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RandyL
10-11-2008, 10:45 AM
My SS kit had the initial fabric installed on the HS and elevator. I see two things that concern me and I need some advice on.

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The first pic is a frame bump on the HS leading edge that protrudes, and the next two pics are of a slitting technique used on the corners of the elevator and HS. Do these issues need correcting? I have no problem removing the fabric and starting over if they're not up to standard.

Mark
10-11-2008, 11:43 AM
Randy,

The first photo is a weld between the tube and cross member. The best way around this is to body work it before covering. (It would take away too much material to grind the weld down.) As long as it's not sharp, it's ok, other than aesthetics.

The other photos demonstrate what the Kitfox cover manual shows for a technique of slitting around rounded edges. Although the radius here is large enough to heat work the curve without slitting. The slits will show under the finish tape.

Before ripping off all your cover, you might try Superfil and body work these areas smooth. Then apply you finish tapes.

Dave S
10-20-2008, 06:33 PM
Randy,

Here is my take on what you are looking at with the horizontal stabilizer questions & Fabric.

1) The bumps you see through the fabric just behind the leading edge of the horizontal stabilizer is probably the weld bead for one of the steel ribs which make up the structure of the horizontal stabilizer. If the fabric is stretched tight over the weld bead and there are no sharp protrusions from the bead, it is probably not going to be a structure issue with the fabric covering - also this portion will get a layer of tape over the leading edge which will provide additional strength. This is more a matter of aesthetics than anything else; and, aesthetics is a matter of each person's views of such things in light of how much additional work one wants to get involved with. If you eyeball a utility fabric covering job on an old Cub, Tripacer or Taylorcraft, there are all kinds of little bumps under the fabric. The weld beads stuck up a bit on my horizontal stabilizer also; and, I added a bit of epoxy filler to smooth out the bumps - more to make it look smoother through the fabric than any other reason. The critical thing with the fabric is that a person does not ever want a sharp edge or point poking up from the inside - while the fabric is extremely strong, it cuts pretty easy.

2) For the curved parts of the horizontal stabilizer where the slitting technique was used to get around the corner; again, this is a method that people do use. Otherwise, a lot of people will work the fabric around the curved leading edge with a shrinking iron in place of doing the slits - which results in a very smooth appearance. One thing I can tell you is that any slit edges, such as the strips in the photos, will show through the remainder of the layers - it won't become less apparent, it will become more apparent as the final paint goes on. I think this is less a matter of strength and more a matter of aesthetics - just depends on what a person wants.

On my elevator, I had an awful time getting the fabric to shrink down around the trailing edge where it met the much bigger elevator front spar at the root - I ended up removing the fabric and fabricating foam blocks to make a smooth transition (sort of like on the ends of the horizontal stabilizer) - then I was happy with it.

What fabric covering system are you using on the airplane?

Sincerely,

Dave S
St Paul, MN

RandyL
10-20-2008, 07:08 PM
Thanks Dave. I'm using the standard Poly Fiber system. This is tough because being new to fabric I don't yet know if I can improve on what's already there. Being the quasi-perfectionist I am I'm inclined to remove all the covering and...

1) grind down the weld so it won't protrude

2) attempt to use the iron method rather than the slits to get the fabric to wrap around the corners. We learned this in the SportAir class I took. I'm just naive enough at this point to think I can do it. Gotta try at least. :o

I know this would eat at me if later if I didn't at least attempt to improve it. That's the great thing about fabric, it's relatively cheap and easy to start over.

wadeg
10-21-2008, 01:01 AM
Randy,
It's easier than you think. Just give it plenty of tension and let the iron do the work. After you've made it around the bends (in tube), the fabric will essentially be 'holding' around the tube and keeping form. Just make sure you put a line of polytack along where you will then cut it with your fiskars to avoid fraying. Let me know if you want help. It's a lot of fun working with the fabric and learning its 'personality' and I now don't regret all those years/money growing up ironing monokote down to model airplanes!
Wade

Dave S
10-21-2008, 05:36 PM
Randy,

You won't go wrong with polyfiber - there are other systems, and polyfiber is one of a number of systems that work well and will last a couple decades.

I think you pretty much answered your question when you mentioned that you are a quasi-perfectionist. The part you are considering recovering is not too big of a deal if you do re-do it to your standards you will be happier with the end result. There is more than once I re-did something until I was happy with it. The reason we build airplanes is so can have what we want rather than putting up with "just ok"

If you haven't worked on fabric before, I don't think that should be a concern. In my case, I had an opportunity to do a few control surfaces on a friend's piper - a little practice like that helped a lot - but I didn't have any other prior experience. One of the things I found most useful was to buy the Poly Fiber manual - if a person reads, studies and takes their time - you will be surprised how quickly a person can pick it up. The manual covers everything; and, since I did it - it is obviously Norwegian proof. The rib lacing & knots on the wings seems a bit confusing at first. The trick to that is to take the book, the needle, some thread and a practice piece - lock your self up in solitary in the hangar and you will emerge 3-4 hours later with the skill mastered.

Your experience in the SportAir class will serve you well - you will find that the iron is the master tool for covering.

I thought about grinding welds too; however, the thought evaporated real, real fast because I didn't want to take any chances of unknowingly weakening anything - That is why I went to the epoxy filler to smoothen things out a bit - not saying I know much about grinding welds and strength of the weld - just decided to avoid it because I wasn't sure.

Sincerely,

Dave S
St Paul, MN

Bryan
10-21-2008, 07:39 PM
If the bump is really bothering you here is how I would go about taking care of it. I would use a dremel tool with the fiberglass cutting wheel, and I would grind the bump off. Do this in a way as to keep metal pieces and the sparks going away from the rest of the part. The dremel when used slow works well for this. You really just need to go slow and be careful. Then I would patch this area and then the finish tape should cover most of the patch. So it really boils down to seeing a patch or the bump.
As far as the fabric around the corners I would try to use the iron and get the edges of the slit pieces to lay as flat as possible and with a little work these can really lay flat and then the finish tape will cover these very well. Don't forget about trying bias finish tape. It really forms around corners well. If you try this and it just does not look as good as you want then cut it off and go again. I wish you were closer as I would be willing to help you out on the cover as I really enjoy this part of a build.


Good Luck
Bryan