Thorp Air Command - T18.net

I'm am rebuilding damages S wings.

Both outer panels will need to be reskinned along with some rib replacement and right rear spar replacement.

Anyhow. I am concerned about a couple of things.

One is errors in not drilling out every rivet correctly. Resulting in an Elongated hole in the rib. There are solo many rivers it is bound to happen I would guess despite my best efforts a number of times. What do I do in those cases?

Secondly, even of I properly remove the rivet, does the riveting process expand the #30 hole? In other words does the expansion of the rivet shaft stretch the original dimpled hole?

Should I re-dimple the remaining rib? Will this help shrink the hole back closer to the original #30 hole?

Finally I'm looking for ideas as to how to locate ALL the holes into the new skin. These have ta be exact I would imagine and every dimple will have to fall into place. It would seem nearly impossible for soooo many rivet dimples to ALL line up exactly. The rivet hole duplicators I have seen are limited in length to maybe 18 inches or so. I will need to duplicate well into th skin sheet which I would think exceeds the length of the duplicators. Does someone have say a broken band from a band saw that I could make as set of "extended" duplicators? Are these duplicators even that accurate?

Am I making a bigger deal out of this than it is? Or should I just pony up the cash to buy all new ribs and be done with it?

I have a damaged vertical fin to drill out rivets for practice, along with the known ribs to be replaced for additional practice to help perfect my rivet removal techniques. So hopefully that will help minimize the number of "oops" I make by not perfectly drilling out rivets.

Thiughts?

Hi Tom;

1. never drill through. just go deep enough so you can break the heads off with a pin punch. If you drill in the center of the rivet, and if you don't go too deep, you can't elongate the hole in the rib.

You just have to make a concious decision that you are ALWAYS going to do it right.

2. The riveting process does not change the diameter of the hole. However, the dimpling process does. Normally dimpled holes are drilled to fractional size and they open up a little after dimpling.

3. Don't redimple holes! Aluminum hates to be bent forth and back. It's a recipe for cracking.

Looking forward to tips from the more experienced folks on how to drill the new skins to match. YES, the locations have to be exact. Each and every one. I once saw a crew of Boeing metal guys re-skin the belly of a 737. They flattened the old skins and used them as patterns for the new skins. However, in your case the bent leading edge complicates the process. You can make your own strap duplicators, but I don't think that method will work here...... you want the new skins to be tight on the ribs when you drill.

Good luck!

D

If you prefer to match the old holes use the old skin and make a transfer strip.

When reskinnig its best to change the rivet pattern and place a new hole spaced between the old ones and skip the existing holes.

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD

Happy Easter!


The problem with putting new rivets between the existing rivets, is that in many cases that is where a flute is on the rib flange.

I assume if it is NOT a good idea to re-dimple the rib flanges due to cracking potential. I would think it not a wise idea to flatten the flute and then flute it in another location. But this would be nice so that a simple pattern strap can be used and result in nice rivet lines.

I think that I will either make from scratch but probably just buy from Cubes all new leading edge ribs.m as it is already a wet wing and they may be destroyed or will at least I will have new leading edge ribs to construct the new wet wings.

Back to drilling out say #30 rivet, should I drill the center with a 3/32" bit. Then follow up with 1/8" and only use a #30 for a small amount and then use a awl or small punch to try to pop the remaining flush head off?

I have found it difficult to get exactly in the center of the rivet. Even if the manufactured dimple is there. Also I have even tried to enlarge the simple with a punch. But still the bit sometimes wants to "walk".

I think some of the rivet heads may have been left a touch high. Then sanding and paint made the dimple all but invisible of not completely invisible. I have removed the paint and that sometimes reveals the dimple, sometimes not.

There is no issue with going in between the existing rivets. When able this is the recommended practice. I'm not sure what you mean by the existing dimple but there is plenty of room to split the middle and create a new hole and dimple.

_________________
Lee Walton
Houston, TX
N51863,N118LW
KEFD

I agree with Lee. Of course the easiest way is to start over with new ribs. The old skin can be used as a pattern. Just fold the new skin inside the old. Or you can cut the old into locator strips. Tons of ways to skin this cat/rabbit.
Cubes

The dimple for drilling out, o was trying to describe is the manufactured marked center of the rivet head.

The spacing for the rivets is not the problem. The existing ribs I have are fluted on the flange. The flutes were located between the rivet locations. So that now if I place the new rivets in between many of the new river locations will occur in the same place as a flute in the rib flange. So I would have to flatten the existing flute out and then add new flutes into the rib to maintain there is no rib warp.

I would assume I would need to also keep the first and last existing rivet at the spars or ends of the skin. Plus the new offset rivets to be centered between the old rivet holes.

sounds like it may be easier to just make a new rib?

I have started drilling out the skin rivets.

One question I had is that some of the rivets (mostly in the damaged area) are lose and start to spin when I only get a short way in after starting to drill it out.

How can you stop a rivet from spinning so that it can actually be drilled out?

I tried holding a punch on the rivet etc and everything I have tried has not worked. Does anyone have a trick to this?

Super glue......or re- rivet

Do you have access to the shop head of the rivet ? If so can you put a pair of Vampliers on it to keep it from spinning ? Or maybe a small pair of mini vice grips ? Yes Virgina there are pliers called Vampliers ! I have a pair of the large and mini ones . Paid for themselves the first time I used them . Not for rivets , but for removing broken off screw heads . Most aviation tool houses have them or just google them there pliers .

If I were to tackle this project the first thing I would do is order a set of new ribs from Cubes . I think you will find yourself spending way more time trying to salvage this repair than if you get U sum new ribs !

RB
NX115RX

I am planning to buy all new nose ribs. As the wing is a wet wing and I want to re-do the wet wing. However I have doubts as to with the fuel seal on the ribs, I doubt I will get them out without damage.

Since I also will be needing at least 2 or 3 new ribs for the outer panels. I am heavily leaning towards buying all new main ribs as well and just start fresh. That way I ONLY will have to match the existing holes and dimples for the top and bottom of both main and rear spars.

I will still try to "save" the ribs that I can. Maybe someone else will be able to put them to good use. Besides, all the practice of drilling out the ribs will hopefully allow me to "perfect" my skill before I take on the rivets in the spars. As I hope to save the spars both front and rear (except the section of rear spar that is damaged and must be replaced).

I did think about superglue. But then I'm not sure I could pop the head off very well after I drill it out.

I think eventually, I have enough rivets removed that I should be able to sneak in under the skin to grab hold of the shop end of the rivet. So grabbing it with a vise grip or something did come to mind.

The one thing I noticed about the nose ribs with the fuel seal. NONE of those rivets would spin!!!

Question.

When reskinning, I will need to transfer the exising holes in the spars to the new skin. My understadning these are all #30 rivets.

I do not have transfer punches. So I am wondering if a #30 transfer punch is needed or whether a 1/8" fractional punch can be used?

If there is a #30 hole in the spar cap. Will a #30 punch fit in or will it be too tight?

I have to assume if a #30 rivet will fit through the hole, so will a #30 transfer punch.

#30 = .128; 1/8" = .125 or use a #30 Whitney punch as a transfer

I'm trying to get my list of tools and things to buy or order at Oshkosh.

Are you saying that either transfer punch 1/8 or #30 can be used?
Maybe a silly question.

When I Google Whitney punch. I only come up with a bench or hand type device to punch holes in metal. I'm not sure how I could use that to transfer through the bottom of the main spar cap to the bottom of the new skin other than at the edges. I guess I could see using the Whitney punch for the rear spar.

Or am I completely missing something????

Is this worth buying? http://www.mscdirect.com/product/detail ... 493&mkwid=[*GCLIP*]&prcid=[*GCLSRC]&mkwid=txg6YEZy

I'm still trying to decide if I ought to invest about $220 into a C-Frame in order to dimple the interior of all the skins.
http://www.cleavelandtool.com/C-Frame-B ... 4frloXx_cs

I cannot seem to find a used C-Frame on e-bay or anywhere. Although I have to give a local guy a call who built a RV-9 a few years ago. He might have one that I can borrow/rent/buy as he currently does not have an airplane project currently.

Is a C-Frame used often enough and versatile enough that it makes sense to purchase one. Or is this just a "nice to have" item that I can really get buy without fairly easily when building a Thorp?