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Do I need to repair gel coat?
http://www.hobie.com/au/en/forums/viewtopic.php?f=14&t=56848		 Page 1 of 2
Author:  fobos8 [ Fri Feb 05, 2016 1:30 pm ]
Post subject:  Do I need to repair gel coat?
Hi all

The underside of my hulls right at the very bottom have the gel coat worn off completely and you can see the glass fibre. Before I dive in and repair the gel coat is it really necessary? No one ever sees it. Will there be any problems from not repairing the hull's gel coat?

Regards, Andrew
Author:  bmdumr [ Fri Feb 05, 2016 3:44 pm ]
Post subject:  Re: Do I need to repair gel coat?
fobos8 wrote:
Hi all

The underside of my hulls right at the very bottom have the gel coat worn off completely and you can see the glass fibre. Before I dive in and repair the gel coat is it really necessary? No one ever sees it. Will there be any problems from not repairing the hull's gel coat?

Regards, Andrew

This is the classic "bottom job". You can search for tons of information here and on the internet. Depending on how badly worn they are depends on the level of work required. Mine were worn badly when I bought my '84, so I layed up 3 layers of 2" wide fiberglass cloth strips with bondo brand polyester fiberglass resin. Others will insist on using epoxy. My understanding is that polyester is used in the orginal construction, so I chose poly. Then I sanded it all to the stock profile, filled any little voids, primed and rattle canned the repair area with gloss white. I think it turned out pretty great. Like you said, it's the bottom, so it's more about function than aesthetics.
Author:  fobos8 [ Sat Feb 06, 2016 2:20 am ]
Post subject:  Re: Do I need to repair gel coat?
bmdumr - when you worked on your hulls I'm assuming you flipped the cat over to work on it. What did you support it on? Will some car tyres be okay for about a month?

Regards, Andrew
Author:  bmdumr [ Sat Feb 06, 2016 9:35 am ]
Post subject:  Re: Do I need to repair gel coat?
fobos8 wrote:
bmdumr - when you worked on your hulls I'm assuming you flipped the cat over to work on it. What did you support it on? Will some car tyres be okay for about a month?

Regards, Andrew

I didn't remove my hulls from the frame, so I simply put plastic work horses under the aluminum side rail. I just propped one side up a time. I went back to look at my pictures of it and it also looks like I just set it on the ground upside down. A lot of people store hobies on used tires so I'm sure that's fine.

I put my bottom job photos in an imgur album here: http://imgur.com/a/kskkw

Btw, the photos are completely out of order. Not sure why.
Author:  fobos8 [ Sun Feb 07, 2016 2:06 am ]
Post subject:  Re: Do I need to repair gel coat?
cheers- gonna flip it and stick some timbers under the alu frame
Author:  cpnsoo [ Sun Feb 14, 2016 12:47 pm ]
Post subject:  Re: Do I need to repair gel coat?
If you can see the fiberglass cloth layer you are getting pretty thin on the keels. As far as propping the boat up, I 've used some large wooden blocks about 18" tall under the frame. You'll want to remove the tramp so you can walk around inside the frame. Then you're at a good working height. Gelcoat would be the preferred method of finishing as it's more durable than a layer of paint. If you're planning on hitting sandy beaches, I would think that paint wouldn't last very long. You don't want to use epoxy resin at all. Don't know who would recommend it.
Author:  bmdumr [ Sun Feb 21, 2016 11:35 am ]
Post subject:  Re: Do I need to repair gel coat?
cpnsoo wrote:
If you can see the fiberglass cloth layer you are getting pretty thin on the keels. As far as propping the boat up, I 've used some large wooden blocks about 18" tall under the frame. You'll want to remove the tramp so you can walk around inside the frame. Then you're at a good working height. Gelcoat would be the preferred method of finishing as it's more durable than a layer of paint. If you're planning on hitting sandy beaches, I would think that paint wouldn't last very long. You don't want to use epoxy resin at all. Don't know who would recommend it.
You're right, I should have used gel coat... on that matter does anyone know exactly what brand and/or tint white will match Hobie 16 white hulls.
Author:  cpnsoo [ Wed Feb 24, 2016 2:15 am ]
Post subject:  Re: Do I need to repair gel coat?
I have been buying gelcoat from a company called fibre glast, out of Ohio. You can buy online. They offer a lot of colors. They even have different shades of white available. They seem to have 20% off sales every 3 months or so. They also sell Dura tech gloss which acts as a thinner, so it's easier to spray the gelcoat. With the additive you can get by without adding wax to the gelcoat.
With hobies all you do is try to match up a color. I purchased a tinted white over regular bright white for a '83. Someone had steered me to a place out of Florida, but they were highway robbery when compared to this company. I can buy gallons for the price of quarts at the other place. So I have changed the hull colors on some white boats, leaving the decks white.
Author:  fobos8 [ Wed Mar 09, 2016 2:17 pm ]
Post subject:  Re: Do I need to repair gel coat?
I have tried to apply some gelcoat. It was a disaster. I sanded the area, cleaned up with some Tetrosyl thinners and then applied the gel coat. The next day I went to sand it and could pick it off with my fingernails. It hadn't bonded to the fibreglass.

I've no idea why... I check I added the correct amount of catalyst.

The boat of made from glass fibre and polyester resin. The get coat is polyester based too so what is going on?

Anyone got any ideas? Cheers, Andrew
Author:  cpnsoo [ Wed Mar 09, 2016 4:08 pm ]
Post subject:  Re: Do I need to repair gel coat?
You want to use acetone to clean the are before applying gelcoat.
Temperature should be around 70 degrees for best results, cold temps and gelcoat may not harden up right.
Sand area with 240 grit or less for a good bond.
Author:  srm [ Wed Mar 09, 2016 6:34 pm ]
Post subject:  Re: Do I need to repair gel coat?
Not sure about the Tetrosyl thinner. Acetone is what you want to use to clean the surface. Sand the area down using 100 to 150 grit sand paper. Also, the gelcoat needs to be covered or have wax mixed in to fully cure. You can either get gelcoat with the wax already mixed in, or you can get liquid styrene wax and mix a few drops in when you add the catalyst to the gelcoat. Otherwise, it should work the same as regular polyester resin.

sm
Author:  mdgann [ Thu Mar 10, 2016 12:45 pm ]
Post subject:  Re: Do I need to repair gel coat?
Just finishing up this exact process. You probably will not be able to get the thickness you want with only 1 coat of gel coat so you need to use the raw stuff without the wax so that it will stay tacky and bond well with the next layer. I put on 6 layers and got about 0.030in thickness. You will then need to wet sand about 0.003-0.005in off to get it all even and smooth. You don't want to put it on too thick as it will wrinkle when it sets up. I brushed on the first 2 coats and it was coming out great, then made the mistake of trying to roll it on with a smooth 3 inch roller. It does not self-level so all the dimples and orange peel stayed in. It took 3 more brushed on coats to even it all out again. The last coat is the only coat that I added the wax so that it would set hard and sandable. It worked great. I have finished the rough sanding and hope to finish the wet 600 grit this Friday. Some people go to 1000 grit, but this is the bottom ridge of my hulls. No one is ever going to see down there. Plus I will be doing this again in a few years. I'm a sailor, not a maintenance worker. If you need more details, contact me through the forum or mention in here and I will get you my personal email. Have a Hobie day.
Author:  fobos8 [ Sun Mar 20, 2016 4:28 am ]
Post subject:  Re: Do I need to repair gel coat?
Many thanks for taking the time to reply guys but unfortunately its still not going well. 24 hours after applying the gel coat I can pick it off quite easily with the end of a paint scraper. The gelcoat is setting up nice but not bonding too well. This is my process;

1) Mask off area
2) Sand with 120 grit
3) Clean with acetone
4) Mix up gelcoat (proportions are 20ml hardener per 1kg - I'm actually mixing 1.25ml with 62.5g). Gelcoat already has wax in it.
5) Apply gelcoat - I'm doing this quite thickly about 2mm or 3/32 of an inch.
6) Leave for 24 hours
7) Cry because gelcoat can be picked off! :cry:

Possible reasons why this isn't working;

1) I'm using waxed paper cups for mixing. Is this contaminating the gelcoat? Will use plastic next time.
2) I opened the inspection holes and found about a pint of seawater in each one. I imagine its been in there for about a year. Could moisture have got through to the outer layers of the hulls and prevented adhesion. Have now got out all the water, the inspection caps are off and the boat is in the garage.

Anyone like to chime in with some thoughts?

Best regards, Andrew
Author:  cpnsoo [ Sun Mar 20, 2016 8:32 am ]
Post subject:  Re: Do I need to repair gel coat?
I once tried to use a gelcoat puddy to fill deep scratches and had problems with it hardening due to low temperature.
What kind of temperature are you working under?
I find regular gelcoat to work best over 70 degrees F. It should set up in hours. Sounds like the temperature may be too cold. Catalyst should be adjusted for temperature.
Author:  thejacksonfour [ Wed Dec 01, 2021 1:26 pm ]
Post subject:  Re: Do I need to repair gel coat?
With all due respect to the fantastic replies, I do not think the original question has been answered. I believe the question was "is it ok to NOT do a bottom job"... any answers on that? I too have worn gelcoat but no fiberglass wear and I am wondering how long I can/should go without putting in the work. thoughts? Thanks much all.
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