is this normal 7 Horizontal stab front spar

[PaulvS]

Mine is an older kit and I did not have that issue because all cuts, bends and holes need to be done by the builder from raw stock. It's more work, but there is wiggle room to get the parts to fit.

You should be able to tweak the bends without work hardening if the amount of re-bending is limited, also because the total displacement is only 6 degrees. Just make sure to maintain minimum bend radius 1/8" and no marring of the parts.

What does it look like if you put a couple of small C clamps either side of the bend line? That should help to confirm what adjustments need to be made.

[swift12]

Thanks Paul.

I think its the HS0001 pieces. They definitely have a reflex in the bend area and for the thickness man those bits are strong....I cant pull the gap down with an Irwin grip clamp. its a little bit of this and a little bit of that all contributing and now makes me wonder if I need to tweak those hs0001 pieces.

[RV7A Flyer]

Originally Posted by swift12

Hi. Building the horizontal stab front spar.

small gaps either side of the bends between the 714/710 and 702. will these pull up when riveted?...it seems that the hs0001 parts both have small bends each side of the factory bends across the length of the part which doesnt help the problem. maybe its because the 710/714 parts are thicker so even though i was very careful to get the bends in the right place i think their radius is more gentle than the 702 and hs0001 parts. the 702 bend sits hard on the 710/714 bends with the small gap either side. all parts are 6 degrees. anyone else looked this closely or seen this?
all ok? I cant see how i could rectify it without mucking around with the 710/714 bends and possibly making a mess.

build on and trust the rivets will pull them together? the pic shows a small gap on the left side of the bend...hard to photo...all four joints look the same...cheers.

I can't tell you how to fix it, but I would say that relying on the rivets to "pull it together" is not a sound construction method. Parts need to fit properly *before* being riveted. Redo the bends, remake the part, whatever, but this is the empennage, and a failure here could end in a very bad day. There will be lots and lots of little issues like this on the rest of the build, so you might as well get used to sorting them out properly now.

Not being critical, just advising on "build mentality". And if you're concerned about it now, are you going to be less concerned barreling along at 170 knots later?

I'd start by carefully measuring all the parts and comparing to the plans to see where things went wrong. A call to Van's (and better pictures) might also help. Also, check for absolute flatness of parts...a lot of them come from the stamping process with a slight curve that needs to be removed (forcefully for thicker parts).

[swift12]

Originally Posted by RV7A Flyer

I can't tell you how to fix it, but I would say that relying on the rivets to "pull it together" is not a sound construction method. Parts need to fit properly *before* being riveted. Redo the bends, remake the part, whatever, but this is the empennage, and a failure here could end in a very bad day. There will be lots and lots of little issues like this on the rest of the build, so you might as well get used to sorting them out properly now.

Not being critical, just advising on "build mentality". And if you're concerned about it now, are you going to be less concerned barreling along at 170 knots later?

I'd start by carefully measuring all the parts and comparing to the plans to see where things went wrong. A call to Van's (and better pictures) might also help. Also, check for absolute flatness of parts...a lot of them come from the stamping process with a slight curve that needs to be removed (forcefully for thicker parts).

Agreed. Vans says looks fine but I’m going to rework it. If it’s not easy I’ll buy new parts. Hs0001 does have stamp curves and for a thin bit of metal it’s **** tough and springy. It’s just the worst of the curve is concave immediately behind the bend. I have to flatten each side without creasing anything. One thing I’d have to say is that I bet mine is not the only one and there will be many like this just not either seen checked or worried about. As above possibly one of the reasons cracks have happened in hs702? There is no way everyone out there has got these bends all perfect I’d imagine. So I’ll fiddle with it and post results. Cheers.

[swift12]

So I got it a lot better. I think the bend radius of the hs710/714 pieces was one of the issues. Also I might have bent slightly outside of the bend. I made a solid ali former with a 3mm radius. Ran it up to the bend line and there was a small gap close to the bend. I used a hardwood block and gave each one a blow which helped. It appears the bend radius are tighter on 702 and hs0001. Also hs0001 we’re both at 6.8 degrees from the factory so I eased those back to 6 degrees. No matter how hard I try they don’t nest perfectly all the way to the bend but do appear to pull in very close which I believe riveting will fix. I resisted unbending and rebending….just tweaking here and there.

[Taltruda]

Looks better! Try pulling them in with those wing nut clecoes if you have some while you rivet.. that may help keep everything tight!

[Pip]

Looks great (nice catch). I am ready to bend these now, can you post a pic of the form you made?

Thanks,
Pip

[swift12]

Originally Posted by Pip

Looks great (nice catch). I am ready to bend these now, can you post a pic of the form you made?




Thanks,
Pip

I only made the former (straight ali piece with a 1/8" radius on the end and held in vice) to try and take some curve out of the 710 and 714.

what id suggest is this if i were doing it again.

Make a 6 degree ali template with a 1/8" radius or put the 6 degree lines on your bench. bolt a block to the bench on one line...clamp another block to it...sit the L shape of the 710/714 on the bench...bend it to the 6 degree line...(have to go just a little past for spring back)
definitely dont use anything other than hardwood or aluminium to clamp the parts while bending and the main thing is get the bend in the right place...so the middle of the radius need to be in the middle of the bend.

The check those striffener parts as mine were over 6 degrees from the factory.

when you fabricate the 702 parts and you flatten the flange out it leaves those bits not perfectly flat....so work on that area....i found they will hold up the stiffeners slightly....I filed a few small areas flat but not near the rivet hole.

good luck i have spent far too much time on this part because my bends were not perfect at the start and i think needed to be very slightly further inboard. i bent in the right place but the wood i used was pine and i think crushed slightly leaving more of a curve than a nice 1/8" radius.

If it were not all match drilled id be replacing the parts and trying again. I figure I have not work hardened the 710/714 parts as i have not bent and re bent them...just a little tweaking....and a lot of HS's out there wont even have the stiffeners so i imagine strong enough.

[Pip]

I got it now! Thanks for the detailed reply.

Pip

[swift12]

Originally Posted by Pip

I got it now! Thanks for the detailed reply.

Pip

Good luck. If you are anal like me it’s a hard job. Guess I need to ease off