Can My Roll Bar Be Salvaged??

[Noah]

No, I didn't tip over. I bought my RV-7A tip-up from another builder with the airframe substantially built. The Cabin Frame (Roll Bar) appears to have some major structural issues. Is this salvageable? Any ideas how?

Here are my concerns:
1. The roll bar is 5/16 higher than the plans call for.
2. The edge distance on the brackets is very small.
3. The edge distance on the roll bar is very small, and breaks through in a couple of places
4. The external bracket has been shaved down to less than half the bracket's original thickness to allow the side skin to sit flush
5. The roll bar is not flat, but rather has an S-bend in it.
6. The gap between the forward and aft halves of the roll bar increases near the ends.
7. The bottom of the roll bar was not notched or relieved to fit over the mounting brackets.

Unfortunately, the baggage canopy/window was already match-drilled to the skin when I bought it, so I can't drop the roll bar without screwing up all these holes. The skin and window are not yet riveted. I need to re-do the canopy anyway because the original was cracked when purchased.

Here are some photos:






[img=http://aycu17.webshots.com/image/33176/2004943369152801736_rs.jpg]





Is this salvageable? Any ideas how?

Thanks,

Noah Forden
RV-7A
Rhode Island

 

[TX7A]

I would.....

make a new one.

I made a new roll bar that had less problems than yours. About 80 bucks and a half day. But, I feel better about it.
However, I have been real picky about some parts....particularly the one's that could play an important part in saving my neck....literally.

Your roll bar may be salvageable but I really couldn't say how. Sorry I couldn't be more help.

 

[craigvince]

Salvage?

Well, here's my 2 cents worth. I had a couple of goofs when I built mine, which wasn't so long ago, so I've dealt with a couple of your issues. Here's my suggestion. Work on the one you have. If you can't salvage it, you're going to build a new one anyway. Don't worry about the scratches. Start with the too-tall issue. Sand/grind down the bottom of the rollbar until it's the right height and fits snugly on the bottom, and is at the right angle. Don't worry about the holes in the rollbar right now. As for the side brackets that were worked down to about half their original thickness, this is common. You have to make them thinner on one side than the other. I think the aft edge was thinner if I remember right.

Once you've got this much to where you like it, and the canopy can fit on properly, then go back to the holes. Take a piece of 1/8" thick aluminum stock and make a thick doubler plate on the inside of your rollbar. Rivet the heck out of it, then re-drill your holes. Remember, if you don't like it, you can build a new one anyway.

Worst case scenario: You're going to royally screw up this first rollbar, and learn all the nuances of fitting it properly. When you make your new one, it'll be a breeze!

Check out my build log for some detailed discussion and pictures.

 

[jsharkey]

Looks fine - Build on!

 

[cytoxin]

trash it

make a new one the edge distance alone makes me cringe.but there is a .040 strap inside. as for the height grinding the bottom means you'll have to make new brackets. i would reccomend making a new one IMHO. oh by the way i did, and my first wasnt near this bad. GOOD LUCK. you dod gring the brakets to match the side skin. and the gap will vary. but typically will be closer on the ends.

 

[Rivethead]

Noah, That's pretty sad stuff there. Your going to have to do something in order to save it. If it hadn't been attached to the brackets already I would say pull it apart and rebuild it correctly using different lacations for the rivets and fill the old ones with body filler, but that thing has been _itched pretty badly so I'd just toss it. They're not hard to do correctly and in the long run, if you were me, you'd be far happier with it. Might I throw some caution your way though. When you rebuild the roll bar (I already know you're going to) ignore the dimension given for it's width on the plans. It was a mistake for Van's to ever have included that dimension in the drawings. That dimension varies from one plane to another. Measure your fuselage and set the dimension to what is in front of you. Don't bother asking how I know.

 

[Captain Avgas]

TOSS IT!!

No, I didn't tip over. I bought my RV-7A tip-up from another builder with the airframe substantially built. The Cabin Frame (Roll Bar) appears to have some major structural issues. Is this salvageable? Any ideas how?

Noah, the workmanship on that roll bar is an absolute disgrace (and that's putting it mildly). Of course it needs to be replaced. No doubt Vans has told you that already.

However based on that one detail my concern would be that the rest of the project might be a closet full of skeletons. I'd get an experienced RV builder or TC to take a REALLY good look at it for you.

 

[Noah]

How about this?

Thanks all for your input and concern on this.

I will agree with all of you, this rollbar attachment IS pretty sad. Before buying the project, I had a tech counselor look at it and, with the exception of the roll bar attachment and the canopy fit, the workmanship is very good (this problem was NOT noted during the tech inspection). I did have to replace a few bad rivets here and there. As I said, the canopy was cracked, so I'm replacing it anyway - I may glue it. Don't worry too much about me, I'm a mechanical engineer and understand structural inegrity and it's importance on a 7A roll bar that I hope to operate off my own grass strip This WILL be done RIGHT, one way or another.

Unfortunately, the issue is bigger than just the rollbar, because the window is clecoed to the rollbar, and that's clecoed to the skin. So changing the rollbar will mean replacing these items too. To refresh your memories the canopy was cracked on the last rivet hole (I think that's why the guy sold it) and I already have a new canopy, which is still new in the box. The back window from the first canopy is OK, clecoed in place.

Here's what I'm thinking (further comments are appreciated):

1. I can't lower the roll bar the 5/16" that's required per the plans without scrapping the currently clecoed tip-up back window over the baggage compartment (or the adjacent skin), and that is not cracked so I'd prefer to keep it. Question is, what ramifications might exist for the fit of the rest of the currently clecoed together canopy frame that I'll be re-building??? If I can't make that work with the additional height, there's no point trying to save the back window and / or interfacing skin.

2. I think I'd like to make new roll-bar attach brackets that are taller than the originals (2.5" vice 2"). The inner attach brackets are OK, it's just the outer ones where edge distance rules-of-thumb are violated. Because the fuselage skin dictates the locations of the forward holes in these outer brackets, and they're drilled already, those holes can not be moved without redoing the rear window or skin. I am thinking of adding a 1/8" doubler 6 or 8 in. long inside the roll bar riveted in 4 or 5 places above the bolts (Thanks Craig). This would help transfer the load from the brackets to the roll bar despite the edge distance problems on the forward bolts. I would also squeeze the rollbar together at the bottom prior to riveting so that the two halves don't spread out at the bottom as they do currently. I would make brand new AFT holes in the outer brackets and put them 1/2" higher (BETWEEN and ABOVE) the original holes so that edge distance rules are adhered to. Hence the need for a 1/2" taller bracket. Finally, the new external brackets would be WIDER than the originals, but ONLY on the VERTICAL flange. The HORIZONTAL flange UNDER the roll barwould remain the same width. This will allow the fore and aft edge distance to increase. The fore-aft edge distances for these countersunk holes on this bracket are too small IMHO, even with the rollbar halves spreading apart near the bottom, which I'm going to eliminate. So I think I'd make the bracket's vertical flange 1/8" wider - any reason not too, weight excepted?

3. I would move the new external brackets inboard, so that the vertical flange doesn't have to be shaved down to wafer-thin thickness for the side-skin to fit nicely. This would require a slight bit of pre-lead on the roll bar, but less than 20 pounds from my estimation pushing on it and seeing how it flexed. Shaving the vertical flange is really questionable to me, maybe it's not supposed to be shaved as much as mine are but if you look at the picture, its SCARY how little material is left. I'd rather move the bracket inboard, keep it full thickness, and shim with custom-made countersunk washers to the skin. This would be a LOT stronger, and not much more trouble. I could find nothing in the plans / manual where it says to shave it anyway - did I miss it?

4. As far as the S-bend in the roll bar, I don't think I could bend this out of it, and if I could, again I'd have to scrap the window as its already drilled but not riveted to the roll bar. Only question is, would the interface and "fit" to the tip-up frame not work or be ridiculously difficult? Since I haven't done one of these, I'm not clear on the flexibility of adjustment there might or might not be - shimming, fit of seals, etc. I'd estimate that the rollbar might have 3/16 or 1/4" of bow to it maybe, tough to say.

If none of this works, I can always buy a new one, and cut a new rear window from the new canopy which is as-yet untouched!

So, what do you guys think of this approach? What haven't I thought of? Thanks again for your thoughtful comments and assistance.

Noah Forden
RV-7A Finishing
Rhode Island

 

[Rivethead]

You've got a new canopy, you might as well use the whole thing. I think in your heart you know you need to replace it all. Once you've brought this plane up to scratch you're not going to want to look at something and know you could've done better.

 

[Mel]

Noah,
Do yourself a favor and do the whole thing over. You will expend much more time and energy trying to salvage something you will never be completely happy with. In the long run you will spend less work to do it right.

 

[LettersFromFlyoverCountry]

I'm concerned about the rollbar, but looking at the workmanship makes me wonder about the rest of the airframe. If this isn't a QB, one would put in well over 1,000 hours of building before getting to this part... and yet, the person totally blew off quality at THIS stage.

It looks like the reason the thing is too high is that he didn't file the base of the rollbar in order to seat it properly around the bottom end brackets. The height difference doesn't bother me THAT much since when you fit the canopy, you trim to get it to drop down to within 1/4-1/2"

But since he's already drilled the rear window, did he drill the canopy itself to the frame? If he did, geez, that locks in a lot of positioning. You can't change the height if the side holes have already been drilled. And if you do, you're gonna have some work to do on the mating of the front and rear.

I don't think it's a lost cause. The edge distance concerns me greatly, though.

But, like I said, you can probably get away with it is as...but if he was this careless 1,000 hours in....well....that doesn't make me real comfortable.

I'd certainly think about a whole new frame, canopy, and rollbar if he's locked in the positioning.

 

[shiney]

replace it and check everything else

I'm working on the roll bar at the moment and whilst care needs to be taken it's not that difficult. Like Bob, after seeing this I would be concerned about the rest of the build quality, this is pretty poor workmanship and the fact that the original builder was happy to have it on his plane bothers me the most.


Shiney

 

[Captain Avgas]

I will agree with all of you, this rollbar attachment IS pretty sad. Before buying the project, I had a tech counselor look at it and, with the exception of the roll bar attachment and the canopy fit, the workmanship is very good (this problem was NOT noted during the tech inspection). .
Noah Forden
RV-7A Finishing
Rhode Island

I'd sack your TC and get another opinion. When I look at the workmanship on that rollbar I see an indication of a builder who has neither the skills, knowledge, patience, or attitude to build a decent plane. Maybe he finally realised that and sold the project. The work on that roll bar is so bad that it is almost certain that a stringent inspection will find other deficiencies in other areas. As Bob Collins pointed out....to see that standard of construction so far down the track must ring alarm bells.

 

[Geico266]

Noah,
Do yourself a favor and do the whole thing over. You will expend much more time and energy trying to salvage something you will never be completely happy with. In the long run you will spend less work to do it right.

I'm with Mel. You won't be happy with the results unless you do it over.

 

[Noah]

Steady-On, Fellas

Easy, fellas... Like I said, I've seen every inch of this airplance and don't have any concerns other than this and a couple of other minor areas I've already corrected. The Tech Counselor for the initial inspection did not see every inch of the airplane. The builder obviously had problems with the roll bar, I have wondered if he was not feeling well the day he did it

Bob Collins says:

since he's already drilled the rear window, did he drill the canopy itself to the frame? If he did, geez, that locks in a lot of positioning. You can't change the height if the side holes have already been drilled. And if you do, you're gonna have some work to do on the mating of the front and rear.

Bob, which holes do you mean by "side holes"? All of the holes in the aft side skin interfaccing with the window have been drilled, that's why I said that I can't change the roll bar height without replacing the rear window and/or skin. The canopy was drilled and clecoed to the canopy frame, but the main canopy is cracked in a few places so its getting replaced. The entire canopy frame assembly was clecoed together (no rivets).

This would beg the next question about whether the tip-up canopy frame should be replaced (not due to workmanship issues, but due to potential alignment issues or due to difficulty match-drilling holes.

Thanks,

Noah
RV-7A Finishing
Rhode Island

 

[Ironflight]

Another Interpretation.....

Several folks have stated essentially that "if the roll bar is that bad, what about the rest of the plane?" A very good question, and one that Noah has answered by stating that he has had the project inspected by several T.C.'s, and that the rest of the quality is fine. SO how can a person's work get worse as the project goes on?

Simple....he loses interest, loses concentration, let's life intrude, makes some mistakes, gets frustrated....and eventually sells the project to someone that can carry it on. Only the later work is flawed, as a reflection of the declining nature of the original builder's interest. I have seen this several times - absolutely gorgeous tail sections that show care and workmanship, followed by declining quality on other components. Put simply....burn out!

I tend to believe Noah when he says the rest of the plane is good, since that has been confirmed by others. I just thought I'd add a possibly different view...

Paul

 

[az_gila]

Easy...

.....
This would beg the next question about whether the tip-up canopy frame should be replaced (not due to workmanship issues, but due to potential alignment issues or due to difficulty match-drilling holes.

Thanks,

Noah
RV-7A Finishing
Rhode Island

Noah.... match drilling a new plexi canopy is easy since you can just look through it....

Since the plexi holes need to be oversize anyway, slight position inaccuracies will not have any effect.

gil A

 

[Norman CYYJ]

Throw out the roll bar and start over. It will be easier and you will have more piece of mind. I f I saw that kind of work on something I would sure think twice about trying to fix it up. In the end you will be happier and a year from now you won't even be thinking about it. If you don't you will be aggravated every time you get into the plane and see it and so will your passengers.

 

[kentb]

Not sure if this will help, but...

If the roll bar ends up being lower then the rear window by a small amount, you can put small washers between the plexi and the roll bar as needed to fill up the gap.

Kent

 

[LettersFromFlyoverCountry]

This would beg the next question about whether the tip-up canopy frame should be replaced (not due to workmanship issues, but due to potential alignment issues or due to difficulty match-drilling holes.

If it opens/closes fine, looks solid... fits OK... I guess I don't see any reason to replace it.

 

[koda2]

Roll bar

Noah,
Let me add my somewhat bitter comments just so you can get one more perspective.
I have already gone thru what you are contemplating, in spades, when I bought a second hand kit (6A). Many of the parts, including the roll bar, were partially completed and some were clecoed on the fuselage. The roll bar had been cut too short and was marginal construction. My attempts to fix it just made things worse.
In addition, I have so far replaced and/or refabricated (in the fuselage), the aft deck, the rear bulkhead, match drilled and replaced both top aft skins, the roll bar, the baggage floor skins, the seat floor skins, and one seat back. Also, the two center seat floor ribs (riddled with holes) were extracted and new ones meticulously fitted, match drilled and replaced. Also, the electric flap support, the forward fuselage skin, the subpanel, and now the canopy frame. The canopy had been trimmed to final size before all these parts were finished and installed, so it may not fit correctly either, I haven't gotten there yet. Furthermore, in disassembly and rebuild, I found some hidden work that was unsat, like countersinking on both sides. There's more gory details, but you get the picture.
I'm no expert 4,000 hr master builder(I make mistakes in building too), but one thing I can tell you for sure; you will spend more time and energy trying to fix something than you will if you just do it over right. You've already got the new canopy, fork out the 100+ bucks, buy the roll bar (and whatever) parts, lay em out on a jig and build em up right. Everything else will fit better. Go over that plane carefully. Don't rely on some third party's offhand assurances, like I did, that its a "great plane." You also won't have any nagging thoughts when you're flying, about those areas you thought were "good enough". BTW, IMO, those roll bar brackets are unsat too. I would remake em.

Dave A.
RV-6AQB

 

[Jamie]

Yep, just build another one.

One hint I would give you when you build the new one -- just drill a couple of holes about mid-way through the arches and cleco the thing down to some flat particle board while you drill the internal strap. It will ensure that the whole thing is completely flat. It also gives you a great reference to ensure that the height it correct. Don't obsess about the height *too* much though -- there is a lot of wiggle room with the canopy fitting.

Here's my rollbar in progress. Notice how I clecoed the thing down using holes drilled midway. All I did was throw some AN426AD3 rivets in those two holes and after paint I really have to look to find the rivets.

 

[mike newall]

Just about the only thing we have goofed on thus far............... fingers crossed.

Build a new one - it will cause problems later with the canopy and then you will be really cross !

 

[N941WR]

You've already got the new canopy, fork out the 100+ bucks, buy the roll bar (and whatever) parts, lay em out on a jig and build em up right. Everything else will fit better.

Dave has some great advice here!

The jig doesn't have to be any thing fancy, just something to hold it in place and keep it "flat" while you drill and cleco.