Composite Leading Edge

[desertfox1]

I have some pictures of Bill Prokes installing LLE on a SS wing.
The PVC guide blocks had been bonded on. The new parts
come in two pieces, joined on number 5 rib. It took about 2
hours to fit, trim and Hysol the wing. The trim saw Bill used
was almost magic. Fast, very little glass dust. Sure looks
good after covering.

Desert Fox 1

[SSFoxBuilder]

Does anybody know why the composite "Laker" leading edge wasn't designed to completely cover the top false ribs? Was this for aerodynamic or aesthetic purposes? Weight savings, possibly?

[desertfox1]

The airfoil designer, Harry Riblett, asked for at least 6" from
the leading edge. We met the requirement for aerodynamic
purposes and stretched just a little for appearance. Weight
is allways a consideration.

Phil

[SSFoxBuilder]

Noted. Thanks for the insight!

[avidflyer]

Does this system extend out past the front spar, and if so how much. I know that the Kitfox 4 used a plastic piece glued to the front spar to extend and streamline it, does this fiberglass piece take the place of that plastic extention? Both of the Avid Flyer MK IVs I've owned used a sheet of aluminum which was glued to the spar and covered the falseribs. It didn't extend the front spar forward however. Thanks, Jim Chuk

[jiott]

Yes it does use small pieces of the plastic extrusion placed at intervals along the front spar to make the fiberglass leading edge conform to the shape and spacing of the original full length extrusion.

Jim

[jrevens]

I notice that Bill has used clecos to hold it down after application of the Hysol. Do you remove them before full cure, or coat them with something to avoid sticking & allow removal after cure, or are rivets installed (& if so, what type)? Could you clarify the procedure... I'll be doing it fairly soon. Also, exactly what saw did you use for trimming & scalloping the fiberglass? Could you describe that process? Are the 2 sections overlapped or butted at the #5 ribs?

Sorry for so many questions at once!

[HighWing]

Clecos are used extensively during construction of the Lancair. Top and bottom fuselage sections are like long canoe shapes that are Hysoled to gether with clecos every few inches. Wing skins, stabilizer halves - everythinhg. We never coated them with anything and we cleaned them up when necessary with the cleco held in the pliers against a wire brush on one end of a bench grinder.
Lowell

[desertfox1]

Right Lowell, most don't need cleaning. We cleco the parts on before
trimmimg to mark the ribs and false ribs with a sharpie. Then using a
simple pattern the scallops were drawn. Using an inexpensive saw
from Harbor Freight they were trimmed, hysol applied and clecoed
untill cured. When using a saw like ths the fiberglas needs to be
supported with a 2x4, cuts clean and with little dust.

Phil

[jrevens]

Thanks, Phil & Lowell! That's what I needed to know. Having built an all-metal airplane, I've used clecos a lot, but not with epoxy. In the areas that they have been necessary on the Kitfox project, I have been pulling them & cleaning in alcohol after installing rivets & before the epoxy set. Thanks for the tip about the saw!

[HighWing]

Another idea on the cutting, the Lancair guys used diamond discs for their dremel tools. Also available at Harbor freight. Then a possible touch up with a sanding drum.
Lowell

[jrevens]

How are people handling rib-lacing with the Laker leading edge? Are you starting the lacing where the fiberglass ends? Since the fabric will be glued to that large surface area on the top, would lacing still be desired over the Laker leading edge (by drilling holes in the fiberglass)? My guess is that it might negate some of the aerodynamic improvement by doing that... true? If starting the lacing after the fiberglass, would you still lace the bottom all the way forward, catching only the bottom section of the rib in that area? Thanks in advance for any comments.

[HighWing]

John,
I don't think lacing would be necessary. It would be similar to how the fabric is handled on the top of the fuel tank. That said, though, I put aluminum on top of the leading edge essentially a poor man's LLE. I just used the two coats of Polybrush on the leading edge, then shrunk the fabric and applied the fill coat of Polybrush over the wing. I did pick up the lacing about two inches behind the aluminum skin.

[Av8r3400]

Lowell - Are you getting any oil-canning from the flexing of the wing with this setup?

[HighWing]

Lowell - Are you getting any oil-canning from the flexing of the wing with this setup?

Larry,
I guess the short answer is - I don't know. When we were thinking of this, I remembered Hal who at the time flew an early Rans S-7. He would often get oil canning while on the ground. When it was pointed out to him, he would grab the wing tip and with a big grin, shake the tip and the wing would pop straight.

I decided I needed it straight on the ground to void people pointing out my crooked wing. When building, I supported the wing at the root end and at the lift strut brackets so it would be in it's typical unloaded ground geometry and hopefully lie straight when people could see it. I riveted a "Z" channel at the trailing edge of the aluminum as a stiffener there and the Z loosely captures the stringer that would normally support the aft ends of the false ribs (I eliminated the false ribs entirely to help compensate for the weight of the aluminum). The one thing I overlooked in my planning was the weight of full tanks while on the ground. On rare occasions, the bay immediately outboard of the right wing tank will show a slight depression near the trailing edge of the aluminum, but not consistently and it is only visible from the vantage point of a ladder.

The "I don't know" part of the answer really refers to what it looks like in the air when it tries to flex and assume other than the at rest geometry. With that in mind, though, it does seem to fly better - but that might be akin to how much better a car feels after washing it. One definite and measurable improvement is full power stalls - much more stable, not the violent wing drop I used to get with my first Model IV. Sorry for the quality of the attached image, but it shows the general appearance while on the ground.

[jamesmil]

would like to post my 2ct, worth on the instalation of the laker leading edge.
we used avation snips to do all the cutting as the fiberglass is very thin and we just made a stright cut top and bottom with no scallop. also we started the rib stiching after the l/e.
to lay out a stright line we slid the l/e on the wing then got a mark at each end and used masking tape to lay the line stright, if you use this method to get your stright line make sure to mark the tape with arrows to show which side to cut. :mad: no i didn't do it this time but it is very expensive to learn the hard way.:eek:

[Esser]

Are the scallops just for aesthetic purposes?

[mr bill]

I did not scallop my leading edges and there is not a pronounced "edge" under the fabric. Using the Stewart System adhesive was new to me, but I liked it being water based, very strong bond and easy to get off your fingers.

[jrevens]

I see that there is a water-soluble transparent coating of some sort on my Laker leading edges. It's kind of a mess getting it off. It's very thin, and some of it stripped off when removing the tape used for shipping. Anybody else notice this?

[AirFox]

Your suppossed to use soap and water to wash it off. The film just disolves.

Scott

[jrevens]

Thanks, Scott! I guess I'm pretty stupid about fiberglass stuff.

[AirFox]

I had to ask the question too.

Scott

[Esser]

With the LLE do you no longer require the extrusions on the front spar? I can't find them any where and I am wondering if i will even need them now.

[mr bill]

The extrusions act as a spacer from the front spar, when installing the LLE. The template for locating them is in the build manual. I used three inch long pieces in the approximate location of each rib. They are sold by Kitfox Aircraft. I have a bunch left over that I can send.

[Esser]

Thanks Mr. Bill. I will look for these small piece this weekend and if I can't find them I will send you a PM. Thanks again!

[AirFox]

Esser,

My extrusion pieces were shipped in the LLE kit. In the middle of the plastic wrap.

Scott

[jrevens]

The instructions that I got called out 5 pieces, each 1.5" long, to be installed at the #1,3,5,7 & 10 ribs. Is that still the recommendation? Thanks, Phil or Bill.

You cut them out of a longer piece that came with the leading edges.

[Esser]

In the LLE instructions, it says cut 10 pieces 1.5 inch and line them up with the inboard edge of rib one. But in the pictures in step 2 on the far right side, it shows about a 4" long piece but up to the end of the spar. Any hints on which way is correct?

[jrevens]

For whatever it's worth, Esser, I don't think it's very critical. You could make your pieces longer, or not. I made the ones in the middle, at the joint between the 2 LLE pieces, twice as long (approx. 3"). They're there mostly to just key the alignment & position of the LLE.

[desertfox1]

You are right John, the PVC pieces are simply for alignment. If
One is a little longer I would use it at where they join.

Phil