Keel crack

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D&D
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Keel crack

Postby D&D » Tue May 10, 2016 7:01 am

Hi - i have PDQ 36 Vindand Hull #33. prepping the bottom for lunch and I have found a long crack where the keel meets the hull. photo attached - hope it works.

I am thinking I need to sand it and fare it out and fibreglass it. People on this board have talked about the keels being breakaway and mention of a foam portion of the keel that allows this. So I guess before I strengthen that area, I am wondering if I should do anything and if so what.

Anyone else run across this? I believe I read an old post on here saying another owner had the same situation and did a fibreglass repair, but thought I'd see if any else wanted to weigh in.

Thanks,

Doug
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keel crack.jpg

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thinwater
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Re: Keel crack

Postby thinwater » Thu May 12, 2016 8:36 pm

No one has responded, so I'll share what I know and what I surmise. I have a PDQ 32.

First, why did it crack? Either poor blocking (too much weight on the keel), ice, or a construction flaw.

Since the crack is straight I surmise there is structure there. Either the boat has a shallow sump or that is the bottom edge of a fillet. However, either way, there is only one repair:
1. Drill holes in the bottom of the keel to drain water. Small, and plug them after they stop dripping.
2. Grind a 12:1 bevel and fill with epoxy and 17 oz. biax (probably what it was built with. Roll the layers to maximize glass content.
3. Grind and fair.
4. Finished with a coat of epoxy.
5. Remove blush (wash)
6. Sand and paint.

Perhaps 3 visits + bottom painting, perhaps 3 hours of total labor if you are a fast worker, probably less. Easy.

I think the "sacrificial" argument is basically nonsense up there. It is not like the keels will pop off. What will happen if you strike a rock at speed is that the forward edge with crush without ripping the keel off the boat, since they are of much thinner laminate than the hull bottoms, only about 4 layers instead of 8.
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Page 83
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Re: Keel crack

Postby Page 83 » Sat Jun 04, 2016 11:17 am

PDQ 36 hulls were laid up in halves then joined down the middle. There is a 3-4" bump out at the lowest point to which is glued a hollow sacrificial keel. If you hit something hard enough to damage the keel it will crush or dent and fill with water, but since the hull is not breached, you can continue sailing safely, if slower. If you hit something less forcefully, the keel "sock" will flex, cracking the more rigid fairing material right between the lever and the hard place. I think this has happened to you, either in the water or while being moved on land, some time in the past. If the boat was dropped you might see damage to the plywood bulkheads supporting the floorboards above. The crack may just have happened after sitting on the keels for a long time.

In a few years, water will migrate into the appendage. After hauling the boat out and blocking it up so you can get to it, find something round and fiberglass like a broken fishing rod, and drill an equivalent sized hole into the bottom to let water out. Be surprised if there's less than a couple gallons. Don't forget to cut and glue a plug before you launch!

When you patch a crack in fiberglass, you create a harder place to crack. If the forces aren't reduced, you will get a crack somewhere else. Parts of the insde molding are stressed, as in around the stainless steel pipes that carry the loads of the shrouds down from the cabin roof. If you don't take those loads into consideration, you'll end up just moving cracks around.

The area where the keel is glued on is not continuously stressed. A somewhat flexible repair is desirable, just to seal the potential leak. You still want it to be "frangible". {crossword clue} It will have quite a bit of "Bondo" slathered around it, so if you are going to follow Thinwater's great instructions you will have to grind down to reveal glass cloth on both sides of the repair which will be a two level overlap rather than a butt joint. An alternative is to scratch out a Vee-shaped ditch where the crack was, and fill it with something just a bit more flexible. I would ask Thinwater for a suggestion.
Sandy Daugherty "Page 83" PDQ 36026

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Page 83
admiral
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Posts: 455
Joined: Sat May 08, 2004 11:48 pm
Location: Annapolis, Md. 36026

Re: Keel crack

Postby Page 83 » Sat Jun 04, 2016 11:17 am

PDQ 36 hulls were laid up in halves then joined down the middle. There is a 3-4" bump out at the lowest point to which is glued a hollow sacrificial keel. If you hit something hard enough to damage the keel it will crush or dent and fill with water, but since the hull is not breached, you can continue sailing safely, if slower. If you hit something less forcefully, the keel "sock" will flex, cracking the more rigid fairing material right between the lever and the hard place. I think this has happened to you, either in the water or while being moved on land, some time in the past. If the boat was dropped you might see damage to the plywood bulkheads supporting the floorboards above. The crack may just have happened after sitting on the keels for a long time.

In a few years, water will migrate into the appendage. After hauling the boat out and blocking it up so you can get to it, find something round and fiberglass like a broken fishing rod, and drill an equivalent sized hole into the bottom to let water out. Be surprised if there's less than a couple gallons. Don't forget to cut and glue a plug before you launch!

When you patch a crack in fiberglass, you create a harder place to crack. If the forces aren't reduced, you will get a crack somewhere else. Parts of the insde molding are stressed, as in around the stainless steel pipes that carry the loads of the shrouds down from the cabin roof. If you don't take those loads into consideration, you'll end up just moving cracks around.

The area where the keel is glued on is not continuously stressed. A somewhat flexible repair is desirable, just to seal the potential leak. You still want it to be "frangible". {crossword clue} It will have quite a bit of "Bondo" slathered around it, so if you are going to follow Thinwater's great instructions you will have to grind down to reveal glass cloth on both sides of the repair which will be a two level overlap rather than a butt joint. An alternative is to scratch out a Vee-shaped ditch where the crack was, and fill it with something just a bit more flexible. I would ask Thinwater for a suggestion.
Sandy Daugherty "Page 83" PDQ 36026


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