Author Topic: Mast Repair  (Read 8325 times)

Norfolkfoiler

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Mast Repair
« on: April 02, 2022, 01:52:48 AM »
I read posts on here about repairs eg ponobill

It inspired me to start trying to do stuff.. I seem to have successfully repaired a sabfoil 82 mast that split down the centre near the base plate and lost all stiffness - just laying up 10 layers of new carbon 6 inches up the mast and vacuum bagging. Done 5 sessions on it now.

I want to try to repair another sabfoil 82 mast. The rear bolt snapped (fuselage connection), which then resulted in the front insert getting ripped out. Fortunately did not lose the foil.

Has anyone successfully replaced or reset the barrel nut? My other option is to try to convert this mast to a kraken connector.. I have one of these on order so would try to make a mould based on a new one (not sure how yet).

Any ideas on how best to do this would be amazing…

Wingfoil2001

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Re: Mast Repair
« Reply #1 on: April 02, 2022, 03:22:33 AM »
X-ray of a Sabfoil mast, doesn’t seem to be any inserts.

Norfolkfoiler

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Re: Mast Repair
« Reply #2 on: April 06, 2022, 01:18:42 AM »
That is super helpful. So I assume this is a solid piece of brass, with the threads for the fuse bolts tapped into the ‘ears’ on the left and right of this image. So when the ‘insert’ fails, it will be one of the ‘ears’ that is has broken off..

Anyone got any ideas on how to repair this?


finbox

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Re: Mast Repair
« Reply #3 on: April 06, 2022, 07:59:01 AM »
Can you post photos of the damaged Mast?

PonoBill

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Re: Mast Repair
« Reply #4 on: April 06, 2022, 10:44:35 AM »
Yes, the repair I did to an Axis carbon mast was probably similar. Basically, I ground the area around the break down a bit to allow space to wrap the area with carbon, then I used scissors to chop up some scrap carbon fiber and pulled the weave apart so I got a pile of 1/2" fibers which I turned into putty with some epoxy. Wrapped the area with some stiff mylar and filled the mold thus created with the putty and let it kick. When it was good and hard I took off the mold, sanded the repair smooth, and cleaned up any contour issues, making sure I had about an inch of wrapping area on the undamaged part. Wrapped the end with three layers of carbon, covered it with saran wrap, and jammed the fuselage on. pounding it firmly into place. I also lubed the fuselage liberally with tefgel (it was handy and nothing sticks to it) in case the saran wrap failed. After the repair set hard, I knocked the fuselage off the mast and drilled the cross hole for the insert, and the hole that intersects it for the fuselage bolt. The surface of the mast has a slight taper, so it's a bit of a challenge to get the insert hole aligned perfectly. Mine was a little off, so I decided to re-fill the hole to do it again and re-wrap the entire end of the mast. That was a PITA, if I'd been a little more careful with the cross-drilling I wouldn't have had to do it.

Incidentally, you don't have to put the insert at the same depth as the original placement. You can make the repair simpler by setting it deeper, using a longer bolt, and then doing the repair to the broken area in a non-structural way. I did this to a friend's mast, and I think it worked better. I set the fuselage in place when I drilled the hole for the bolt to use the hole in the fuselage and the remains of the original bolt hole as a drill guide. I wrapped the shank of the drill with aluminum tape in the area that touched the fuselage hole to reduce any chance of cutting into the fuselage. I did all the drilling for the insert first, then repaired the broken section with a piece of Teflon tubing stuck in the bolt hole while I did the repair with just carbon putty and molded it with the fuselage. Pulled that out and cleaned up the hole with the right size drill and done.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

Wingfoil2001

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Re: Mast Repair
« Reply #5 on: April 06, 2022, 02:16:52 PM »
Can you post photos of the damaged Mast?
I found this picture on another thread, I didn’t do the repair myself. If an ear has broken off you may be able to replace it with a side mounted barrel nut.

Norfolkfoiler

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Re: Mast Repair
« Reply #6 on: April 07, 2022, 03:26:05 PM »
Thanks ponobill for the detailed answer - I like your 2 stage approach.

Pics attached - the big question is the extent of the damage on the front insert... and how far the fracture runs for.

PonoBill

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Re: Mast Repair
« Reply #7 on: April 07, 2022, 08:46:05 PM »
Ooof, that's pretty ugly. I think I could fix that, but it wouldn't be pretty.
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

jondrums

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Re: Mast Repair
« Reply #8 on: April 08, 2022, 11:11:29 AM »
Have you talked to Sabfoil?  I would hope that even if they don't replace it free, they might be willing to replace it at cost.  If I'm Sabfoil, I would want that mast back for root cause analysis to make future products better - AND to keep customers happy.

Norfolkfoiler

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Re: Mast Repair
« Reply #9 on: April 08, 2022, 12:54:47 PM »
It’s a good suggestion - bought this mast in Dec 2020, so it is 16 months old. Will try.

Norfolkfoiler

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Re: Mast Repair
« Reply #10 on: April 13, 2022, 10:29:54 PM »
No joy from SAB - they say this happens only when then bolts are loose..

Vancouver_foiler

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Re: Mast Repair
« Reply #11 on: April 17, 2022, 08:41:21 PM »
Yes, the repair I did to an Axis carbon mast was probably similar. Basically, I ground the area around the break down a bit to allow space to wrap the area with carbon, then I used scissors to chop up some scrap carbon fiber and pulled the weave apart so I got a pile of 1/2" fibers which I turned into putty with some epoxy. Wrapped the area with some stiff mylar and filled the mold thus created with the putty and let it kick. When it was good and hard I took off the mold, sanded the repair smooth, and cleaned up any contour issues, making sure I had about an inch of wrapping area on the undamaged part. Wrapped the end with three layers of carbon, covered it with saran wrap, and jammed the fuselage on. pounding it firmly into place. I also lubed the fuselage liberally with tefgel (it was handy and nothing sticks to it) in case the saran wrap failed. After the repair set hard, I knocked the fuselage off the mast and drilled the cross hole for the insert, and the hole that intersects it for the fuselage bolt. The surface of the mast has a slight taper, so it's a bit of a challenge to get the insert hole aligned perfectly. Mine was a little off, so I decided to re-fill the hole to do it again and re-wrap the entire end of the mast. That was a PITA, if I'd been a little more careful with the cross-drilling I wouldn't have had to do it.

Incidentally, you don't have to put the insert at the same depth as the original placement. You can make the repair simpler by setting it deeper, using a longer bolt, and then doing the repair to the broken area in a non-structural way. I did this to a friend's mast, and I think it worked better. I set the fuselage in place when I drilled the hole for the bolt to use the hole in the fuselage and the remains of the original bolt hole as a drill guide. I wrapped the shank of the drill with aluminum tape in the area that touched the fuselage hole to reduce any chance of cutting into the fuselage. I did all the drilling for the insert first, then repaired the broken section with a piece of Teflon tubing stuck in the bolt hole while I did the repair with just carbon putty and molded it with the fuselage. Pulled that out and cleaned up the hole with the right size drill and done.

+1 with that Bill. I've both fixed and customized carbon mast's setting a barell nut deeper than factory. Much stronger really.

surfcowboy

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Re: Mast Repair
« Reply #12 on: April 29, 2022, 07:44:44 AM »
A note on loose bolts. Use tefgel or something like Teflon tape (a buddy does that) to give some stick so bolts don't loosen. Even if you don't need it for corrosion protection it helps them not back out I've found.

Loose bolts will break the bolt or something when a shock hits them. Sorry that happened man.

Norfolkfoiler

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Re: Mast Repair
« Reply #13 on: May 03, 2022, 01:03:47 PM »
Took a bunch of work, but got a useable 60cm mast from my broken 82. Time will tell how strong it is.

Chopped the mast down to 60cm (aim is a mast for teaching my daughter)
Cut out the plywood core to a depth of 50mm
Filled with epoxy mixed with carbon powder
Made a jig to get the position of the mast relative to fuselage
Cast the new head in place using wax release agent in the fuse
Wrapped the base of the mast in 4 layers of carbon weave
Drilled/cross drilled for the new dowel nuts (managed to find some stainless ones on ebay)

A good number if mistakes along the way, but nice thing with carbon is you can refill and go again.

Thanks ponobill for the advice.


surfcowboy

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Re: Mast Repair
« Reply #14 on: May 03, 2022, 07:52:29 PM »
Nice work! That's a tough one to do well.

 


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