B

BryanArd

Active Member
Sponsor
Hi guys, I just closed my -4's right wing. Everything looks great, except for the top, outboard skin. At the flap/aileron junction, on the trailing edge, there is a wave. It looks as if the metal stretched while riveting, so it does not lay down flat. I think the skin needs to be shrunk to make it fit nicely (it is the part that overhangs the rear spar).

1) Does anyone have any experience with a stretcher/shrinker?

2) What will the skin look like after shrinking?

3) Will small amounts of bondo and primer make the finish look OK, or is that just wishful thinking?

I don't mind minor imperfections, but this sticks out like a sore thumb!

Thanks
 
If you're talking about the standard stretcher/shrinker with jaws and hand actuated leaver, it will look horrible, and will do way more damage than good. I tried it on a scrap of aluminum once. The jaws will leave deep marks, and the aluminum doesn't hold up well to being mechanically pushed around like that. That isn't what you're looking for.
 
I used a shrinker pretty aggressively to get the front of my tip up to match with the boot cowl. It does leave v shaped grooves that have to be filled and sanded but there is a lot of canopy stuff that needs to be filled and sanded. I'm glad I did it rather than try to build a new canopy. No one has ever noticed; well at least until now.

I was dealing with a curved surface. With a flat surface a little would go a long long way.

Edit: Upon further reflection I guess I agree with Scott. I think with a flat surface, if you used a shrinker on the edge you would have massive problems with ripples and such since you couldn't shrink the whole surface proportionately.
 
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Shrinker/Stretcher

The canopy side skins on the RV4 come from the factory with some shrinking and stretching already done to it. The forward upper corner has been stretched and the lower middle aft has been shrunk. I happen to have a photo that shows what it looks like (see below). I think shrinking is a reasonable alternative. The tool is not that expensive but I have never used one.

Sincerely,
Brian Vickers, RV4 finishing

my.php
 
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Shrinker

I'm not sure about shrinking a flat skin, but they can do wonders on curved skins.
I was fitting the fwd baggage door on the twin 8's and even with the new prepunched kits I wasn't satisfied. The friend that was observing/helping said " I wonder if a shrinker would help", and I remembered I have one.
If you're having trouble with your fwd. baggage door fit, beg, borrow, or steal a shrinker, it works wonders!
 
Old kits...

Bryan,

On my -6A wing, I had some errors in the same location dues to the rear spar top flange not being straight. I had to put in some shims to level things out between the spar flange and the skin.

First, lay a metal yard stick over your rear spar and see if straight.. since the flange faces aft here, it is easy to remove rivets and add a shim.

If your aileron fairing piece is not yet attached or it's holes drilled, I would recommend updating to the later RV-7 part. It is a quite different design, and with it's 45 degree bent flange, it would tend to straighten out any "ripples" in the top ski overhang. If you have already drilled for the original curved 0.016 aileron fairing, it's too later to consider this upgrade....:(

Try the straight edge over the rear spar and let us know...

gil A
 
az_gila said:
Bryan,

On my -6A wing, I had some errors in the same location dues to the rear spar top flange not being straight. I had to put in some shims to level things out between the spar flange and the skin.

First, lay a metal yard stick over your rear spar and see if straight.. since the flange faces aft here, it is easy to remove rivets and add a shim.

If your aileron fairing piece is not yet attached or it's holes drilled, I would recommend updating to the later RV-7 part. It is a quite different design, and with it's 45 degree bent flange, it would tend to straighten out any "ripples" in the top ski overhang. If you have already drilled for the original curved 0.016 aileron fairing, it's too later to consider this upgrade....:(

Try the straight edge over the rear spar and let us know...

gil A
Click to expand...

Hi Gil. My aileron fairing is already riveted. The wave is on the outboard end of the flap, just to the right of the skin splice.

I will drill out some rivets on the rear spar and maybe some on the splice and see if the skin is under some kind of stress. Hopefully that works. If it does, the holes will have to be drilled out and "oops" rivets used.

Thanks for the response guys!
 
Flat?

BryanArd said:
Hi Gil. My aileron fairing is already riveted. The wave is on the outboard end of the flap, just to the right of the skin splice.

I will drill out some rivets on the rear spar and maybe some on the splice and see if the skin is under some kind of stress. Hopefully that works. If it does, the holes will have to be drilled out and "oops" rivets used.

Thanks for the response guys!
Click to expand...

Bryan... the flatness check is probably still worth doing....

Could you have affected the rear spar flange angle when the aileron bracket reinforcing piece was riveted on?

gil A
 
Bryan

this is my first post @Vansairforce and if I can give you some friendly advice it's a great pleasure for me.

I am frequently using the Lancaster shrinker with modified jaws from TM-Technologies in my workshop (car & motorcycle restoration). It only leaves sandpaper marks on the sheet. Kent of TM-Tech manufactures the jaws himself (I actually did observe him doing it) and I can say from experience that they work wonders. Obviously the shrinking factor cannot be as aggressive as with the normal jaws but I think your problem will be solved.

If you want to have a look www.tinmantech.com
http://tinmantech.chainreactionweb....prod242&cart=837b4162e995a4b36ef86030ab189f1a

Axel
Rueti, Switzerland, still dreaming of building an 8
 
Gil, I will do just that. Thanks for the help!

Axel, I think that if what Gil said doesn't work, then those new shrinker jaws just might fix my problem. Thank you very much!
 
Timely Advice

az_gila said:
Bryan,



If your aileron fairing piece is not yet attached or it's holes drilled, I would recommend updating to the later RV-7 part. It is a quite different design, and with it's 45 degree bent flange, it would tend to straighten out any "ripples" in the top ski overhang.

gil A
Click to expand...

Gil,
I'm about at the same stage on my -4, trying to set the aileron position but not quite to the seal. Do you have pix of the -7 part? I might consider switching to that, instead.
 
Picture to come...

WSBuilder said:
Gil,
I'm about at the same stage on my -4, trying to set the aileron position but not quite to the seal. Do you have pix of the -7 part? I might consider switching to that, instead.
Click to expand...


Updated with picture...

Aileron-seal-update.JPG


The part is W-724-R & L
It is a little longer than the -6 part... the lower picture shows my rough cut of how much needed removing.
Some clearance holes need to be added for the round head rivets holding the ribs on... the flush head ones per the old plans are now in the wrong spot.
The aft edge can be dimpled and 3/32 flush riveted, and I will secure the spar side with LP4-3 rivets per the original fairing...

This new part is easier to install, and may slightly adjust the curve of the overhang if needed....

If you are building a -4 or -6 and have not come to this part, I would recommend the change as an upgrade...


gil A
 
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Hi Gil, I would like to let you know that I drilled out about 12 rivets on the rear spar. I then put a shim under the outboard skin, and that eliminated about 98% of the wave in the skin. I can probably put a small amount of pre-load on the skin and make it lay flat on the flap!

BTW, I did re-rivet the ones I drilled out!!!
 
Glad it worked....

BryanArd said:
Hi Gil, I would like to let you know that I drilled out about 12 rivets on the rear spar. I then put a shim under the outboard skin, and that eliminated about 98% of the wave in the skin. I can probably put a small amount of pre-load on the skin and make it lay flat on the flap!

BTW, I did re-rivet the ones I drilled out!!!
Click to expand...

Great... my wing rear spar had a "hollow" in this area, and needed a long shim across the top...

Sounds like yours was simliar....:)

...ahh... the pleasures of the old kits before Van got his NC equipment...:D

Also, a much better solution than shrinking....

gil A
 
Airflow?

Gil,
Great pictures. Thanks! I have to wonder about the geometric differences between the two seals. The original looks like it makes for a smaller gap and therefore reduced drag at cruise. The newer faceted design might give better roll authority at low speed, though. Definitely easier to install, but not a big factor. Would any of the aero guys be able to comment?
 
RV-7 aileron fairings

Has anyone used the RV7 aileron fairings on an RV6 as Gil suggested? I am now trying to hang my ailerons and flaps and just read Gil's suggestion of using the update on a 6 and was wondering what if and the effects and consequences of doing so. Any thoughts?
 
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