need advice

[jacques]

Last sunday, I did some flight with a good friend and is helicopter and it took some pictures. I noticed that my fabric on both tanks is strange....

What do you think? (and what do I have to do?)

sorry for the size of the pictures, it is to be more accurate

http://prem1.hiboox.com/images/3712/e4785b85fd74787b7cdf1151707bb937.jpg (http://www.hiboox.fr/go/images/divers/01,e4785b85fd74787b7cdf1151707bb937.jpg.html)

http://prem1.hiboox.com/images/3712/35df48734f937e5d2037003a9569f253.jpg (http://www.hiboox.fr/go/images/divers/00,35df48734f937e5d2037003a9569f253.jpg.html)

[jtpitkin06]

Jacques,

It appears the fabric did not get enough heat to shrink it tight.
It is loose over the tanks and the entire wing.
Compare your wing in flight to other Kitfox photos in flight.
You will notice the fabric should not balloon upward between
the ribs like yours is doing.

The loose fabric on your wing is a concern. Short of recovering
the wing I’m not sure how to shrink the fabric tight without
destroying your finish because heat will melt the coatings.

If you just want to attach the fabric to the tanks you can use MEK
to dissolve the coatings. Then use Polybrush thinned 50/50 to
reattach the fabric. Next, do the usual UV protection with
Polyspray and finally the color coat.

John Pitkin
Greenville, Texas

[jdmcbean]

Jacques,
This can be a serious flight safety issue. If you have a higher res pic please send it to me at john@kitfoxaircraft.com

If you have nay other pics please forward them as well.

Is the wing rib laced ?

[jacques]

Thanks all for your answer. I will wait for John (kitfox) advice.

I will also think about a new fabric on the wings or any other good solution.

[MotReklaw]

This picture give me reason to ask this question....

If fabric is shrunk in 90 plus temps, will it tend to be loose in cold weather?

[Av8r3400]

No. Once the fabric takes a set it will not "stretch" or "relax" back out with temperature.

[HighWing]

One additional comment. Over the wing tank while shrinking, the fiberglass can act as a heat sink and the temps absorbed by the fabric can be less than the temps felt by the free standng fabric. If the fabric is bonded to the tanks completely it is not an issue, but typically the tanks are not in the exact lalinement with the ribs and there will be areas that are not attached. That is part of the issue with Jacques wing fabric appearance.
Lowell

[cap01]

Jacques , noticed that you were resolving the loose fabric from another of your posts . Just curious what you were doing to remedy the condition ?

[jacques]

I have talked with the fabric specialist and he told me that the fabric
on the wing is very nice. In the tank aera also but it seems that the
glue on the tank is not doing its job on the fabric.

The leading edge on this parts is ok as on the root rib and the first rib after the tank. It is also well glued on the leading edge.

The problem is that the ttop of the tank is just below the top of ribs, so when the fabric is glued on the tank there is a small area close to both ribs were fabric do not contact with the tank.

He told me that I can still flying. Also, he told me that I have one day
to do something.

For exemple, if I change my tanks for ethanol able one's , just to
cut the fabric betwen the root rib and the first rib and put new one.

[cap01]

When I replace the tanks in my model IV that's what I did only two ribs further out . Since I was installing the larger tank, one rib was removed and the brace had to be relocated to the next bay outboard . Lowell is correct , the fabric is difficult to shrink correctly over the tank since the tank sucks the heat from the iron . Good luck with your fix

[MotReklaw]

Not trying to cause problems but the instructions for my SS say to NOT attach the fabric to the tank, rather attach it to rib 1 and 3 and the partial rib 2. That's what I'm doing.... Since I am a newby with fabric, I think I'll just follow the manufacturers advice.

Since I am at this stage right now, I did go back and recalibrate my iron and very slowly ironed that area over the tanks and the rest of the fabric at usual speed.

Maybe things were different with some of the older models?

[Dave S]

Tommy,

There is "attaching" and there is "attaching".....which may be two different things.....

I think what the instructions are getting at is not to glue the fabric to the tank tops with poly-tak. The fabric is poly-tacked to the ribs, etc. but not to the tank top.

If I recall, the fuel tanks were thoroughly coated on the top with a generous layer of poly brush which is left to dry....the fabric is then glued down with poly tak on the ribs, edges and ends, shrunk, then when sufficiently generous poly brush is applied on the shrunk fabric over the tanks and worked in with a brush, it will soak through and re-dissolve the first coat of previously dried polybrush and the tank top, fabric and polybrush essentially become one....I'd say they become "attached" as a result of that operation......but not with the poly-tak.

If the first coat of poly brush is not applied to the tank top; or, if insufficient poly brush is applied so it does not soak through to re-dissolve the base layer previously applied to the tank tops, the fabric can separate from the tank top due to lift on the wing.:eek: Also, I'd like to believe that rib lacing is done on the tail of the center rib behind the tank.

I'd check both the SS manual and the Poly Fiber manual carefully. It's not a matter of inconsistency:confused:, its a matter of what is meant by "attach".



Dave S

[cap01]

The book for my model IV also says not to attach the fabric to the tank . But I'm sure to some degree it will get stuck with some of the poly brush passing thru the fabric? If poly brush was put on the tank before the fabric was shrunk I don't see how a person would ever get the fabric to shrink . Seems the heat would soften the poly brush and stick to the fabric before it could shrink

[Dorsal]

I did as Dave S describes and it and it has worked well. Heat shrinking the fabric over the tank also bonded it to the coats of poly brush on the tank. The next coat of PB on the fabric seals the deal. (seemed to shrink just fine)

[MotReklaw]

I'm using the Stewart's System so I substituted EchoFill for the PolyBrush. I used EchoBond in place of PolyTak. Same procedure, different product. Now I'm wondering....

What got me started was the picture of Jacques' wing at the tanks...

[jiott]

I rib-laced the number 3 rib for extra insurance. If you follow the SS7 manual and fill the gap between the tank edge and rib #3 capstrip with Hysol you wont be able to rib lace #3. Some guys drill holes thru the Hysol to be able to rib lace. I left the gap there and braced the tank against the #3 rib web with some small wood blocks. I believe John McBean suggested this.

Jim

[Dave Holl]

I did the same as Dave S did. Pollytac the ribs pre coat of polybrush
to the top of the tank and rib stitched all the ribs except no1 rib. The frabric was most certainly stuck to the top surface of the tank after that process!
I think the reason why polytac is not used on the top surface of the tank is one the area to polytac is large and as you low it dries very quickly two you need to heat shrink the fabric and three the pre coat of polybrush heat shrink and then good topcoat of polybrush does a good job!
Anyway it worked for me!

[MotReklaw]

I drilled through the hysol on my rib 3. Used a spacing of 1.75" and sewed the fabric down. I used that close spacing because it was within the prop zone plus one bay rule that Stewart recommended. It was interesting lacing on the left wing. Had to use left hand knots and a real skinny wire to pull the thread through those small holes. I've thought about riveting rib one. May still do it before I paint, rib 10 also.