Hole in Hull

Regarding the DS3 only. Note that the DS3 is not a class-legal Day Sailer.

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Hole in Hull

Postby jefflw » Mon Oct 27, 2008 2:02 pm

I found an impact site on the hull of my DS3. it mesaures a couple of inches, i.e. round cracking and in the center is a crack probably 5/8 inch long....I noticed as brown, rust coloring around it. I am not sure if the crack goes all the way through the fiberglass. I have not had the boat out on the water yet (although water did drain from the bilge after I purchased the boat and drove it home).

Question is how to repair this. Do I need to dig at it which would make it bigger, or is there a patch that I can apply over it.
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Postby algonquin » Mon Oct 27, 2008 3:53 pm

Does it look like a puncture from the outside of the hull ?


I would open the damaged area then use an very abrasive sand paper and sand the finish off about 3 - 4 inches or so around it and glass back over it using a fiberglass kit that contains fiberglass fibers in it. Sand smooth and spray with an appropriate color. Brad
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Postby markst95 » Tue Oct 28, 2008 12:33 am

The proper way to repair a hole in the hull is to grind a bevel out around the hole and then add circular layers of fiberglass cloth, each layer slightly larger than the last until you have filled the hole almost to the outside layer. If you use polyester resin you can then finish with gelcoat to match. If epoxy, you would fair smooth and cover with bottom paint or something with some uv protection in it. .
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Postby mainegrw » Tue Oct 28, 2008 6:18 am

You might also be able to get away with using Marine-tex, which is a putty of sorts. I used some on my DSII when I got it to fill in some cracks and dings in the gel-coat, and from what I can gather, it may be a simple solution for your problem too. Also, it comes in white, so no painting is necessary afterword.
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in addition to other good advice given already

Postby Roger » Tue Oct 28, 2008 9:29 pm

in addition to other good advice given already, I would advise the following. If the 'bruise' is below or near the waterline assume that the inside of the damage is wet. Prep as others have indicated above, but assume the area has had moisture in it. Clean the area with acetone, and put a heat lamp or heater on it for a few days to eliminate any moisture. Also assume that this impact has fractured some of the layers of fg cloth or mat beneath the gelcoat, so the repair will definately require grinding out a bevel 12 times the depth. So if the depth of the damage is 1/8" then the bevel will extend 1.5 inches from the crack in all directions... That's a 3" repair patch. Check the inside (back side of the impact crack) to determine if there is need to repair from the back side as well.

As complex as this all sounds, it really is a simple fix. Just cut a number of patches in reducing sizes from 3", and starting from the smallest patch in the base of your ground out hole, saturate it in fg resin and hardner, and start building from the bottom up. You can actually add the next patch as soon as the first has kicked. Seal the top of the last patch with the plastic lid of a margarine tub, with the outer rim cut off. This will leave a really smooth finish that needs minor sanding prior to painting. If you have gelcoat, mix up a small batch and add it to the top layer before tapeing on the margarine tub patch. You may not have to do any sanding or painting at all. (Gelcoat by the way needs an airless environment to cure, hence the margarine tub top.) A plastic sandwich bag taped in place works well on a horizontal surface, but a margarine tub works better on a vertical surface. Tape either in place with duct tape for about a half hour. If working on a horizontal surface fill the bag partially with warm water and zip seal it. This will reduce the cureing time of the fg.
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Postby jefflw » Tue Oct 28, 2008 10:21 pm

Tx for all the advice. The impact site is below the water line, actually on the bottom of the hull. I only have access to the outside so I think I will have to proceed cautiously. I havnt done anything like this before and dont want to make things worse.
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Photo of hole

Postby jefflw » Mon Nov 17, 2008 8:07 pm

Ive attached a photo of the impact site I found on the hull, below water line. I only have access to this from the exterior. The crack is approx 1 inch, maybe smaller. The camera flash highlighted a number of circular surface cracks immediately around the impact site which I had already seen, but it also highlighted more larger ones a little further out that I had not seen before. Can I get by with using Marine-tex to fix this or do I need to use fiberglass and add gel coat on top of it? I have some Marine-tex on hand but no gel coat patch kit. Should I only fix the immediate area around the impact (approx 2 1/2 to 3 inch area). Or maybe not worry about the area where cracks are on the surface and just work on the hole? I dont know If the hole goes all the way through.

671
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Postby GreenLake » Mon Nov 17, 2008 9:37 pm

Jeff,

if you just stuff MarineTex in the hole, that ought to be enough to plug any leaks - esp. if you don't leave your DS in the water between trips, where it could soak into the laminate through the cracks. However, I'd probably do more if this was my boat. Even if you decide to leave it at that, you should probably grind the repair site flat, so that you can be sure that the putty reaches everywhere (it won't flow into cracks).

From your picture, it looks like the impact was rather severe. There's got to be some strength lost in the laminate, perhaps even as far as the outer circle. Try to see if you can flex the site. If yes, then the way to get that strength back would be to grind out a generous area and rebuild the fiberglass as others have described.

BTW, you start with the first cloth the largest and use successively smaller cloths as you build up; that way, the new material doesn't meet the old material "edge" on.

Working with fiberglass isn't all that hard, esp. if you can turn the boat to where you'd be working on a level spot. It doesn't hurt, though, to do a practice run - you might mock up a dummy repair site in an old sheet of plywood. That should be enough to give you some feel for the material.

Whether you use gelcoat as the outer layer depends on whether the rest of your gelcoat is in fine shape, or whether you're better off painting the hull. In the latter case, you can work with Epoxy for your repair (less smelly and stronger). BTW, the MarineTex putty is expoxy based as well. Epoxies don't tolerate UV, so you need paint or something as a UV barrier.
~ green ~ lake ~ ~
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reverse order for cloth patches

Postby Roger » Tue Nov 18, 2008 9:24 pm

I think greenlake meant to say start with the smalles patch in the bottom of the hole and go progressively larger as you build up, to avoid edge over edge as mentioned. Otherwise you will have a lump in the middle with a lagoon around the middle distance and cloth sticking out of the edges of the hole.
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Postby GreenLake » Tue Nov 18, 2008 11:20 pm

Roger,

No, that was not a mistake. See for example http://www.westsystem.com/ewmag/21/practical.html which clearly shows the larger patch first, without commenting on it.

BTW, that site offers a nice summary of different techniques for different size holes.

I've seen an explanation for the non-intuitive approach somewhere and it goes like this: The first bond is between cured polyester and the fresh layup. That bond will be the weakest. Having the first layer of fabric flat for the whole width will give it the best strength.

I could imagine that another benefit is that you also avoid pooling resin in the stair-steps around the outside of the disks (or rather, whatever pooling you get is at the outside surface of the repair plug if its not ground away, not at the boundary to the old material).

The hole will be very shallow if you use the recommended bevel of 1 in 12. Otherwise, I couldn't imagine getting the larger patch in first, without a lot of wrinkles. However, you may well be right that "smaller first" results in a neater-looking job, or less need to grind, or both.

I could also imagine that any repair on a DS would have some strength reserve due to the rather hefty hull laminate. Therefore, I concede that Jeff's repair would ultimately be successful either way, and definitely an improvement over stuffing the crack with MarineTex :)
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Postby jefflw » Wed Nov 19, 2008 10:50 pm

Tx for the advice. Im probably going to wait until spring since my DS is outside, unless we have some warm days ahead. I assume it would be better to do this type of repair in warmer weather.

I tried flexing the area of the hull that is damaged and the flex seems consistant with other parts of the hull, so I dont think the hull is weakened. The damage is at the bottom of the hull probably 1 foot or less from the centerboard. I am hesitant to cut an access hole to reinforce from the inside, as that would mean the hole would be on the deck of the cockpit similar to the forward access holes. Roger gave me some good advice re stuffing a backer if necesary through any hole and building up from that.

Just how thick can I expect the hull to be? I dont want to grind too much and make a big hole? Also from an earlier response from markst95, it would be better for me to use polyester resin so that I can finish with gelcoat. Is there a specific fiberglass repair kit you would recommend, and a specific gelcoat repair kit too. Ive seen Evercoat Match N Patch Gelcost repair kit.

And not to get to much off the subject at hand but trying to understand the usefulness of Marine-tex ...I have what I think are just surface cracks in the gelcoat on the gunwales & foredeck that I was planning on filling with Marine-tex. There is one area on port and one on starboard where looks like something was dropped on the gunwales and lots of cracks. Probably goes all way through to fiberglass. Would it be better to use the Gelcoat repair kit on these??? If better to use Gelcoat, then what would Marine-tex be used for? NOTE: I have Marine-tex on hand but not the Gelcoat kit.
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common useage for marine tex

Postby Roger » Thu Nov 20, 2008 12:17 am

The most common usage I have seen on this and other forums (sp) for marine tex is to add a thick layer (3/4" to 1") to the leading edge of the keel, (not on our boats), as well as adding a thick 'skid plate' to the bow and centerline of a boat's hull as protection against abrasion from sand, beaching, rocks, and trailer retrieving bruises.
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Postby GreenLake » Thu Nov 20, 2008 3:07 am

jefflw wrote:I assume it would be better to do this type of repair in warmer weather.

In general, epoxies like to be worked above 65F. Probably similar for other resins.
jefflw wrote:I am hesitant to cut an access hole to reinforce from the inside, as that would mean the hole would be on the deck of the cockpit similar to the forward access holes. Roger gave me some good advice re stuffing a backer if necesary through any hole and building up from that.

Working "blind" like that should be possible.
jefflw wrote:Just how thick can I expect the hull to be? I dont want to grind too much and make a big hole?

From what I saw on your picture, I would expect that you will have an actual circular opening with a wide 12:1 bevel around it, once you are done grinding. So you will need backing. Whether you bother with beveling from both sides as the West System site suggests is up to you (probably overkill).
jefflw wrote: Also from an earlier response from markst95, it would be better for me to use polyester resin so that I can finish with gelcoat.

The West System people seem to think that gelcoat over their epoxies can be managed. (There's a test report on their main site. They give the name of some types of gelcoat they tested.) Read and follow their notes on surface preparation: de-grease and de-wax your repair before grinding (and again when you are done). Clean off any amine blushes from epoxy after it cures before you do the next layer of whaterver, etc.

I've used pre-tinted gelcoat repair kits that were matched to a line of powerboats - just picked the closest color I could find. I've also used a clear gelcoat repair material, for spots where the underlying gelcoat was good enough to give color. (Sorry don't remember the brands - for gelcoats make sure you cover the outside with some waxpaper, or plastic sheet to make sure the oxygen in the air doesn't prevent it from curing - some will have wax suspended in the mix to make that unnecessary, but better safe than forever tacky).

For fiberglass layup I've used SystemThree. They produce a very nice range of epoxies for marine use (SilverTip line). But I suspect that ultimately most similar products would work for your needs.

Consider the state of the remaining gelcoat on your hull. If there are many cracks, blemishes, dull spots you might go for painting the Hull entirely with a PU paint or something like that. In that case, you could just do an epoxy repair w/o adding gelcoat. (But you'd want to fill cracks).

Also, if you do want to repair thin cracks, you would need to widen them into a V with some scraping tool before attempting to fill them.
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hull thickness

Postby Roger » Thu Nov 20, 2008 10:46 pm

The hull just below the gunwale is 3/8" thick. I put a through hull there for a bilge pump, so I know this exactly. I suspect it may be slightly thicker on the bottom but not likely more than 1/2".
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