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Avid C HH wing build 101

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Posted

Help! It's Friday the 13th, under an ice storm warning and I need guidance on my wing build!

First: The center to center measurement of the holes for the wing attachment pins on the fuselage is 27 3/8". The book calls for a outside dimension of 30" on the wing spars (that's where you set you stops on the build horses). With 2 1/2" OD spars, I'm a 1/8" shy, should've measured 27 1/2". The spar openings on the ribs do measure 25" on the inside, which tally to 30". Question: Do I move the blocks in an 1/8" to hit the centers on the fuselage? I'll have to shave off the open end of the ribs to allow for this. The wing tanks do measure 24 3/4-7/8, so they are o.k. What would you do? Am I not seeing something?

Second: I'm supposed to trim the trailing end of the ribs. This is one of the first things I'm to do. The end result of this step is to utilize a trailing edge cable. Doing this would give the appearance of a serrated edge like a ol' Spad. I want a straight trailing edge. I saw in the Wicks catalogue (still waiting on Aircraft Spruce) aluminum trailing edge, but don't know what it really is. Wicks only sells a 10' length so I'd have a splice. I saw efil 01's build on here and he used an aluminum trailing edge (great lookin' plane too!). Question: Where did you guys get the edge? Using the AL edge, did you just leave the trailing edge of the rib square instead of tapering the cap strip. Does anyone have any details; close up pictures, drawings of what you did? I remember seeing a build where they even reinforced a trailing edge by glueing tubing inside the angle. Akflyr?

Third: I have to shave the spar stiffener down about an 1/16". What would be the best way to shave it and keep it true? A planer? Looking at the install, I'm thinkin', what a pain! Make a push stick and shove 'er in. Gotta a better way? Stiffener measures 2 3/8, ID of the spar (.083 wall) 2 5/16". It looks to me like the only thing that holds it in place when installed, is tail end of the rivets holdin the middle of the strut attach bracket. Right?

Fourth: For structural adhesive I've got 3M 2216 Epoxy Adhesive. Sold in'89, it's as hard as a rock. Whadda y'all use? I have non-tautening nitrate dope (CPC Certified Coatings, vintage 1989). That's what the book calls for on all wooden parts. I trialed a piece of plywood with a couple of coats and it's not water repellant. It is powerful stuff and looks o.k. I do have Poly-Fiber epoxy varnish. Is that what I should use? I

I'm gonna stop here for now. The answers to these questions will get me goin'. I sure would appreciate you guys lettin' me know what ya'. Somebody said the only stupid questions are the ones you don't ask! Well.........

Wyatt

 

 

,

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Posted (edited)

If your drilled holes in the spars end up at 27 3/8" C to C, you will only be off 1/16" in each spar if you center the holes between the 2 spars.  Hope that makes sense.   I wonder if your fuselage carry throughs are warped a bit so they ended up narrow.   I don't have a build manual here, are you sure this isn't covered in one of the pages on the wing build.  As far as the aluminum trailing edge goes, you end up with a splice ever 3 feet anyway.  Now way you could ever cut out for the verticle part of the rib, and not cut the top.  Here is a link to the aluminum trailing edges from Aircraft spruce.   http://www.aircraftspruce.com/catalog/mepages/trailedge.php?clickkey=649209   They will cut them for you to 3' 4" in length to say on shipping.  They did for me.  I wouldn't use the old chemicals.  New scottsweld 2216 or Hysol 9460 is the epoxy to use for glueing things like ribs and such.  I like the polyfiber system for covering.  Real easy to work with if you follow the manual.   For the spar stiffener, don't they show clamping the spar to make it egg shaped so you can put the stiffener in without scratching the inside of the spar?  I think that's in the manual.  Might be a good bit harder with the .083" wall thickness spars verses the .065" ones.  Here are a couple of pics of my trailing edges installed.    Home this helps and makes a bit of sense.  JImChuk

PS  make sure to scuff sand the inside of the trailing edges where the glue will stick them to the ribs to get a good bond. 

 

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Edited by 1avidflyer
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Posted (edited)

Nice plumbers clamps - genius! 

He is not far from Wicks, and they will cut to 8' or 6' for UPS shipping, or just go get them.  I buy Hysol 9460 by the quart kit at Kitfox, - easy to mix and use,  but it aint cheap.   Harbor Freight digital scale for $25 to $30 works for me.  Craft sticks (like popcycle sticks) in two sizes at Walmart, and use small plastic cups I saved from yogurt, butter, etc.  Purple Scotch Brite pads to clean spars and aluminum edge before gluing.   Get a bag of cotton flox to mix with 9460 at Wicks - Kitfox only gives you a nickel's worth for the same price.   micro balloons (tiny glass beads) are also mixed with 9460 for the strut fittings glued and riveted to the spars.   EDMO

Edited by EDMO

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Posted (edited)

The small amount 1/16" off of each spar hole center won't pose a problem with flying or folding. Happens all the time due to weld creep I suspect. Do not alter wing specs or rib webs. Attached pics from my A+ so you can see where my front spar holes fell (and a D.I.Y. hole finder idea). Wing tips are perfectly level when folded.

Refer to the Avid Mk-IV build manual in the Files and Forms section to see the proper way and measures to use the metal trailing edge i.e.., do not taper the capstrips. I used PF epoxy varnish on everything except the capstrip faces, leave them bare. Just cover faces with easy release blue or yellow painters tape to keep them clean until covering.

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Edited by dholly
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Posted

Reason I said to have them cut the trailing edge to 3' 4" is you will be cutting them to 3' long any way.  3 X 3' 4" = 10' 0"  JImChuk

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Posted (edited)

Reason I said to have them cut the trailing edge to 3' 4" is you will be cutting them to 3' long any way.  3 X 3' 4" = 10' 0"  JImChuk

Jim,  I think the HH wing ribs are on one foot centers, more or less - He could use a 10 foot piece and a 2 foot + piece for each wing plus enough for the tips if he goes and picks it up - any way you figure, he will need 3 pieces of 10 footers to have enough to do 2 wings.   You can just notch them every 3 feet instead of cutting them.   EDMO

Edited by EDMO

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Posted

Ha, it will be interesting to see ACS shipping cost for the TE material. :)

Jim, squeezing the old .058 and current .065 spars with a wooden clamp is a Kitfox manual trick. The Avid method for .083 spars is just shoving it in with a special push stick. You WILL finish with a hammer... and let me tell you, lining up the rivet pockets is a beotch if your stiffener is tight.

Wyatt, make sure all metal drillings from installing the lift strut brackets are removed to avoid creating any scratches when pushing in the stiffeners!

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Posted

Thanks for gettin back so quick!

Yeah, I really didn't think it be that bad being a 1/16" off on each spar, but it was a descrepency. Got ya' JimChuk. At each of the flaperon hinge point there has to be a splice! Looked at the Aircraft Spruce link and saw the trailing edge. I couldn't tell what it was in the Wicks catalogue. Love the clamps too! I'll have a look at the MkV build and see what they say. No, there ain't anything in the book that saw about clamping and egg shelling the stiffener. I don't understand. Do you mean that I would contour the edges to fit the profile of the ID of the 2 1/2" spar?, I will build the wings to spec, 30" outside to outside of the spars, except with a 1" twist opposed to the 2" called for. Poly-Fiber for me, gotta love that MEK!  Hysol 9460 and digital scale for proportions, got it written down. How do you get it from Kitfox? Gotta get on their website? Dholly, I was wondering how to nail that hole transfer. Another great idea! What did you make it out of? Looks like leather. I saw that you improvised outside the lines on the rear spar cutout template. Start long and trim to fit?

Thanks again guys! Oh and hey! Anybody goin' to Sebring, FL for that expo? I'm headin' down to make a cowl swap and time it to go, 25th to the 28th is what chopndrag said.

G'night

Wyatt

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Posted

Reason I said to have them cut the trailing edge to 3' 4" is you will be cutting them to 3' long any way.  3 X 3' 4" = 10' 0"  JImChuk

Jim,  I think the HH wing ribs are on one foot centers, more or less - He could use a 10 foot piece and a 2 foot + piece for each wing plus enough for the tips if he goes and picks it up - any way you figure, he will need 3 pieces of 10 footers to have enough to do 2 wings.   You can just notch them every 3 feet instead of cutting them.   EDMO

The rib tails are still on 3' centers in both STOL and HH wings, and that is where the trailing edges get cut.  JImChuk

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Posted (edited)

I'll look for a pic in my KF manual that shows their stiffener insert 'squeeze' procedure. Keep in mind though that those stiffeners were extruded aluminum vs. the wood you are using. Like Jim said, dunno if the heavier .083 spars would temporarily distort rather than permanently deform if you tried to do that to your Avid spars.

Yes, you will need to router or round/sand the wood stiffeners to meet the spar i.d. profile. Just to throw another idea at you, several builders have made 'improvements' to the original Avid factory stiffeners over the years. Here's a link to what I did: http://www.avidfoxflyers.com/index.php?/topic/264-mtow-modifications/

The rear spar cutout template showing in my pic was out of the Mk-IV manual but modified for use on my A+. Obviously, it is not final positioned in the photo, still needs to be slid down over the spar hole before marking the cutouts. There were slight differences in the spar cutout profile between Mk-IV and A+ and I wanted to keep as much meat (spar material) as possible, so I also left the cutout line a hair long and did my final cutout profille trimming with a Dremel tool after mounting the wings and test fitting/swinging them.

The hole finder was made from some vinyl siding scrap and other bits and pieces on the bench. ;)

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Edited by dholly
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Posted

Adding one more note to this:  The holes where a rib goes over the strut fittings may have to be enlarged a little - that is if the Avid is like the Kitfox where there is a rib located at the same place as the strut fittings.  EDMO

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Posted

Back here again!

I should've mentioned, my manual calls for 17 3/4 centers on the ribs. I just thought I had 6 extra! Jeez! I've got 18 ribs and 6 half ribs (fuel tanks).....12" centers! I'm guessing this kit was sold at the same time upgrades were being made. I got caught in the transition. Maybe the Mk4 build manual would be the one to follow? Gonna study it. I saw the beefed up version of the stiffener, hell for stout, like it! Oh! (Just had an epiphany!) I see the egg method! You actually squish the spar to an egg shape! There ain't no way you're gonna egg that .083 wall to get that stiffener in. Wicks catalogue doesn't have 2 1/2, .083, I'm hopin' Aircraft Spruce does. I'm gonna get a trial piece and play with it. Yeah, the spar cut out, the way you did it is the way that I will. Don't want to be in a situation where you've cut it twice and it's still too short, a lot easier to cut off than to add on! Hey! How many coats of epoxy varnish do I put on? Tha book calls for 3 coats of the nitrate dope. I've got PF surface cleaner. Good enough for glue prep? If not, what would ya use?

Wyatt

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Posted (edited)

Are you saying that you need 2 1/2" diameter tubes for spars, or just a short test piece?  Good luck on finding any .083 wall....unless someone has a scrap piece from a wrecked wing - .065 yes, you can buy that.  Some of the guys, like TJay, Suberavid, have bought the stronger, 60" long, inserts from Just Aircraft, but they have to be made smaller diameter because they are for .065 Wall spars.  Kitfox sells them too.  I have a set.     EDMO

Edited by EDMO

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Posted

Yeah, I'm gonna try to find a couple of feet of 2 1/2" to work with.

Wyatt

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Posted

I've been trying to find a Mk4 build manual, but no luck. Anyone point me in the right direction?

Wyatt

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Posted

Ha, it will be interesting to see ACS shipping cost for the TE material. :)

Jim, squeezing the old .058 and current .065 spars with a wooden clamp is a Kitfox manual trick. The Avid method for .083 spars is just shoving it in with a special push stick. You WILL finish with a hammer... and let me tell you, lining up the rivet pockets is a beotch if your stiffener is tight.

Wyatt, make sure all metal drillings from installing the lift strut brackets are removed to avoid creating any scratches when pushing in the stiffeners!

Hey Doug,

 

Since you have had your grubby lil dick skinners on both of the ribs, do you think I could make some "overlays" of some sort to change the HH rib to the KF IV profile.  I was thinking some creative work with a little ply to reprofile it and glue them on top and bottom on the ribs then cover.  I really think the Coyote wings would be great if it had the KF airfoil.  I can get a riblet wing kit from D&E but it leaves a lot to be desired and reprofiling my existing ribs would be pretty quick and simple.

:BC:

 

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Posted (edited)

Wyatt,  As far as centers on ribs, what ever you do, make sure they fit the flaperon hangers.  That is the critical part.  I've seen where someone  had a brace stick pushing the rib to the side so it would fit the flaperon hanger.  That did work, but looked poor, although you couldn't see it with the fabric on the wing.  You can see it to, and I had nothing to do with building the wing originally.  :-0   You could even clamp the flaperon onto the rib tails when you go to glue, just so you make sure it's right.  JImChuk

Edited by 1avidflyer
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Posted

Wyatt,  As far as centers on ribs, what ever you do, make sure they fit the flaperon hangers.  That is the critical part.  I've seen where someone  had a brace stick pushing the rib to the side so it would fit the flaperon hanger.  That did work, but looked poor, although you couldn't see it with the fabric on the wing.  You can see it to, and I had nothing to do with building the wing originally.  :-0   You could even clamp the flaperon onto the rib tails when you go to glue, just so you make sure it's right.  JImChuk

When I rebuilt my wings and replaced the rib tails I used measurements on the first wing and ended up having to re-do it. When I bolted up the flaperons they had a slight bend to them and would "camber" / "pop" over center.  That sucked so I pulled the offending rib tails off and did as Jim suggests and clamped the flaperon to the ribs to use for perfect alignment.  Much better and actually faster way to line the ribs up!

:BC:

 

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Posted


I just had another idea.. the ribs are not really that heavy in the grand scheme of things.  It would be easy to "split" the KF ribs down the center and just glue them in next to each existing rib and then anchor the fabric to them while leaving the existing ribs in place for the flaperons to hang off of.  Many ways to skin a cat.

 

:BC:

 

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Posted

Leni, sorry bud. I gave my last KF 4-7 rib to the guy that bought my two KF kits That I sold last year. One kit was missing a skylight brace so I gave him the rib to fabricate one. 

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Posted

Last price I heard about a year ago was $78 a rib from Kitfox.  EDMO

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Posted

If you aren't in a big rush Leni, I could send a sketch when I get home.  2 months though.  JImChuk

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Posted

Guys!!

Holy s**t Batman! This build manual is 10 times better than what I have!! I've done nothing but skim over it, but what I see is Bible! Beg pardon. 

Wyatt

There'll be a pause while I study. Thanks!

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Posted

HI guys!

I'm out at Zepherhills Airport, Fl waitin' on chopndrag to do a cowl swap and thought I'd holler while killin'time. On the Mk4 wing build, it shows an aluminum leading edge. It wasn't included in my kit. On my way back north I'm figurin' on stoppin' at Aircraft Spruce to pick up trailing edge and I was thinkin' about gettin' leading edge too. Measuring the short nose ribs, they are 14 1/4". The leading edge I'm lookin' at is on page 58 of their catalog. Options are 12" and 18". Strange, it says it comes in a roll too. Questions: Does a roll of leading edge sound familiar? Which would I want the 18" or  12"?

Wyatt

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