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Stringer repair

Anything related to the operation of your boat. Steering, Bilge Pumps, thru-hulls, bottom paint, etc.
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Re: Stringer repair

Postby km1125 » March 27th, 2021, 6:26 pm

In areas where the stringer is not failing but you're trying to provide some additional support, I've always wondered if you couldn't marry a marine aluminum "Z" beam on the stringer and attach the engine mounts to that.

Something like this simple drawing. If necessary, you could extend them to the bulheads on either end and put a right angle connection to the bulkhead. I've seen several boats that actually have an aluminum channel frame that's attached to the stringers that is used as the engine bedding, so it's similar to that concept.

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Re: Stringer repair

Postby Viper » March 27th, 2021, 7:17 pm

bud37 wrote:Source of the post There is another angle to consider.......will you keep this boat for a while after the repair....if so what value would you put on it. It is possible you could put all sorts into this and get the same amount out. You could just use the boat up as it is then move it along when you want to move on or up.. :-D

I mean even if you find you need to repair this now, in another 5 years what is the value especially if you use up the engines in that time.....just another point of view to consider.....

I guess you will see what the surveyor has to say and that is a good move on your part....that moisture % you mentioned doesn't seem all that bad for now, but again that can be very tricky to measure accurately in the bilge.

Fibreglass Boats are funny things IMO, they are designed to flex so any repairs need to be done correctly or other issues will crop up.....good luck man and let us know what you decide.
I agree bud, you have to weigh all the circumstances for sure. One could also approach the situation like this; if the stringers are currently wet but sound, you'll likely get many years out of them before they get to a point where their integrity becomes problematic. If you have plans to move into a different boat eventually, leave her as is and enjoy. When the time comes to sell and the issue is brought up as a deficiency during negotiations, then negotiate a drop in price to compensate for the deficiency. What most purchasers will then do if they like the boat, is call around and try to get a ballpark cost for the repair and suggest that the drop in price should reflect that additional expense. I can tell you from experience that within reason, you should take it and run as the ballpark figure is always much much lower than the real cost after all is said and done. And if you decide to hang on to her because because you don't want to drop the price that far, you might be the one facing that huge bill for a complete stringer job, and I can tell you it will be way more costly then the negotiated drop in price a previous purchaser was asking for.

Of course there are folks that don't bother getting surveys so this might not be an issue at all. I don't like passing on a problem to someone else but it really is up to the buyer to educate themselves about a purchase that is likely to be the second or third most expensive thing they buy in life next to a house, that's why we always stress getting a survey.

Keep what ever documentation you're given regarding the stringers' current condition, it might come in handy later if the prognosis isn't that bad. If the stringers are still in good shape, it may be wise to also get a professional opinion in writing of the cost to remedy the deficiencies in their current state as right now it would only be a partial remediation. This might help negotiations in your favour later.
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Re: Stringer repair

Postby Cooler » March 29th, 2021, 11:25 am

Viper - please do not ever hesitate to disagree with me or anybody on this forum. The real value to this forum is the multiple perspectives we all get from any of our challenges. That, plus, everybody knows you are the most experienced, qualified source for feedback on our issues. I, for one, am very thankful and appreciative of your input in this forum. The frequency of your participation is also impressive. You provide a level of comfort/confidence to all us Carver owners. We are blessed to have a lot of sources to draw from. I don't disagree with your logic earlier in the string. That's why I am so careful to inspect for stress cracks every single time I am in the bilge. I still think we should set up a CYO rendezvous in the future. I will start the plan rolling, but going to wait till you can attend. You will be the celebrity draw to the event. Maybe 2022? 8-) er
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Re: Stringer repair

Postby Viper » March 29th, 2021, 7:01 pm

Thanks for the kind words Cooler. Don't know if I'm the most experienced but I have been doing this for a while and have had the privilege of working for dealerships, on many brands old and new, as well as learning/working in several industry disciplines. You get to know a thing or two doing that. It's not just a job and a hobby, I live this stuff. Wish I knew everything but I'll be the first to admit I don't. I've learned so much from you all here though, and you're more fun than a classroom! Let's keep it up, we're on a roll :down:
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Re: Stringer repair

Postby RGrew176 » March 30th, 2021, 9:54 am

Cooler wrote:Source of the post Viper - please do not ever hesitate to disagree with me or anybody on this forum. The real value to this forum is the multiple perspectives we all get from any of our challenges. That, plus, everybody knows you are the most experienced, qualified source for feedback on our issues. I, for one, am very thankful and appreciative of your input in this forum. The frequency of your participation is also impressive. You provide a level of comfort/confidence to all us Carver owners. We are blessed to have a lot of sources to draw from. I don't disagree with your logic earlier in the string. That's why I am so careful to inspect for stress cracks every single time I am in the bilge. I still think we should set up a CYO rendezvous in the future. I will start the plan rolling, but going to wait till you can attend. You will be the celebrity draw to the event. Maybe 2022? 8-) er



I agree totally with the above sentiment.
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Re: Stringer repair

Postby Superg » March 30th, 2021, 5:49 pm

I spoke with a Brian in Service at Carver for quite some time today. Very nice and helpful guy. Here is what he said.

In agreement with Viper, Carver wouldn't have used expensive marine plywood if it weren't structural. He believes there are 2 pieces of 3/4 Inch ply glued together in the stringers.

Regarding fix, he suggested sistering plywood on the outside of the existing stringers if necessary. If not he suggested just doubling the fiberglass over the affected area and making sure to stagger the tabs from each layer where they meet the hull by 2 to 3 inches. In other words, the bottom layer would have a 2 inch tab on the hull. The layer above that would have a 4 Inch tab, and the top layer 6 inches. That way each layer is bonded to the hull and not just the bottom layer. He said the top hat design has a 3/8 in think fiberglass wall and the active wood cores on boats like mine have 3/16 so that's where he got the doubling of the thickness. He said the top hat design may be wider, but that is for ease of forming, and it is the height of the stringer and the thickness of the glass that matter.

If sistering would be required, he also recommended coating with fiberglass and binding to the hull, but perhaps with only 1 layer since the sister would provide the structure in that case.

His preference was for the fiberglass-only method. In both cases of course he recommends removing any rotted wood and drying out the rest.

So there is our definitive answer from Carver regarding wood cored stringers!
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Re: Stringer repair

Postby Superg » March 30th, 2021, 6:07 pm

Regarding next steps for me personally with this boat. I plan on keeping it. She's a great boat and beautiful. I even put maple trimmed brazilian cherry floors in her. Engines purr, props are perfectly tuned. Hard to find a comparable boat without spending a lot more next time. That said, as with the floors, I always try to leave something better than how I got it. Just a personal need to fulfill. This year I will remove the small rotted portion around the limber holes and fill with epoxy. at the end of season I will dry out the rest and then add glass layers over the affected area and make new, properly sealed limber holes.

Thanks again for everyone's thoughts and help. It is what makes this forum great.

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Re: Stringer repair

Postby Viper » March 30th, 2021, 10:15 pm

Sistering a stringer is a fast remedy but it doesn't solve the underlying issue as I mentioned before. It's not the way I would go.

One of the best ways to create a limber hole in the stringer is to cut out a hole at the bottom of the stringer about an inch or two in diameter wider than you want the limber hole to be. Cut out a half moon shape at the bottom of the stringer with the flat side of the half moon being the hull. Get a plastic piece of pipe of the outside diameter that you want the hole to be and cut it down the center length wise, then cut it to length to the thickness of the finished stringer. This will be your limber hole or the mold for the hole. Have all of these cut and ready to go. Wet out the wood with slightly thinned resin so it penetrates the wood better. Let it tip off for a while to give it time to penetrate. While it's still tacky, place a section of pipe in the hole against the hull so you're creating a bridge. Fill the gap completely around the pipe/bridge (see note below) with thickened epoxy or polyester, whatever you're using, and let it cure completely. This way, there will be a good layer of epoxy/polyester between the hole and the wood core with no chance of water ever getting in through there. If it's done right, you may be able to remove the plastic mold but don't sweat it if you can't.

Exercise caution when filling that large a volume at once with resin. It generates heat to cure and when you fill a large void with a lot of resin at once, it could generate enough heat to start smoking or worse. At the very least, it will ruin your repair. You can use a slow cure hardener or fill the gap in layers, waiting for each layer to almost cure before adding more. This prevents the mix from generating too much heat.

If you're going to use epoxy, you need to keep in mind that during the curing process, it creates an amine blush on the surface that you must remove properly before you apply any coating over it like get coat or paint. If you don't remove the blush, the coating will not bond properly and will fail. You can remove the amine blush with warm soapy water, dry it off, and sand the surface before applying a coating. Some epoxies claim to be amine blush free once cured but I err on the side of caution and wash them down anyway. Also consider that gel coat bonds better to polyester resin than it does to some epoxies, that's why I mentioned using polyester instead of epoxy to do this job if you plan on using gel coat after.

It should be noted that the areas to be glassed over existing old fiberglass like the hull, should be ground down first for proper adhesion, no amount of chemical cleaning will give you the same results. This roughens up the surface and gets rid of any contamination for the best chance at a proper bond.
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Re: Stringer repair

Postby Superg » April 12th, 2021, 4:30 pm

Marine surveyor coming by tomorrow, and I'm giving him permission to take some core samples. From my observations and an initial core sample above one of the limber holes, it appears the entire stringer (and we can assume both inboard stringers) have too much moisture. Damp to the touch. That said, they are still firm away from the limber hole, and my core sample was solid once it air-dried, and the laminate is still firmly attached to the plywood. So I'm guessing this is what I will do:

1. Dry out the stringers. Must do this if you're not going to fiberglass over the entire stringer and make the core redundant. This will entail drilling a couple hundred holes or so straight through the stringers. Then creating a sealed "manifold" of sorts across the inboard stringers using plastic and duct tape. Then buying a commercial dehumidifier (about $700) and having it blow warm dry air into the manifold and drain the moisture through a hose and out the boat. Similar to what Dryboat does. I will do this with the boat in the water to keep the hull evenly supported. Don't want to try this on stilts. Can always resell the dehumidifier when done for $500 so only out $200.

2. Take new core samples and replace any section that isn't solid. Inject epoxy into the stringers a little at a time through the holes. Then epoxy and dowel the holes. Epoxy outside of doweled holes. Paint.

3. Seal perimeter of limber holes and build up bottom of limber holes with polyester putty so that there isn't a "cup" for water to sit in.
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Re: Stringer repair

Postby km1125 » April 12th, 2021, 5:06 pm

Elaborate on this part: "and build up bottom of limber holes with polyester putty so that there isn't a "cup" for water to sit in."

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