Tonight I was reading ahead on page 06-07 where the fin structure is installed into the main fin skin. I noted the note about not forcing the ribs and deforming the skin. I'm waiting for a nutplate from Vans that I decided to replace after I had to remove a rivet I was not happy with so I thought that I would do some trial fitting of the various components into the skin. First i fit the front spar and lower rib VS-1202 and VS-1208 which I had completed connecting except for one of the nutplates. It fit Ok except at the nose of the VS-1202 front spar at the front bend area of the skin. The last two holes in the rib would not line up because the piece would not push into the bend area sufficiently. It appeared the front end was too tall on the rib. I had done the radius work per the dwg but that did not appear to be the issue. I looked at the interference area and ended up filing some of the front end at the upper and lower corners away. Putting it back in and out twice I got it to Cleco up without adding a signiciant amount of force. It still appeared to me to be very tight. I put rib VS-1207 in place and it fit fine. Next I decided to try the upper rib VS-1205. I could not get it into place front to back. It is nearly a quarter of an inch to far back per the hole locations on the skin. The front end will not push any further forward. I did some work on the front end of the rib to the point that I am not happy with what I have done and the rib still is not close to fitting. I installed the rear spar in postion just to make sure the geometry was OK and it was. I took a measurement at the location of the two front most holes in the skin where the front rib holes should align and got a gap between the upper and lower holes of between 0.95 and 0.99 depending on how much the skin is deflected from its natural bend. I measured the front end of VS-1205 at the hold location and the rib is 1.19 high at that point. That tells me that I would have to grind off and taper the front end of the rib back past the last ears where the last mounting hole is. I'm sure that is not right so I'm wondering if it is possible that my fin skin has the wrong radius bend at the front. Is that possible? Thought I would ask for advice here before I call the Van's help line. I keep thinking I'm doing something wrong but if I am I'm not sure what. Did anyone else have fit issues like this? Already learnin a lot as a first time builder.
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Fit of Ribs in vertical fin skin
- Thread starter hjd3021
- Start date
XOverZero
Well Known Member
Just finished the VS a few days ago. Obviously, I can't say whether your VS skin leading edge radius is off, but it seems very unlikely. If it is, then the VS-1204 forward skin certainly won't fit, because the LE radiuses of the two skins fit together very closely.
I did have to manipulate the forward spar and the upper rib to get the forward-most rivet holes to line up. I rounded off the forward tabs and filed their front edges a bit thinner as recommended, but then I also had to change their shape a small amount. Those flange tabs as received are essentially flat. They need to conform more to the skin contour. Adding a little more curve to them was pretty easy, I just had to take care not to overdo it.
When cleco-ing it up, start with the second rivet hole back from the LE. Then you should be able to align the first hole in the skin with its mate in the rib and/or the front spar. Use a tapered pin punch to GENTLY coax the holes into position, then drop in the cleco. A helper wouldn't be a bad idea here, but it is doable solo. Get clecos into the first two positions on both sides of the stab, then proceed with cleco-ing up the remainder of one entire side, and then flip it and do the other.
It takes a bit of patience and finesse, but once you get all the clecos plugged in and ready to start riveting, you'll be impressed with how exceptionally well it all fits together - very tight and solid. There is not the least bit of slop anywhere in the structure.
One final tip: I found that back-riveting the front nut plates produces a nice, clean result - no stretching or distortion of the skin.
Best to you.
I did have to manipulate the forward spar and the upper rib to get the forward-most rivet holes to line up. I rounded off the forward tabs and filed their front edges a bit thinner as recommended, but then I also had to change their shape a small amount. Those flange tabs as received are essentially flat. They need to conform more to the skin contour. Adding a little more curve to them was pretty easy, I just had to take care not to overdo it.
When cleco-ing it up, start with the second rivet hole back from the LE. Then you should be able to align the first hole in the skin with its mate in the rib and/or the front spar. Use a tapered pin punch to GENTLY coax the holes into position, then drop in the cleco. A helper wouldn't be a bad idea here, but it is doable solo. Get clecos into the first two positions on both sides of the stab, then proceed with cleco-ing up the remainder of one entire side, and then flip it and do the other.
It takes a bit of patience and finesse, but once you get all the clecos plugged in and ready to start riveting, you'll be impressed with how exceptionally well it all fits together - very tight and solid. There is not the least bit of slop anywhere in the structure.
One final tip: I found that back-riveting the front nut plates produces a nice, clean result - no stretching or distortion of the skin.
Best to you.
John,
Thanks for the information. I will take a look at the issue with the tabs to see if that appears to be the issue. I took some pictures late last night that I will get posted to my kitlog link tonight. It just appears to me that I can't get the rib far enough forward to line up the flange holes as the rib appears to be much higher than the space it needs to fit. Your idea of checking the forward skin is something I did not try - I will do this as well to see how it fits. I still have one hole in the forward spar rib also that is not in proper position to cleco - the hole closest to the front of the rib. Again it appears that the rib is to high at that point to be pushed far enough forward ( to the side) in this case. I'll spend more time looking all of this over later this week - work is going to keep me from it until later in the week! Sometimes stepping back and then reanalizing the situation helps.
Thanks for the information. I will take a look at the issue with the tabs to see if that appears to be the issue. I took some pictures late last night that I will get posted to my kitlog link tonight. It just appears to me that I can't get the rib far enough forward to line up the flange holes as the rib appears to be much higher than the space it needs to fit. Your idea of checking the forward skin is something I did not try - I will do this as well to see how it fits. I still have one hole in the forward spar rib also that is not in proper position to cleco - the hole closest to the front of the rib. Again it appears that the rib is to high at that point to be pushed far enough forward ( to the side) in this case. I'll spend more time looking all of this over later this week - work is going to keep me from it until later in the week! Sometimes stepping back and then reanalizing the situation helps.
XOverZero
Well Known Member
Glad to, Mate...
The solid rivets in the nutplates in the VS main skin are usually set with a squeezer. In that particular application it was pretty awkward (to me) to do it that way. I practiced first and learned that, due to the mass of the tool and the thinness of the material, it was difficult to hold everything steady enough to prevent the operation from stretching and distorting the edge of the skin. The end result would be a somewhat wavy joint line.
In back riveting, the rivet is formed with a gun, rivet set, and a flat steel plate serving as the bucking bar. However, their positions are reversed from normal. The manufactured head of the rivet rests against the plate and the gun/set is applied to the tail of the rivet. The flush rivets are held in place in their dimpled holes with tape, the assembly is placed on the plate face down, and the nutplates located on the rivets. A special back rivet set is used to drive directly on the rivet shank to form the shop head. I found it to be the best method for holding everything dead steady, and creating a very clean, crisp installation.
Check with the tool vendors who advertise on this site. They sell the back rivet sets, plates, and tape, all of which are pretty cheap. I got all my riveting stuff from Cleaveland Aircraft Tools.
Hope this helps.
The solid rivets in the nutplates in the VS main skin are usually set with a squeezer. In that particular application it was pretty awkward (to me) to do it that way. I practiced first and learned that, due to the mass of the tool and the thinness of the material, it was difficult to hold everything steady enough to prevent the operation from stretching and distorting the edge of the skin. The end result would be a somewhat wavy joint line.
In back riveting, the rivet is formed with a gun, rivet set, and a flat steel plate serving as the bucking bar. However, their positions are reversed from normal. The manufactured head of the rivet rests against the plate and the gun/set is applied to the tail of the rivet. The flush rivets are held in place in their dimpled holes with tape, the assembly is placed on the plate face down, and the nutplates located on the rivets. A special back rivet set is used to drive directly on the rivet shank to form the shop head. I found it to be the best method for holding everything dead steady, and creating a very clean, crisp installation.
Check with the tool vendors who advertise on this site. They sell the back rivet sets, plates, and tape, all of which are pretty cheap. I got all my riveting stuff from Cleaveland Aircraft Tools.
Hope this helps.
If one does not already know how to use a rivet gun, I would not think that this is the place to start!!! I think almost all RV12s are built without the single use of a rivet gun, I know mine was! Getting the first tail kit is a big deal to us first time builders - I remember worrying about almost everything. Don't let reading this forum distract you into some method that might (or might NOT) be "slightly" more optimum! Follow the plans, squeeze the rivets, and keep going. You will learn a lot from completing the tail and there isn't much you can mess up on! You will then have more discernment in evaluating alternative methods!
XOverZero
Well Known Member
Hi John & Bill, thanks for that discussion. I have previously done a very minimal amount of rivet setting with a gun, but for the RV12 I do not have a gun, bucking bar, or most times an assistant: I will stick to squeezing the solid rivets carefully. Thanks again for your help, Dino...
I am probably where you are at. I bought those rv-12 homebuilder help videos and reviewing those it is suggested that you open the skin and cleco from the front. I noticed in the video and while deburring the holes, that gently opening the skin helps with the clearance issues. Cleco one side from the front back and then work on the other side....then rivet from the front back. Vans' airfoils are pretty dang fat so they are a tight fit into these skins.
I have finished my skeleton and I test fit each of the radiused ribs and front spar for fit after I deburred them and radiused them on the grinder and fluted them as appropriate.
So far so good.
I do recommend those videos btw, reading the plans, then watching the videos and then re-reading and checking each step off as you go helped. Bringing your laptop into the shop so you can review them as you go helps as well.
BTW - on nutplates - I had my oldest son helping me dimple the no 8 nutplates last night and showed him one or two and then let him do the rest only to notice when he said done that he used the K1000-3's for his lot! Arghhh! My fault for not showing him which ones to use. Now to order some 18 of those this morning.
I have finished my skeleton and I test fit each of the radiused ribs and front spar for fit after I deburred them and radiused them on the grinder and fluted them as appropriate.
So far so good.
I do recommend those videos btw, reading the plans, then watching the videos and then re-reading and checking each step off as you go helped. Bringing your laptop into the shop so you can review them as you go helps as well.
BTW - on nutplates - I had my oldest son helping me dimple the no 8 nutplates last night and showed him one or two and then let him do the rest only to notice when he said done that he used the K1000-3's for his lot! Arghhh! My fault for not showing him which ones to use. Now to order some 18 of those this morning.
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That's a good idea, although I might be worried about the integrity of the metal around the rivet holes. I found them for 50 cents each on aircraft spruce and I needed some other stuff anyway.
