Wing tank clearance issues

[High Country 69]

I'm ready to install my wingtanks and they stick up aprox 1/8" + - above each rib. I'm not sure how to fix this. any ideas?

-Robert-

[horsepower 24]

I'm ready to install my wingtanks and they stick up aprox 1/8" + - above each rib. I'm not sure how to fix this. any ideas?

-Robert-

Not sure it would be an issue,they seem to change shape alittle when full of fuel,check with the tank manufacturer and see what he says.Randy

[EDMO 1078]

I'm ready to install my wingtanks and they stick up aprox 1/8" + - above each rib. I'm not sure how to fix this. any ideas?

-Robert-

I had the same problem with my tanks - I just used 9460 to glue on another cap strip from front spar to just behind the rear spar on top of the original on each side of the tanks, and then blended the ends with 9460 to match profile.

ED in MO

Edited 21 Oct 2012 by Ed In Missouri

[dholly 718]

Are these the new f/g tanks from Airdale?

[High Country 69]

Are these the new f/g tanks from Airdale?

Yes they are the new F/G tanks with flush fill caps.

Just a bit more info- I'm building a Hybrid HH Speed wing. the first rib and the #4 rib are both the transitional root ribs that Avid originaly used to make room for the 13 gal tanks, the rest are the speed wing rib profile so it tapers down after the 4th rib. My first thought was to add a second strip on top to make them higher than the tank then I could make two thin stirps on top of the tank as well where #2 and #3 ribs would be then it would appear as though there was not even a tank in there and since it tapers down after the tanks anyway it would not look funny to be any "thicker" in this area. Is this a good idea, bad idea, any better Ideas. one of the tanks is pretty good just the other that has this problem? also I have checked and rechecked the wing twist and it is right on

-Robert-

[EDMO 1078]

Yes they are the new F/G tanks with flush fill caps.

Just a bit more info- I'm building a Hybrid HH Speed wing. the first rib and the #4 rib are both the transitional root ribs that Avid originaly used to make room for the 13 gal tanks, the rest are the speed wing rib profile so it tapers down after the 4th rib. My first thought was to add a second strip on top to make them higher than the tank then I could make two thin stirps on top of the tank as well where #2 and #3 ribs would be then it would appear as though there was not even a tank in there and since it tapers down after the tanks anyway it would not look funny to be any "thicker" in this area. Is this a good idea, bad idea, any better Ideas. one of the tanks is pretty good just the other that has this problem? also I have checked and rechecked the wing twist and it is right on

-Robert-

You can do whatever it takes to make you happy - Dont think it will affect the performance or looks.

BUT, I would make both wings the same.

ED in MO

Edited 22 Oct 2012 by Ed In Missouri

[dholly 718]

Robert-

I called Brett on the tanks you bought a while back and found they are made by the same place making the 'new' Ethanol resistant tanks for Kitfox today. After your post here, I wonder if they goofed and the profile is actually for a KF? Is the tank ~1/8" above the capstrip for the entire length of the rib front to back, or just the rear half? Reason I ask is this is what happened when I used Skystar slip-in wing tanks in my Avid Mk-IV HH. The rear spar hole in the KF rib is positioned lower in the web than in the Avid rib, result is Skystar tank sat above the entire length of the top capstrip of standard Avid HH ribs but most pronounced along back half of tank. No prob on the underside.

In your case, easy fix to glue one or two extra lengths of capstrips material onto the rib to raise the capstrip height if necessary. Just be aware that too much height to the rear will cause interference with wing fold clearance so test fit before covering. Dont ask how I know this! Why not sand a side to side root to tip taper on the outboard transitional rib capstrip to help ease the fabric transition down to the adjoining standard speed rib. Yes, also glue some capstrip material right to the tank and glue your fabric to that. Will look much better than gluing fabric directly to the tank top, IMHO. Might consider adding some thin polyfiber batt padding over the tank between those 'false' capstrips to provide a smooth chaffe free tank top surface.

I too am using a second 'transitional' root rib outboard of the wing tanks on my Avid+ project with custom hybrid long spar 'speed hauler' wings. Might even use another between two smaller poly tanks ala the Rocky Mountain tanks for Ridge Runner. I like the big single tank but wonder if I'd be more comfortable with E-proof poly and an extra rib for greater wing strength. BTW, these special transitional ribs were used on Avids with speed or aerobat wings so an owner could interchange to STOL or Heavy Hauler wings and have the wing roots meet up to the standard butt rib (same for all wing options), not sure it had anything to do with the old Avid 'glassed in' wing tanks. At least, that's what my build manual said IIRC.

Edited 22 Oct 2012 by dholly

[High Country 69]

Thanks for the reply's,

Doug- I had considered these may have been the KF tanks they seem to fit pretty good other than being to high though, and its mostly just on the one tank. I did find this- http://www.wingsforum.com/viewtopic.php?f=218&t=20563 I'm wondering if I can just trim them down a bit to set in lower then still use thin wood strips if necessary. Seems if I do add the wood strips I will have to raise up my butt ribs too hope this doesn't interfere with the skylight fitting, If so I guess I will replace it now with the smoke lexan rather than later. What would be the best wood to use if I wind up going this route. prefer something I can get local like Home Depot or Lowes.

-Robert-

[dholly 718]

I put a few pics of my prob fitting Skystar tanks in my Avid Mk-IV. If that is similar to your issue, I don't see how camfering the front or rear tank edge (like the tank install on the Just forums) will allow the tank to set lower below the ribs. The coves are molded in, can't change that. I still wonder why one tank was ok, the other not? Does the 'bad' tank wobble more on the spars than the good one? Ie. the KF tank should have 1/2" twist built in, the Avid 1-1/2", so the KF tank will not set on both Avid spars without quite a bit of wobble due to the different twist specs.

I remember thinking it seemed like a lot at the time I fit mine. If the coves don't follow along and fit flat on your spars I would question it. If it does, and the tanks sets above the capstrips on adjacent ribs, I guess it is a personal judgement call whether to build up the capstrips or see if Brett has/can get you another to try. Yes, if you build up the transitional rib capstrips, you will need to raise the butt rib capstrips too, or reposition the butt rib on the standoffs to match.

I believe both Avid and KF used Aviation grade Mahogany ply w/90*degree ply layup for rib webs, and either Aviation grade Spruce or Birch 5-ply for cap strip material. If you opt out of the mail order Aviation grade cap strip material, seek out Grade 1 or AA Marine birch ply as it will have 90*degree ply orientation, higher quality sanded face veneer, no core voids and a fully waterproof structural adhesive. Birch is also stronger than mahogany or spruce, but dunno if you can get that in the thickness you need at the big box stores. I used a 1/8" Marine grade birch 5-ply for my floorboards sourced from a local specialty lumber yard, it would probably work fine as cap strip material too.

[EDMO 1078]

Thanks for the reply's,

Doug- I had considered these may have been the KF tanks they seem to fit pretty good other than being to high though, and its mostly just on the one tank. I did find this- http://www.wingsforum.com/viewtopic.php?f=218&t=20563 I'm wondering if I can just trim them down a bit to set in lower then still use thin wood strips if necessary. Seems if I do add the wood strips I will have to raise up my butt ribs too hope this doesn't interfere with the skylight fitting, If so I guess I will replace it now with the smoke lexan rather than later. What would be the best wood to use if I wind up going this route. prefer something I can get local like Home Depot or Lowes.

-Robert-

Since the added material over the original capstrips is not "structural" and only to ensure that the fabric clears the tank, I think the plain wood strips that Spruce sells would be fine. I had some veneer plywood left over from my kitchen, so I cut some one inch strips from that and used it. Anything cheap and easy should work - as long as glue will stick the fabric to it. Blend it into the original at front and behind the rear spar so you do not change the trailing edge.

ED in MO

Edited 23 Oct 2012 by Ed In Missouri

[6320012s 12]

Since the added material over the original capstrips is not "structural" and only to ensure that the fabric clears the tank, I think the plain wood strips that Spruce sells would be fine. I had some veneer plywood left over from my kitchen, so I cut some one inch strips from that and used it. Anything cheap and easy should work - as long as glue will stick the fabric to it. Blend it into the original at front and behind the rear spar so you do not change the trailing edge.

ED in MO

Anybody considered replacing the plywood with .040 aluminum? I have a wing tank that appears to have sprung a leak somewhere on the top, and I would like to manufacture a cover plate that will allow access to the tank for future repairs if necessary. Anybody see any reason why such a cover could not be screwed or riveted to the rib cap strips? I am thinking I will leave enough plywood at the leading edge to fasten the aluminum to and then use a couple strips of the plywood cut-out to stiffen the aluminum. Any ideas?

[EDMO 1078]

Anybody considered replacing the plywood with .040 aluminum? I have a wing tank that appears to have sprung a leak somewhere on the top, and I would like to manufacture a cover plate that will allow access to the tank for future repairs if necessary. Anybody see any reason why such a cover could not be screwed or riveted to the rib cap strips? I am thinking I will leave enough plywood at the leading edge to fasten the aluminum to and then use a couple strips of the plywood cut-out to stiffen the aluminum. Any ideas?

This has been done on some factory-built planes - I think the aluminum could be lighter, maybe .030 or .025.

My favorite attachment would be aluminum riv-nuts, with a washer or aluminum strip under the capstrip.

Havent had much time to think about this - Just figured on cutting fabric and repairing if need be, but mine is not covered with plywood.

But since you have to cut yours anyway, this might be the time for a modification that could help you in the future.

I would like to hear others thoughts on this - for or against, and why.

ED in MO

Edited 23 Oct 2012 by Ed In Missouri

[High Country 69]

These tanks seem to fit the twist perfectly they sit real nice on the spars just seem to be a bit to high, I guess they thought I needed that tad bit more fuel anyways, I picked up some nice plywood from a fancy woodworking cabinet shop today and will just raise them up to match the tanks, I don't think I can go above the tanks to make it look like they are not even in there as these are the new flush fill tanks ie: no fill neck sticking up so I have to stay flush with them. shouldn't be a problem also it gives me the opportunity to raise the butt ribs and gain a little more head room. I'm thinking Gorilla glue should work fine to attach the new strips any thoughts of this?

[EDMO 1078]

These tanks seem to fit the twist perfectly they sit real nice on the spars just seem to be a bit to high, I guess they thought I needed that tad bit more fuel anyways, I picked up some nice plywood from a fancy woodworking cabinet shop today and will just raise them up to match the tanks, I don't think I can go above the tanks to make it look like they are not even in there as these are the new flush fill tanks ie: no fill neck sticking up so I have to stay flush with them. shouldn't be a problem also it gives me the opportunity to raise the butt ribs and gain a little more head room. I'm thinking Gorilla glue should work fine to attach the new strips any thoughts of this?

If you are out of 9460, I would at least go with some kind of epoxy - not familiar with G glue. T-88 is good.

But, for blending the ends, 9460 with some flox is best, IMO.

EDin MO

Edited 24 Oct 2012 by Ed In Missouri

[akflyer 1427]

These tanks seem to fit the twist perfectly they sit real nice on the spars just seem to be a bit to high, I guess they thought I needed that tad bit more fuel anyways, I picked up some nice plywood from a fancy woodworking cabinet shop today and will just raise them up to match the tanks, I don't think I can go above the tanks to make it look like they are not even in there as these are the new flush fill tanks ie: no fill neck sticking up so I have to stay flush with them. shouldn't be a problem also it gives me the opportunity to raise the butt ribs and gain a little more head room. I'm thinking Gorilla glue should work fine to attach the new strips any thoughts of this?

I did multiple tests when I had to replace the rib tails on mine. Hysol. T-88, wood glue, 30 minute hobby epoxy and gorilla glue. The gorilla glue won hands down. I used the gorilla glut to put the new rib tails and cap strips on my plane. 3 yrs and 300 hrs later they are holding up just fine.

What you are talking about doing to build up the rib profile is in no way structural, only cosmetic. You could super glue the second cap strip on and be fine.

[High Country 69]

I did multiple tests when I had to replace the rib tails on mine. Hysol. T-88, wood glue, 30 minute hobby epoxy and gorilla glue. The gorilla glue won hands down. I used the gorilla glut to put the new rib tails and cap strips on my plane. 3 yrs and 300 hrs later they are holding up just fine.

Thanks for the tip leni, I always knew that stuff was like liquid duct tape.

[High Country 69]

Good news after a ton of sanding i don't have to buildup the cap strips after all. Now that I finally had the time to sit down and really look at things i decided that the ugly lip on the bottom side of the fore and aft edges of the tank were just "left overs" from the mfg process and not part of the design, so i sanded them down and ta da it fits nicely just a bit of irregularity compared to the ribs but i can't complain this is the best its gonna get. I also rounded all the edges so the slight offset from the ribs will have a nice transition. should look just fine. as a side note I really like the new flush fill caps.

-Robert-

[Trackwelder 12]

I used the wing tanks, and they did not seem to be a problem until I put the covering on, then they showed, I used early designed wings without the leading edge and am hoping that when I add fuel, they will settle down and not be obvious, they don't actually stick up but stand out.

[Bandit 286]

This is how I finished the top of my wing.

[SkyPirate 8]

Nice job Bandit...