows the final bottom sheeting going on. I attach that last sheeting at the spar and then flex the sheeting away from the wing while at the same time pushing some of the sheeting against the ribs. The actual gluing is by running CA down the portion of the rib touching the skin. With a flash light and some Patience it is possible to glue every smallest bit of rib and sheeting. The result is a very secure job of sheeting which is a bit difficult to describe. The concept was BBQB, to build the entire wing with CA, in one sitting, with no drying period required for slower drying glues.

Wow,
Thank you Al for the answers! Your construction methods are simply amaizing! Wow!

Al;

Big question for me is the sheeting with CyA.

I can see how you can do the molded LE. And, I can see how you can sheet one side by having access to the ribs and sheeting when one side is open. My big question is how you are putting down the final panels, how are you gluing this down with CyA?

Al,
If this is your Bear Cat, why is Richard doing the glueing Ha!Ha!
Tell Richard to knock if off. And be sure to tell him that Gordan Delaney Says Hi. The Tony Guy

Gordy
Looks good Al and it was nice to talk to you at the Nats This year.

Hi Gordy, If Al's Bearcat flys 1/2 as good as your Tony did it will be world class!!! If I did not say it at the Nats let me do so now. Thank you for letting me fly this beautiful airplane of yours! I felt that in one flight that I could have done better with yours than I did with mine! By the way, slave labor does not figure into BOM.
Richard Oliver

Maverick,

Did you mean "Critical Mass"? You already know how the BBQB Bearcat flies.

>Hi Gordy, If Al's Bearcat flys 1/2 as good as your Tony did
>it will be world class!!!

That Tony is kind of a bad mother***(shut your mouth!!!).

I do, however, plan to give Gordy a run for his money someday....

Dr. Jekyll will be done this winter. I am making a few minor changes before we glue him all together.

Mr. Hyde is all refurbed and ready for spot paint. Sans counter balances. I think we have the problems sorted out now. About a few hundred flights on the Shear Panic has revealed the problem, I believe.

Doug and I got a few flights on the BBQB. There was much discussion. Doug had Furias 2 on the CAD right now.

I think GZ is gonna get himself one of them Furias 2's...

Al, thanks for the pictures. I've saved a few of them as a Freeman Spitfire is on my building list. Do you do anything special to seal the lucky box L.E. from oil or fuel proof the interior? Normally the flap horn would be epoxied into the flap, at least that's the way I do mine.

The flap pushrod hasn't any special seal. I do glue the entrance of the horn into the flap and the whole mess is painted over. If I really thought there was much contamination going on I would probably seal the entrance with a piece of tape painted over.

Interesting. I always thought people used two flap horns.

What is on the inside of the lucky box? Is it lined with ply, to allow the wire to slide without sticking, and to keep the balsa from wearing?

I've been having computer problems since I upgraded to a new mother board and processor, but, I'm back now.

OK, There has been a number of favorite wing jigs pictured here. I thought I might define jig features which I think are necessary and offer a bit of comparison between my jig and some of the others pictured here.

First, and most important, I think a wing jig should hold the wing in exact alignment, at minimum, the center and both tips, while the construction and sheeting are completed. Completed, as in front and back, top and bottom, all of the sheeting until the wing is absolutely complete structurally. My jig accomplishes just that. One of the photos above show a completed wing, still in the jig, completely sheeted and still supported at both tips AND the center section. All of the photos above have three jig supports, one at each tip and one in the center. The center support isn't removed until the sheeting is complete. At this point in the wing construction the jig tubes can be removed and the access holes to the jig tubes repaired. If you look carefully, you may be able to detect the repairs to the wing sheeting in the next to last photo.

Second, a jig should be affordable. Mine costs $10 for all of the material except the aluminum jig tubes and they cost about $25 for 12' (two 6' sections). It isn't necessary to spend hundreds of dollars to obtain a competent jig.

Third, a jig should be versatile. My jig allows me to build wings with or without dihedral and to work on the front or back, top or bottom by simply removing a couple of rubber bands and flipping the wing as desired. This considerably eases construction by making the wing comfortably accessible to complete each detail. Jigs which hold the leading and trailing edges tend to focus the building process on constructing the top and the bottom of the wing in sequence as opposed to flipping the wing frequently to complete tasks involving both the top and bottom. For me, leading and trailing edge jigs are obstructions to wing building tasks, particularly sheeting, and to a lesser degree, installation of the control system. I favor jigs which allow the wing to be "flipped" easily and exposes the leading and trailing edges. This allows installation of molded leading edge sheeting, flap hinges and flaps and full length landing gears while in the jig.

Fourth, a wing jig should be exceedingly accurate. This jigs alignment is easily checked by "bore sighting" the jig tubes. It is easily possible to build an accurate wing on a bent or warped jig base as long as the jig tubes are shimmed until the jig tubes show perfect bore sight alignment. Bore sighting jig tubes can easily detect 1/64" misalignment. If the jig tubes are straight, the wing will be straight regardless of the base or whatever the base is sitting on. It would be possible to build a perfectly straight wing with the jig base sitting on a bed as long as the alignment is adjusted with shims each time the wing changes orientation. This example is extreme but makes the point that the only necessary alignment is to the tubes, however that alignment is achieved. This bore sighting capability is the primary reason for using jig tubes instead of rods. Jig bases made of particle board or MDF (medium density fiberboard) are strong and flat, far beyond our jig building needs. These materials are quite strong enough in 3/4" thickness, rigid and flat enough to hold jig tubes in perfect alignment, without shims, while sitting on less than a level surface.

Fifth, the use of jigs which support the wing leading and trailing edges preclude the use of molded leading edges. Molded leading edges have several advantages. They are light, quick and easy to make and install, and eliminate problems with sanding conventional leading edges to a consistent radius. With jigs which feature oversize leading and trailing edges held by jigs, we have a finicky job fitting the leading edge and trailing edge sheeting. This construction also poses a problem of beveling the leading edge sheeting to obtain maximum contact with the jig held leading edge. This joint tends to be weak and is subject to spanwise cracking at those intersections. I have enough trouble with stress cracking without adding 48-54 more places for cracks to appear in service.

Finally, a jig should be capable of holding the completed wing in exact alignment at the center and both tips while a jigged fuselage and its jig are mated to join the wing and fuselage while the components are in exact alignment.

There may be other jigs as capable, but none that I know of able to provide all of these features for $35.

Hi Al, would it be possible for you to post a drawing of some sort that would show how the wing, fuse and tail jigs, all work together? I think a jig is the most important component of the build, but have never used more than a wing jig. I am very interested in your complete jigging process.

Glen,

To provoke a bit of discussion, I planned to submit misc photos of wing construction, fuselage construction, tail construction and precision assembly using wing, fuselage and tail jigs simultaneously to join the wing, fuselage and stab, in perfect alignment. give me a couple of days. This was just the first installment.

Great! Thanks Al. Will hold my breath till you post them....please hurry!

This morning I had the thought that I had missed a major argument for the tube type jig by not including molded leading edges in my comments. To this end I have edited my last night's thoughts instead of adding them here to have greater continuity in the description of my jig.