soft spot in hull

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soft spot in hull

Postby bburke001 » Mon Aug 17, 2015 6:54 pm

I have an '84 Spindrift DS1 - recently purchased. structurally the boat is great except for one spot on the starboard side hull about mid-boat (not sure if its below the waterline or not). There is a pretty good gouch in the gelcoat which someone did a shotty job of repairing with some sort of cement, but the crack is still visible. The hull is a bit soft in this area (gives a little when you press on it). I'm ready for a first dip/float test, but I'm wondering if I need to get this repaired ASAP before dunking. Also, I've not done any fiberglass/gelcoat repair - how intensive if the repair - or is this a boatyard job??
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Re: soft spot in hull

Postby NoCashOnBoard » Thu Aug 20, 2015 7:45 am

Doesn't look like anyone has responded to your question. I'll take a stab at it. I'm no expert on this just know enough to sort it out. An 84 Spindrift, does that have the double hull like the DS2 and DS3? I'm thinking it does, which means you won't be able to see if any water is coming in while you are afloat. You'll have to keep an eye on the bilge inspection ports. One indicator is did your boat have any water in the bilge when you got it, mine did about 10 gallons worth! One of my leaks was the transom plug which had no sealant around the flange. Fixing that helped a lot, I still get some water into the bilge, I'm thinking I've got a crack around my centerboard case. I'm not getting as much as I used to, though.

I would carry a bilge pump like one of these at all times: http://www.amazon.com/SeaSense-Hand-Bilge-Pump-20-Inch/dp/B004XACS30/ref=sr_1_1?ie=UTF8&qid=1440070551&sr=8-1&keywords=boat+pump It's the only kind that will fit into the inspection ports and suck the water out. A must have for sure.

On to the repair. You'll have to take all that gunk off that was put on, it's not an appropriate repair. You'll need a good sander or side-angle grinder and remove all of that junk and then sand about 3-6 inches around the damage area down to the fiberglass past the gelcoat. Hopefully the hole is not too big, which it shouldn't - a picture would help. Then you have to get fiberglass resin/hardener and fiberglass mats. I get mine from my local Canadian Tire automotive section. Your local auto parts store should have this stuff. You have to build up the repair with larger and larger sheets of fiberglass coated with resin. Once you have the right thickness, you have to sand it smooth. It's a lot like woodwork, if you can do basic woodwork you can fiberglass. It's real easy stuff to work with.

That should give you an idea what is involved in fixing this. I have a spot like that too that I have not messed with. It's real ugly and I don't know whoever did it what they were thinking. Next spring I plan to flip the boat and see if I can fix the centerboard case and I'll do that spot at the same time. Watch a bunch of YouTube videos and ask a bunch of questions, then just go for it. Nothing like learning is doing. These boats are great to learn this stuff on. You can't go wrong doing it yourself.

One more thing I use regular old bondo from the auto store for my fairing compound (stuff to make the job look smooth). I know it's not marine grade but my boat isn't sitting in water all the time. It's okay for that, but if this is going to be in the water a lot you may want to get the marine stuff. It just cost a whole lot more. As you probably have learned anything labeled marine warrants a premium. Somethings yes you want marine grade other times it's overkill.

Keep going. You'll get there.
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Re: soft spot in hull

Postby willyhays » Thu Aug 20, 2015 11:33 am

To add to what NoCashOnBoard has said, there a few important things to consider before deciding how to deal with the damage:
1. To what extent has the damage compromised the structural integrity of the boat? At the risk of stating the obvious, the greater the loss of integrity, the more critical the quality of the repair becomes.
2. How large is the damaged area? (It's common for the fiberglass to be damaged beyond what is readily visible.)
3. As NoCashOnBoard has said, it is essential that all traces of the original repair be removed unless you can verify that the repair was properly executed. This is especially important if the old repair was done with epoxy resin.
4. Probably the two most important factors that determine the effectiveness of fiberglass repair are the quality of the bond between the original fiberglass and the repair fiberglass and the accuracy of the resin/catalyst mix. To ensure a good bond, proper surface preparation is essential. Without that, a repair may look perfect, but, in fact, be structurally unsound. As for the proper mixing ration, it is not difficult to achieve, just critically important. As long as the manufacturer's instructions are followed the result should be adequate.

As NoCashOnBoard has mentioned, there are many youtube videos available. A couple hours spent watching those will be a huge help.

Hope that helps.
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Re: soft spot in hull

Postby rnlivingston » Thu Aug 20, 2015 12:28 pm

The Spindrift DS1 hull is made of a sandwich of fiberglass on two sides with a balsa core. The advantage to this is a very stiff hull without adding weight. The disadvantage is if the hull is breached, water gets in between the glass layers and rots the balsa forming a soft spot. If the existing repair is on the outside, I would cut it out and see if you can remove the wet balsa. While you could replace it with new pieces of balsa, instead I would epoxy in some fiberglass matting and finish it off with fiberglass cloth. Correctly done, you shouldn't see the repair.
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Re: soft spot in hull

Postby GreenLake » Thu Aug 20, 2015 1:24 pm

No need to involve a boat yard.

If this is close to the end of the season for you, I would suggest you sail the boat first, then work on a repair while you can't get on the water anyway.

This is assuming that the damage is as localized as you implied, which is hard to double check from a distance. "Crack is still visible" can mean that on can tell there's been damage, to "there's a crack still open". In the latter case, you might want to do something temporary to keep water out, esp. in light of the claim that these hulls are cored. For a small crack, a layer of packing tape might be all that's needed to "stabilize" the patient.

Before you launch into an actual repair, first, read up about it. West System and System Three are epoxy resin vendors that have publications on their site about the basics of boat repair with fiberglass. Both are worth reading. There are also many repair oriented posts here that you could look up. Again, if you can put off the repair until the off-season you'll have more leisure to prepare.

I really wouldn't use Bondo, because it's not intended for applications where it can be immersed; if you like the convenience of having a fairing compound pre-mixed, get System Three's QuickFair (an epoxy based product that is easy to use).

For the repair the first consideration is to make sure the damage doesn't spread, the second is to restore strength and the third is appearance. To the various suggestions about opening things up and grinding away anything remotely questionable I can't really add anything. If the hull is cored, it's paramount to get all the moisture out (by removing any wood that got wet). For a small-ish area, you may indeed simply use laminate (cloth and epoxy) to build up the hull, or you could use a filler (3m high strength marine Filler). When you add epoxy and glass to restore the outer skin, you may benefit from using a flexible yet stiff piece of plastic over the repair (to align it with the existing hull curve).

The question is how you will finish the repair? Gel coat? Paint? The epoxy needs to be covered so it doesn't degrade from UV. It's possible to patch gel coat (read up on it), but you need an covering sheet (or the gelcoat will not cure, doesn't cure in air). Same sheet helps get a fair surface. Or you could paint the spot, or, paint it and then plant some decal on it (depending on where it's located and whether you're more into looks or function).

As you can see, there are many ways to skin this particular cat, and you'll have to make some decisions as to how you want to approach this, and what your goals are.
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Re: soft spot in hull

Postby bburke001 » Fri Aug 21, 2015 8:18 pm

Thanks guys for all the input - here's a couple of shots of the spot
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IMG_0445.jpg (201.06 KiB) Viewed 11808 times
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Re: soft spot in hull

Postby GreenLake » Sat Aug 22, 2015 12:31 am

So about 1/2" to 3/4" wide scrape with about 4" to 8" in length? Hard to tell without anything giving scale.

I'd suspect the laminate for at least 2" all around.
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Re: soft spot in hull

Postby NoCashOnBoard » Sat Aug 22, 2015 10:25 am

It's ugly but repairable. Clean out the coring like GreenLake says. This is below the waterline, you'll need the good filler from the marine store or you can order from http://www.jamestowndistributors.com/userportal/main.do?engine=msn&keyword=jamestown_distributors_marine Jamestown Distributors. They have good prices.

Get the matting to cover the top layer, it's good for sanding smooth (the straw looking stuff) for the repair. Then just paint with topside paint and you should be good to go. I would take care of this before you do try the boat out, though.
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Re: soft spot in hull

Postby GreenLake » Sat Aug 22, 2015 2:28 pm

Fiberglass mat, also called chopped strand mat, has binders that dissolve in styrene found in polyester resin, but not in epoxy. West System report (http://www.westsystem.com/ss/chopped-strand-mat-epoxy/) that mat can be used with epoxy, with some limitations (with the binders not dissolved, the mat remains stiffer and thus more difficult to use on more tightly curved surface. Also, the binder will get enclosed in the epoxy, which means that the mat will not become clear (as fabric would be).

So you may hear advice against using it with epoxy. However, I've used it in various projects with success. It does provide bulk and it can be worked in ways that are a bit different from cloth, so some people recommend it as the inner layer over an uneven surface.

If you are not familiar with epoxy and fiberglass work, take a sheet of plastic on flat workbench and laminate an 8x11" sandwich of 3-4 layers of both cloth and mat. That will give you a feel for how the material works, and if you made any mistakes and the epoxy cures too fast or not at all, you can discard the attempt. If you are successful on the first try, keep the result and you will find some use for it later. (For example, I had a hull puncture in my single hull where using a backing plate of about that dimension was the thing to do, but you could also cut strips off of it - there are many uses for this).

I agree with the cashless guy that this looks too big and too low to be left unrepaired. However, once you've got it watertight you could use it, while epoxy doesn't like UV, it can handle a few days in the open if you rather try out the boat before fairing, sanding and painting.

For sanding, first I would try to minimize the need for it, by using a stiff plastic backing sheet to make the repair conform to the hull curve. Second, I would use QuickFair or similar epoxy based fairing compound to fill any low spots. FInally, for painting, Pettit EasyPoxy is a single component paint that I found easy to work. It takes a while to get fully hard, but it's pretty tough (despite the name, there's no epoxy in it).

That said, you could attempt to patch the gelcoat, instead of having a small spot that's painted. People sell gelcoat repair kits. I do like the ones that are pre-tinted for various shades of motorboat hulls. If you can guess which one matches the DS, then you just mix in the required number of drops of catalyst, spread it over the repair and use a plastic backing sheet to both make it conform to the hull and to exclude oxygen (else the gelcoat will remain sticky). You would need to leave your fiberglass repair a bit hollow so the gelcoat can be built to a resonable thickness, and you'd need to be sure the epoxy is correctly mixed and any amine blush removed with soapy water (scuff sanding the surface also helps). Gelcoat will bond to epoxy (despite what you read) but not if the epoxy is not mixed well or not in the correct proportion or has amine blush.
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Re: soft spot in hull

Postby willyhays » Sun Aug 23, 2015 10:59 am

Lots of good info here! Here is one of the publications that GreenLake mentioned. I found it to be very helpful. Also, Gougeon Brothers (WEST System epoxy) has a technical advice hotline staffed by super friendly, knowledgeable and helpful folks.
http://www.westsystem.com/ss/assets/How ... enance.pdf
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Re: soft spot in hull

Postby BettaDuck » Mon Aug 24, 2015 9:15 pm

I have a 68 DS1 and have a Y shaped crack and soft spot on my port side- looks like impact damage either from the bow of another boat or the pointy end of a dock. I ground out the crack on the outside of the hull as described in an earlier post. I also ground down the area inside the hull. When I did that I could see that my hull has a balsa ( I assume) core which had rotted away in the area of the crack so that if I put my hand over the side I could look from the inside and give myself the finger- like a slightly opaque porthole. Anyway ,the soft spot means the core is compromised- push on other places and you'll probably find the hull is firm, like I did. I made a repair with fiberglass to keep the water out so I can do some sailing but will eventually have to do a better repair. I just can't afford the expensive epoxy resin and materials right now, and need to do more research as I have never attempted that kind of repair and am nervous about cutting a hole in my hull.
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Re: soft spot in hull

Postby GreenLake » Tue Aug 25, 2015 5:53 pm

While a repair with epoxy had the advantage that the epoxy bonds so much better to cured polyester, there are some people who swear by using polyester (or vinylester, which is similar but "better"). I'm not sure I agree with them, but the point is, your repair could be more permanent than you were planning on.

When my boat got T-boned by a small but apparently very unyielding dinghy, I added a bit of additional reinforcement on the inside of the hull. I used a flat sheet of laminate that I made up on a bench and then glued (with epoxy) onto the inside of the hull. This did three things for me:
  • it helped the single laminate (no coring) of the hull to come into an alignment again (the crack's edges where not aligned after I ground away much obviously damaged laminate around the impact).
  • it added strength over an area larger than the visible damage, meaning I didn't have to remove as much of the existing laminate on suspicion
  • it was easier and less messy to work, especially at the location the damage was in.
If it wasn't for the first point, the one about alignment, I could have laid up the laminate on a sheet of plastic and transferred it, as one piece, to the damaged area while still wet. As a process that is less messy than doing the layup on a vertical surface, and the plastic backing makes for a smooth surface after it cures.

If the affected area is small, you could replace the core with a suitable filler as mentioned in earlier posts.
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