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Avid C HH wing build 101

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Posted (edited)

Wyatt - A leading edge is not necessary, IMHO. There are many flying fine without it, just requires two false (nose) ribs between main ribs to minimize fabric bowing and retain airfoil shape. If you are dead set on adding leading edge material to smooth the airfoil, I recommend using ply vs. aluminum. Search here for "plywood leading edge" and you will find discussion of why that may be superior to the aluminum leading edge, plus pics of other members wing builds.

Edited by dholly

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The leading edge being mentioned on an Avid wing is really a  piece of aluminum glued to the top, front 16" or so of the ribs.  That's why it would come in a roll.  This picture shows it in place.  JImChuk

 

Photo0036.jpg

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Posted (edited)

Wyatt - A leading edge is not necessary, IMHO. There are many flying fine without it, just requires two false (nose) ribs between main ribs to minimize fabric bowing and retain airfoil shape. If you are dead set on adding leading edge material to smooth the airfoil, I recommend using ply vs. aluminum. Search here for "plywood leading edge" and you will find discussion of why that may be superior to the aluminum leading edge, plus pics of other members wing builds.

I don't know what thickness of aluminum Avid used for the leading edge cover, but I used 1mm Finland Birch plywood, and another builder used .8mm - plywood don't dent like aluminum, and I think the glue joint may be stronger.  I only covered mine because I wanted to extend the leading edge about 4" because of my Subaru engine weight.  I agree with Doug, that there are plenty of Avids and Kitfoxes flying just fine with only a fabric covering the leading edges, and any other type of covering adds weight to your plane.  EdMO

Edited by EDMO

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Posted

Howdy guys,

We made it back from Florida with chopndrag's old cowl and stopped at Aircraft Spruce. I did decide to go with a .8mm birch leading edge. I like the added strength. It came in 2'x4' sheets. There will be butt splices, but I don't think that'll be an issue. We also picked up aluminum trailing edge. Before I left, I placed an order at Wicks. I had ordered cotton flox, micro balloons and Hysol 9460. They said 9460 was in the computer and could get it. I didn't get the 9460 when the order came, so I'll call 'em tomorrow. Both Wicks and Aircraft Spruce carried 9430. Micro balloons and epoxy on the strut attachments and cotten flox mix on the ribs? Never even heard of either one. Is Hysol 9460 the best adhesive?

Tomorrow, I'm gonna start whittling ribs. On the long ribs, it looks like you just cut the cap strip off starting at 12 1/2" from the back of the rear spar cut out, leaving the flaperon attachment. The 12 1/2" measurement is a cut-long, final cut is a string line approximately 12 1/8". The short ribs will trim down to knife point at 12 1/2". Sound about right? For insurance purposes and frame of mind, can you still get undercambered ribs? Yeah, I'm a little gunny. I'll send pictures.

Wyatt

P.S. Undercambered rib mods?

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Posted (edited)

Wyatt,  To reinforce the butt joints on the plywood, cut some 1" or 2" wide strips of the .8mm the correct length and use brown Gorilla glue, or 9460 and clamps to put them inside the butt joints after you put the plywood on the wings.  That really ties the plywood together.   EDMO

Edited by EDMO

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IMG_0179.thumb.JPG.dc68ea345d7ec81be15c4, We used .8mm plywood and did it in three pieces with each seam aligning with a rib. The wood glue we used worked well and created a solid structure. We used superfil to feather the seams and to the spar. I've attached a picture - hope this helps.

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Posted (edited)

IMG_0179.thumb.JPG.dc68ea345d7ec81be15c4, We used .8mm plywood and did it in three pieces with each seam aligning with a rib. The wood glue we used worked well and created a solid structure. We used superfil to feather the seams and to the spar. I've attached a picture - hope this helps.

Gorilla glue is available at Walmart or lots of places, and it is very strong.  I never thought about the HH wing having ribs on 1 foot  centers - it don't work so well on the kitfox with ribs on 18" centers - the 4 foot plywood joints aren't over a rib.   I couldn't pull up the picture ??? EDMO

Edited by EDMO

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IMG_0179.thumb.JPG.dc68ea345d7ec81be15c4, We used .8mm plywood and did it in three pieces with each seam aligning with a rib. The wood glue we used worked well and created a solid structure. We used superfil to feather the seams and to the spar. I've attached a picture - hope this helps.

Hey Rob, I couldn't get that picture to come up. If you would, could ya' try'er again. It could just be me, I'm learning this computer stuff as I go!

Wyatt

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Posted

Once again . . .

IMG_0179.thumb.JPG.f30028260e4267f60f92d

 

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Posted

Thanks Rob!

Heck, I thought you would wrap the front spar! How wide is it? Those intermediate ribs (the ones from the stringer to the front spar) are 14 1/4". 

Wyatt

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Posted (edited)

Thanks Rob!

Heck, I thought you would wrap the front spar! How wide is it? Those intermediate ribs (the ones from the stringer to the front spar) are 14 1/4". 

Wyatt

Wyatt,  If you have a belt sander, or any kind of sander, bevel the front bottom edge of the plywood and it makes a smoother joint to the spar - you could even do that with a block and hand sand the thin plywood edge.   You just want to be about even with the rib fronts.   EDMO

Edited by EDMO

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Posted (edited)

Wyatt - as I remember, around 14 1/2" was the width of our plywood. We used Hysol to secure the plywood to the spar and Titebond 3 for gluing it to the ribs/false-ribs. No wrapping of the plywood and it took only a small amount of superfil to feather it to the spar.

Edited by RobS

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Posted

Sounds like a plan! Love the way turned out! 14 1/2" makes it about even with those short intermediate ribs.

Thanks, got the picture in my photo library! This iPad can be handier than a pocket on a shirt sometimes!

Wyatt

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Posted (edited)

I smoothed my first set in with light weight Bondo, and after that Akflyer told me I should have used Kitty Hair (??) from the auto store - He says it don't crack.  Second set was just sanded to blend smooth.   EDMO

Edited by EDMO

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Posted

Wicks did a little moonwalking on me, they can'get Hysol 9460. They can get Scotchweld 2216 by the quart, special order. Special order makes me think that this is gonna hurt! I gave 'em the green light.

I should've asked because I'm not 100% positive: Do I remove the sliver of cap strip at the tail end of the rib which the flaperon attaches? It does appear that I do, leaving the rib web carrythrough for the flaperon attachment. My pictures in the manual and the drawing leave me a little uncertain.

Wyatt

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Wicks did a little moonwalking on me, they can'get Hysol 9460. They can get Scotchweld 2216 by the quart, special order. Special order makes me think that this is gonna hurt! I gave 'em the green light.

I should've asked because I'm not 100% positive: Do I remove the sliver of cap strip at the tail end of the rib which the flaperon attaches? It does appear that I do, leaving the rib web carrythrough for the flaperon attachment. My pictures in the manual and the drawing leave me a little uncertain.

Wyatt

Wyatt,  I have seen it done both ways - don't think it matters much.  EDMO

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Posted

I think you remove it then where your trailing edge sits on the cap strip you need to file the wood down so the trailing edge is flush with the top of the cap strip, hope that makes sense, If you take pictures of what your doing then ask questions you will get a lot more answers, Terrible hard to describe things with words, at least for me it is,

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Didn't get any whittlin' done on the ribs like I had figured. I was gonna reinstall the landing gear on the fuselage, which I have here at the house. Wanna be able to move it around if I want to. I had taken the wheels and brakes off the mains to get 'em powder coated. That was one thing the original owner had assembled. I knew something wasn't right when I took the stuff apart. So I took the manual out for the reassembly. Yip, he'd mounted the brake calipers forward instead of aft. His holes aren't symmetrical at all too. A littler wallerin' on the holes and grindin' on the flange, and I'll get 'em where they're supposed to be. Put it back to rights. When I get this done, I'll be gettin' back to the wings.

Doggone Wicks never got back to me on the Scotchweld 2216 either. They were supposed to call me back on price and delivery. Wasn't very nice. If I don't hear from 'em I'll get the Hysol off that outfit on the Internet. Thanks!

Wyatt

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Wyatt,  I would get the 9460 - It mixes easier, and I think it glues better than the 2216.   Here is a page from the Kitfox 1 manual that may better explain what TJay was trying to tell you about cutting and filing the capstrips to make the aluminum trailing edge fit flush.  EDMO

Scan0380.jpg

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Posted

EDMO, you're the man! I ain't near the dummy I thought I was! If Kifox put out that detail, it tells me it wasn't crystal clear. I understand, but still will cut one down and post it.

Thanks,

Wyatt

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Posted

The Avid ribs are different from the Kitfox ribs at the tail end.  On the Avid the cap strips go all the way back to a point and meet.  Here is an Avid rib.  JImChuk

 

Photo0011.jpg

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Posted (edited)

Howdy boys! 

I've got some things goin' that don't add up. My kit came with 18 full size ribs, 6 trailing edge ribs, left and right root ribs and 2 wing tanks. The manual says I should have 4 trailing edge ribs for each tank. It said to refer to photo R-1 in section VIII, but I couldn't find the picture. Maybe I'm 2 short? Now looking at the fuel tanks, there are 3 cutouts to accept just 3 ribs on 17 3/4" centers (that's the c-c measurement for Model C). I have fabricated 10 long ribs for flaperon attach points, but know I don't need the all. I haven't touched the other 8. Short ribs should be a piece of cake. No problem to cut them down to make the nessecary short ribs. I took 2 trailing edge ribs and trimmed them for atttachment points, haven't touched the other 4. I figure at least 2 of them have to be attach points. All trimmin' I've done is cut long, 12 1/2" from the rear spar. The book says 12" +/- is the final fit (string line). Another problem I've noticed is the intersection point of the top and bottom cap strips from the spar cut out are about a 3/8" different on the trailing edge ribs and the full sized. The point is longer on the trailing edge ribs. 

I've been trying to decide what to with the brakes the original owner had assembled forward on the landing gear. He mounted them square with the forward gear support. It would work there, but I guess I'll bite the bullet and drill 4 more holes in the brake backing plate to reorient it 45 degrees aft, like the book says. Got to be some sort of logic there. 

Doin' a lot of thinkin' and not much buildin'! Help!

Wyatt

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Edited by 3CW
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Posted

Sounds like you have the correct number of ribs to construct Avid STOL wings, not Heavy Hauler wings (C model kits could have come with either, see links below).

As to the trailing edge rib indentations on your wing tanks, they would be correct for the STOL wing. Later tanks from Avid and [old] Airdale actually had provisions for both rib spacing requirements, you can kind of see them on the pic of wing tanks delivered with my A+ kit.

Would be unusual if the trailing edge did not fall at the same point on the long (flaperon hinge), short and trailing edge ribs unless there was a manufacturing error. I assume they were cut in bulk and assembled with benefit of a jig. If yours are indeed different for some reason, would seem better to be too long rather than too short. Perhaps a bit of Dremel work with a sanding drum to relocate the spar hole further aft in the trailing edge rib web is a possible solution?

To see a detailed description of the (4) Avid Flyer wings, go HERE

To see a detailed description of the Avid Flyer models, go HERE

CIMG6613_0001.JPG

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Posted

Hey Doug,

With the exception of 2 trailing edge ribs and the lack of the correct number of indentations in the wing tanks, I'm thinkin' I got a HH wing build. I've got 144" .083 spars, 7/8" dia struts, undercambered ribs, 6 long 1/2" W-2 drag tubes, 2 5/16" W-3 tubes tubes, 2 1/2" W-4 short tubes. As I see it, looking at your wing tank picture, do I see 5 indentations? That would would be for 4 trailing edge ribs on 12" centers and puttying in the center for HH (that's what the book says to do). Having a total of 18 ribs (9 per wing), that would jive with a 12" centers outbound of the tanks: Heavy Hauler. I don't like the thought of puttin' just 3 trailing edge ribs aft of the tanks on 17 3/4" centers and then having full sized ribs outbound on 12" centers. Whadda' think? Wider centers-STOL wing (I'll have 6 ribs left over)? Or make a couple of trailing edge ribs (or buy?) and butt 'em to the tanks? I see the mission of my plane as one of being able to carry more weight than STOL performance. Heck, I got 2 wing tanks!

Mk-IV HH: .083" thick 2-1/2" o.d. spars; 144" spar length; 7/8" dia. lift struts; Avid undercamber airfoil; (13) ribs ~ 12" o.c.; (1) 1/2" dia. W-2A steel drag tube; (3) 1/2" dia. W-2 alum drag tubes; (3) W-3S Short 5/16" dia. alum root rib brace tubes; (1) W-4 Short 1/2" dia. alum root rib brace tube; (1) W-3L Long 5/16" dia. alum tip rib brace tube*; NOTE: Wing tank replaces (1) W-2A, (3) W-3S and (1) W-4 alum rib brace tubes at the root end of wing; Key rib dimensions (long rib flaperon hinge) are 35-1/2", 71", 106-1/2" and 142" o.c. from tip rib

Lemme know what'cha think! 

Wyatt

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