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 Post subject: Hobie 17 hull repair
PostPosted: Tue Dec 15, 2009 3:41 pm 
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Site Rank - Deck Hand

Joined: Thu Dec 03, 2009 11:47 am
Posts: 9
I just purchased a Hobie 17 and there is a crack on the bottom of the port hull where it was sitting on the forward roller. I plan to make the repair myself, but have little experience working with fiberglass, so am looking for some advise. I couldn't figure out how to post the photos in this topic, so added them to my website at http://pages.suddenlink.net/bobmcreynold. Just click on the 'Hobie 17' link.

The 1st big question is should I cut the entire area where the crack is and completely re-glass it? Other option would be to grind down the area from the outside, add new glass and cloth, and then do the same thing on the inside? This eliminated the need for a form, but maybe it wouldn't be as strong? Since the crack goes from one side of the bottom to the other, I was thinking the 'cut a hole' would be best.

If I do cut the hole, what is the best way to make a form, so the glass can be layed down inside the hull and keep the hull shape? I was thinking about purchasing a low density foam sheet Home Depot, heat it so it can be shaped to the hull, screw it down just outside the hole, glass the inside part 1st, cut the foam away on the outside of the hull, and glass the outside. Sure sounds simple, but......

I was planning on using West System epoxy. All information about this repair would be very helpful!
Thanks,
Bob
rwmcreynolds@yahoo.com


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 Post subject: Re: Hobie 17 hull repair
PostPosted: Tue Dec 15, 2009 9:57 pm 
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Hobie Approved Guru

Joined: Mon Jul 14, 2003 7:11 pm
Posts: 4642
Location: Detroit, MI
Read the "This Old Hobie" article in this issue of the HOTLINE:
http://www.hobiecat.com/hobieclass/eHCA_News03-04_2008.pdf


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 Post subject: Re: Hobie 17 hull repair
PostPosted: Thu Dec 17, 2009 7:59 am 
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Joined: Thu Dec 03, 2009 11:47 am
Posts: 9
That article was exactly what I needed. Thanks!

My repair should be almost the same size. How much resin and cloth should I purchase? I was planning to use West System products.

I have a 4 1/2" high speed grinder. What grit (40, 80, 120) sanding disc should I purchase to sand off the gel coat and other fiberglass? I understand a fine grit sandpaper is used for the finishing work.

Does the interior fiberglass need to be sanded or cut down before applying the new resin or just cleaned?

Can the resin be applied with a cheap paint brush or do I need to purchase a roller?

Will the gelcoat stick to the epoxy resin or do I need to paint the area with an acrylic epoxy?

Thanks again!
Bob
1986 H17


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 Post subject: Re: Hobie 17 hull repair
PostPosted: Thu Dec 17, 2009 8:23 am 
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Joined: Mon May 09, 2005 10:25 am
Posts: 2619
Location: Jersey Shore
Quote:
I have a 4 1/2" high speed grinder. What grit (40, 80, 120) sanding disc should I purchase to sand off the gel coat and other fiberglass?


In my experience, 80 grit paper on a sanding disk will take it down nicely. However, I would not use a high speed grinder. This will remove the material much too quickly and it will be difficult to control what you're doing. I use a variable speed electric drill and go very slowly (probably between 2 and 10 revolutions per second).

Quote:
Does the interior fiberglass need to be sanded or cut down before applying the new resin or just cleaned?


Any existing glass should be scuffed up using coarse sand paper and then cleaned using acetone prior to laminating.

Quote:
Can the resin be applied with a cheap paint brush or do I need to purchase a roller?


Personal preference really. I almost always use the cheapest brushes they sell at Home Depot. Just watch out for bristles ending up in your work.

Quote:
Will the gelcoat stick to the epoxy resin or do I need to paint the area with an acrylic epoxy?


Gelcoat will not bond well to epoxy. You can use epoxy for the repair, but if you do, you'll have to paint. You'd actually be better off using polyester or vinylester resin for the repair since that's what the boat is made from, that way you're maintaining like materials throughout the boat.

sm


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 Post subject: Re: Hobie 17 hull repair
PostPosted: Thu Dec 17, 2009 10:23 am 
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Joined: Mon Jul 14, 2003 7:11 pm
Posts: 4642
Location: Detroit, MI
srm wrote:
You'd actually be better off using polyester or vinylester resin for the repair since that's what the boat is made from, that way you're maintaining like materials throughout the boat.


That's the biggest take-away from the whole post. Epoxy is great stuff - and I wouldn't hesitate to use it on the inside of the boat - but it's expensive and you're asking for trouble if you use it on the outside.

Polyester will not adhere well to epoxy.


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 Post subject: Re: Hobie 17 hull repair
PostPosted: Thu Dec 17, 2009 6:05 pm 
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Joined: Thu Dec 03, 2009 11:47 am
Posts: 9
Thanks again for the help!


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 Post subject: Re: Hobie 17 hull repair
PostPosted: Thu Dec 17, 2009 7:40 pm 
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Joined: Sun Jun 21, 2009 7:32 am
Posts: 298
I always used West System on interior repairs that didn't project to the outside mainly because it will stick to about anything, is very strong, I never had it come off of anything I put it on, and the pump containers are very handy. Don't cut out anything that is still structurally strong enough to hold it's position. Anything that needs to be covered with gelcoat needs poly under it so on the outside that all that should be used.

http://www.fiberglasssupply.com/


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 Post subject: Re: Hobie 17 hull repair
PostPosted: Fri Dec 18, 2009 4:37 am 
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Joined: Mon May 09, 2005 10:25 am
Posts: 2619
Location: Jersey Shore
Just to offer some further information regarding epoxy vs. polyester/vinylester- this is my understanding, and I'm not a chemist...You can bond epoxy to polyester/vinylester, you can not bond polyester/vinylester to epoxy (at least not easily). Obviously you can also bond epoxy to epoxy or polyester to polyester.

So since the boat is made using polyester resin, you can do a structural repair using either polyester or epoxy. However, when it comes time to finish the repair, if you used epoxy then you can't gelocoat because gelcoat is polyester based. Also, if you use epoxy for your repair, and then sometime later down the line you have to do additional repairs to the same area, you would have to remember to use epoxy again. So it ends up being better in the long run to just keep the same material throughout the hull.

sm


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