Failed soft spot repair :: Catamaran Sailboats at TheBeachcats.com

Failed soft spot repair

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waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Jul 11, 2021 - 02:33 PM

Hey all,
We did the Hobie resin injection procedure but with poor results. Any advice? I'm tempted to cut a batch out of the top panel, rebond the foam below, bond the top back on and add a few plies.

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
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raisehull

Rank: Lubber

Registered: Jul 11, 2014

Last visit: Mar 18, 2024

Posts: 80
Posted: Jul 11, 2021 - 03:04 PM

Several questions for you, as I am preparing a similar repair. 1) How big an area are you trying to repair? 2) What was the spacing of your injection holes. 3) Did you inject one hole until it oozed out the neighboring holes,then tape those holes off? 4) What epoxy were you using? 5) just how soft was the area? 6) what do you think lead to the poor results? Thanks in advance.

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1978 H18
1983 H18 (some of it)
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waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Jul 11, 2021 - 06:42 PM

raisehullSeveral questions for you, as I am preparing a similar repair. 1) How big an area are you trying to repair? 2) What was the spacing of your injection holes. 3) Did you inject one hole until it oozed out the neighboring holes,then tape those holes off? 4) What epoxy were you using? 5) just how soft was the area? 6) what do you think lead to the poor results? Thanks in advance.

1) I'll post some pictures and you can see.
2) About 4".

3) I was not getting oozing in the neighboring holes, so I just injected as best I could in all of them
4) System 3 like this: https://www.amazon.com/gp…asin_title?ie=UTF8&psc=1
5) It seemed pretty soft. Not sure how to put a measure on it.
6) The foam was wet!

I decided to cut out a panel on the top. I practiced on a scrap from the old boat. That is a circle/straight line cutter tool for the dremel. Shown is circle mode. It uses a little router/cutter bit.

Here is the straight cut after I did the two half circle cuts on my hull.

Top popped off. The foam was wet!

We heated up the inside of the boat. Our hangar thermometer was removed from the wall and put in the hull. It read 120F after 10 minutes or so.

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
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raisehull

Rank: Lubber

Registered: Jul 11, 2014

Last visit: Mar 18, 2024

Posts: 80
Posted: Jul 12, 2021 - 03:58 PM

I think they recommend the holes a little closer together but, if you got moisture, it prob good you opened it up. Looks like dremel makes you buy 2 of those adapter tools.

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1978 H18
1983 H18 (some of it)
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waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Jul 12, 2021 - 04:18 PM

I didn't see any spacing here:
https://www.hobie.com/for…iewtopic.php?f=18&t=1156

This is the bit I bought at Lowes. Came in a single pack.
https://www.amazon.com/Dr…it&qid=1626120991&sr=8-3

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
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raisehull

Rank: Lubber

Registered: Jul 11, 2014

Last visit: Mar 18, 2024

Posts: 80
Posted: Jul 12, 2021 - 04:39 PM

ok, but i mean that radius adapter for the dremel.

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1978 H18
1983 H18 (some of it)
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waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Jul 12, 2021 - 08:01 PM

raisehullok, but i mean that radius adapter for the dremel.

I bought mine 6 years ago at Lowe's Depot or somewhere local. You can still get them on eBay.
https://www.ebay.com/itm/…&mkrid=711-127632-2357-0

Also I agree that with the wet foam it had no chance to bond.

Edited by waiex191 on Jul 12, 2021 - 08:02 PM.

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
--
raisehull

Rank: Lubber

Registered: Jul 11, 2014

Last visit: Mar 18, 2024

Posts: 80
Posted: Jul 13, 2021 - 08:42 AM

If I wasn't so busy, I would ask to come down there and see what yer doin. I am about an hour's bike ride North east of you.

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1978 H18
1983 H18 (some of it)
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waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Jul 13, 2021 - 09:09 AM

raisehullIf I wasn't so busy, I would ask to come down there and see what yer doin. I am about an hour's bike ride North east of you.

I'll take lots of pictures. You are welcome to visit but this is a bad week - customer meetings and I actually have to go into work. What do you ride? I took my '89 FJ1200 in today.

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
--
waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Jul 13, 2021 - 11:04 PM

I decided to use the hatch I cut out as the backup to close the hole I cut. It was more or less the right shape & size, plus it had some curve to it. I sanded off the gelcoat first. The things holding it in are clecoes, which we also use to build/repair airplanes.

I beveled off the edge of the cut and the foam. I used a right angle sander to do this initially, and finished up with a piece of 60 grit.

This is after bonding that part in. I made little duct tape handles to pull it into place. It is thin and floppy. Because I was impatient, I used 5 minute epoxy for this part.

There are a couple of plies on that first patch from the prior pictures, to make it all sort of the same level. Then I glassed in two plies, one on a 45 bias and one straight.

Next up: I need to bond in foam. Hope to get it higher than the deck and then sand it level with the deck. Then a couple of plies on top. Because we don't belong to the yacht club, I am not going to try and hide this patch.

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
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waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Jul 14, 2021 - 07:46 PM

Check out the latest at Joyrider TV! Hull repair:
https://youtu.be/FCp_5_kfBiM

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
--
waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Aug 01, 2021 - 09:26 AM

I've been away for a couple of weeks. First visiting family, then Oshkosh 21. I'm back.

There were low spots in the repair above, where the big oval hole was. So, I made some flox out of sawdust & resin and filled it in a bit.

Next, I've sanded it down.

I think it's good enough. I took some of my harvested foam core from the failed hull and bonded pieces together to get one about the right shape. I just used 5 minute epoxy on the edges. I trimmed/sanded the edges to make them square and flat. To transfer the shape from the hull to the foam, I used a sharpie to mark around the perimeter. Next I taped a leftover piece of 1.5 oz white ripstop nylon in place so I could transfer the sharpie marks and cut out the shape. Sort of hard to see the white translucent-ish nylon on the white hull, but that is what is going on here.

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
--
waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Aug 01, 2021 - 07:50 PM

I finished shaping the foam, then bonded it in. I did a redneck vacuum bag setup.

I used a garbage bag, some silver HVAC type duct tape, and an old towel for the breather, and a Harbor Freight car AC vacuum pump.

I used nylon tubing to go from the bag to the vacuum pump. Quarter inch OD will just jam into one of the AC fittings. On the bag side, I jammed it through the bag and taped it up. I also taped a piece of towel over the end to let it breathe. It has been curing for a few hours, and I'll go over and pull off the pump tonight. I have to leave the pump run outside the garage door as it generates an oil mist when it is running.

Cheap and redneck but it is getting the job done.

We also moved the tramp from the old frame to the current boat, since I had sewed new hiking straps onto that tramp. Plus I bought some neoprene for the rail. I bought a SUP/surfboard sheet with 3M adhesive.
https://www.hydroturf.com…-heavy-brush-sht23f-psa/

Murrays gets $65 for a Hobie 16 kit. This is the same manufacturer, slightly different style (flat rubber vs bumps) and is $70 for two boats worth - or one boat 2X.

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
--
waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Aug 01, 2021 - 10:22 PM

After it cured for 5 hours, I went and pulled off the vacuum pump and bag. Here you can see the somewhat squished old towel that I used for a breather.

The repair is coming out good. I have to sand it next, then glass the top.

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
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charlescarlis

Rank: Mate

Registered: Jun 30, 2018

Last visit: Nov 21, 2024

Posts: 593
Posted: Aug 02, 2021 - 09:18 PM

Hey, questions: 1) did you think of bonding the top layer of glass and the foam all at once? Kind of like a toxic taco... I end up using a thick mylar as a release film, but that leaves a slick finish. 2) How did the a/c tape work as a seal? That's where I usually fight leaks the most. I've built a vacuum pump with an old helium tank for balloons as a reservoir and an on/off switch to work just like a compressor, but in revers so the pump hardly runs, if you're interested. Was WAY cheaper than I thought.

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Chuck C
NACRA 500 Mk2
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waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Aug 02, 2021 - 10:10 PM

Chuck, my foam was imperfect. In order to blend in with society I have to make mistakes so nobody realizes I'm actually a terminator. So the foam stuck up around the edges and was in general a little too thick. With it bonded down, I was able to sand it and get it pretty good:

Note my sanding block is actually a piece of Hobie skin from the failed hull. It is flexible so I can follow the contour. It isn't perfect but I think good enough. I will probably flox a couple of edge gaps that are there, and whip some layers of glass on top. Perfect is the enemy of good enough.

At Sikorsky we used to do like you say - except everything was carbon prepreg, we had CNC machined molds, and CNC machined foam or Nomex core. We would pull the prepreg carbon out of the freezer, let it thaw a little, place parts in the mold, vacuum bag it, then stick it in the pressurized autoclave.

If I was going to vacuum bag glass I'd break down and buy some peel ply. That does a couple of things -
1) leaves the finish with a textured surface, suitable for bonding to
2) soaks up the excess resin

That silver AC tape is old but works good enough. We had one leak on the tape but just kept adding more until it went away.

Clever idea, making an inverse air compressor!

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
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Edchris177

Rank: Chief

Registered: Nov 26, 2009

Last visit: Aug 10, 2024

Posts: 2531
Posted: Aug 03, 2021 - 08:06 AM

I like your ideas & the perseverance you’ve put into your old & broken cats.
I’m sure you already know this, but after sanding those glass edges, be sure to wipe a thin coating of epoxy over the final sanding.
It seals those fine fibres in the glass, which have a nasty habit of getting embedded in water softened human skin!

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Hobie 18 Magnum
Dart 15
Mystere 6.0XL Sold Was a handful solo
Nacra 5.7
Nacra 5.0
Bombardier Invitation (Now officially DEAD)
Various other Dock cluttering WaterCrap
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waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Aug 03, 2021 - 08:36 AM

Great idea to seal with epoxy. The previous owner had painted the boat with rustoleum marine paint. I wonder if that will also seal them? We bought a quart to make the repair match.
https://www.amazon.com/Ru…nt&qid=1627994119&sr=8-5

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
--
waiex191

Rank: Mate

Registered: Oct 07, 2020

Last visit: Feb 29, 2024

Posts: 359
Posted: Aug 04, 2021 - 12:39 AM

I put 3 plies on top. Two cut square and one cut on a 45 bias.

Edited by waiex191 on Aug 04, 2021 - 09:18 AM.

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Bryan in Poplar Grove, IL
Supercat 17, unknown year. Future project
Hobie 16, 1977 - died a spectacular death https://youtu.be/Y7O22bp2MVA
Hobie 16, 1978 - current boat
--
MN3

Rank: Master Chief

Registered: Jun 20, 2006

Last visit: May 22, 2024

Posts: 7089
Posted: Aug 04, 2021 - 09:34 AM

It's gonna be the strongest part of the boat for sure!~