Author Topic: Mast cracks  (Read 7138 times)

p06781

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Mast cracks
« on: November 04, 2019, 09:24:39 PM »
Hey I bought this mast off another member fully knowing it had issues.  I got a great price to use it as a learning rig for surfing. The mast has hairline cracks and was wondering what you guys thought the best way to repair was? Go foil does address this issue and says to sand and apply epoxy.  Just throwing it out for ideas? It seems very solid yet ?

Jim in pdx

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Dwight (DW)

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Re: Mast cracks
« Reply #1 on: November 05, 2019, 02:41:16 AM »
The cracks GoFoil talks about as normal, are the fillet radius cracks from filler. They are harmless.

The cracks you have, look to be structural delamination from flexing. While the mast might feel fine, Im sure its lost stiffness and complete failure is coming. Id wrap carbon around that area. If you watch the Axis 2020 product video featuring Adrian Roper, he talks about how all the flex in a mast comes right at that spot where yours is failing. This is why they made their carbon mast super thick right in that zone. So go for it. Wrap it in carbon. It wont cause drag way up there.


PonoBill

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Re: Mast cracks
« Reply #2 on: November 05, 2019, 07:40:51 AM »
^^What DW said. Those are serious cracks. I've never seen that on a gofoil mast but I'd be wrapping the heck out of that one. Sand all the paint off befor you add the carbon, or have someone do it that knows composite repair. It's savable, but only if it's done right.
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p06781

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Re: Mast cracks
« Reply #3 on: November 05, 2019, 09:41:36 AM »
Thanks guys ! Yes I was considering wrapping it ! Do you think standard glass will do or buy some carbon?  Yes will sand all the paint off before reinforcing it !

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Bean

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Re: Mast cracks
« Reply #4 on: November 05, 2019, 10:40:15 AM »
For a really clean and easy repair you might consider using carbon sleeves and heat shrink tubing.  Once cured, the shrink tube zips right off leaving a very clean surface.

https://www.sollercomposites.com/CarbonSleeves.html

https://www.sollercomposites.com/ShrinkTubing.html

PonoBill

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Re: Mast cracks
« Reply #5 on: November 05, 2019, 11:26:11 AM »
Get some carbon. Enough for a few layers extending at least a few inches past the end of the cracks. In some ways, this would be a good place to use tow instead of woven fabric, and I might give that a go, though you'd have to do something like lay a bunch of short pieces vertically before you wrapped horizontally to improve the strength in both directions. I doubt you'd really be able to get a carbon sleeve to make the turn and lay flat on the trailing edge even with shrink tubing, the leading edge will be hard enough. I've never seen the cross-section of a GoFoil mast, but I bet the leading and trailing edges are already pretty thick. If I didn't have vacuum bagging gear I'd probably try mylar wrapping full-width patches.

Use coarse paper, like 60 grit to leave some mechanical grip, stand it up vertically in a vise and wet the surface with epoxy and slow hardener and lay on two or three layers of prewet carbon on each side. I wouldn't try to wrap it over the edges, especially after all the fussing I had to do to make the Fatboy foil, just cut the carbon short of the edges. Take apart an old VHS tape to get the reel of Mylar. Do a few wraps to hold the patches down, then wrap tightly, overlapping about half the width of the tape on each wrap. It will probably be a messy bitch to do, but the pressure of the tight mylar will bond it about as well as vacuum bagging. After the epoxy is fully set the Mylar comes off easily. A lot of the paddle shafts and carbon tubes are made with mylar wraps over a tapered mandrel.

You might get away with just laying big patches on with nothing to improve the mechanical bond, but you're aiming for strength, not just for covering, so I'd go for what I could get. DW might have a better idea.
Ponohouse is for sale: http://www.ponohouse.com
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.

Beasho

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Re: Mast cracks
« Reply #6 on: November 06, 2019, 06:10:52 AM »
Thanks guys ! Yes I was considering wrapping it ! Do you think standard glass will do or buy some carbon?  Yes will sand all the paint off before reinforcing it !
 

Use CARBON.

The modulus of Carbon and Glass are different meaning they stretch at different rates.  There is no point in using stretchy Glass with Carbon because one half will carry the load and fail before the other kicks in.  It may NOT matter on something that isn't bending (aka stiff mast vs bendy paddle shaft) but to what DW and PonoBill are saying just do it right and with a little over-touch and you should be able to fix that Mast. 

I have fixed several broken paddles using the method that Ponobill suggests here and they have NEVER failed twice. 

The ironic thing is the direction of the cracks.  It suggests torsional or buckle failure.  The good news is IF it was a buckle situation a solid patch will address the problem well.

PonoBill

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Re: Mast cracks
« Reply #7 on: November 06, 2019, 06:43:58 AM »

The ironic thing is the direction of the cracks.  It suggests torsional or a buckle failure.  The good news is IF it was a buckle situation a solid patch will address the problem well.

Probably torsion, I'd expect to see some kind of crease from a buckle failure or splitting along the leading or trailing edges, though that crack between the 9 and 3 of the patent number looks very suspicious. With the load required to crack the mast in multiple places, a buckle seems likely to result in two pieces. In either case, a good patch would fix it, and I agree, fiberglass won't fix this unless it's half an inch thick.

I need to look that patent up, it's got to be very narrow. WTF is patentable on something that's been around for a hundred years?
« Last Edit: November 06, 2019, 06:49:32 AM by PonoBill »
Ponohouse is for sale: http://www.ponohouse.com
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.

Bean

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Re: Mast cracks
« Reply #8 on: November 08, 2019, 07:02:48 AM »
The chipping on both sides of the cracks could also indicate that the mast was crushed.  My best guess would be that it was run over by a 1963 Pontiac Tempest (yes, with posi-traction). ;)

PonoBill

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Re: Mast cracks
« Reply #9 on: November 08, 2019, 08:57:40 AM »
is that posted in your best Marisa Tomei voice?? Can I be Joe Pesci??
Ponohouse is for sale: http://www.ponohouse.com
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.

Bean

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Re: Mast cracks
« Reply #10 on: November 08, 2019, 09:38:21 AM »
Right on Bill!

kiwi

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Re: Mast cracks
« Reply #11 on: November 08, 2019, 09:56:25 AM »
I would scallop out the surface with a grinder and probably get rid of all the paint in that area to see how deep the damage goes and then lay a combination of unis and double bias carbon in there and also over the whole chord of the mast.
As DW said the axis cabon mast is super fat up there so feel free to keep adding cloth and fatten it up.

jondrums

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Re: Mast cracks
« Reply #12 on: November 08, 2019, 10:27:54 AM »
This used to be mine - I basically gave it to him and charged him a little for some wings.  It was not run over by a car or crushed.  My best guess is torsion overload.  I break most sports equipment I use.  Though I haven't seen anything like it in the other two gofoil masts I've ridden quite a bit more.  The other possibility since this mast was from the very first production run of gofoil is that maybe they have updated the layup schedule since then.

Seems like most stuff is tested by 150lb sporty 20 year olds.  Loads don't go up linearly with rider weight.  I used to have the same problem with windsurfing gear, it got expensive.  Steamroller probably knows what I'm talking about - we have a similar style.

PonoBill

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Re: Mast cracks
« Reply #13 on: November 08, 2019, 10:52:13 AM »
I know very well what you're talking about. Now I'm down to a svelte (not!) 235 but for most of my windsurfing decades I was 250+. And I liked togo fast and jump. Bad combo. I broke things that I don't think anyone else broke. Chinook booms, ampro masts. I went straight through two boards on landing--a Lanny Shuler and a Naish. I'm still a little hard on gear. For downwinding, everyone at the SIC shop in Maui yelled NO! in chorus when I said I wanted a lightweight Bullet 17 V2. Just because I knee-dropped a few holes through the deck of a carbon-kevlar V1.  Admin says my wings look like a hobo's hanky.

I know a lot about fixing stuff. It's not because of intellectual curiosity.

So yeah, Nobody wants my used shit.
Ponohouse is for sale: http://www.ponohouse.com
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.

p06781

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Re: Mast cracks
« Reply #14 on: November 13, 2019, 07:17:31 PM »
Ok put 6 layers of directional carbon down alternating directions on each side . I also opened up the cracks and injected epoxy everywhere I could get a small needle into before adding the outside carbon. I ended just clamping with some foam and boards.  It looks solid as hell now. 

Will finish sand it and put on a finish coat then maybe paint to cover up my duck tape repair.

Thanks for the help .

Any thoughts on the fuselage since I have all my epoxy crap out ?

James

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