Rotten stringers, need advice

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m1nder

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Folks, I am attempting to restore an old Norman 17. My latest nightmare is to uncover all the original stringers which are rotten. Would you mind having a look at these videos I shot and tell me what you think?

http://www.youtube.com/user/Ballymullaney
Particularly this one - http://www.youtube.com/watch?v=6gJOx5mJ_Xc

(excuse the sniffles, dust dust and more dust)

I'd be very grateful for any advice, particularly as to the architecture of the centre stringer in relation to the keel and what to do there next.

Many thanks in advance
 
Hi-

Reminds me of my 19' centre cockpit Europa.

That boat had keel damage from repeated groundings and dragging onto unsuitable trailers and a resultant leak and soggy wood inside a grp structure.

Not knowing your hull, my only comment would be that the wooden stringer, often softwood, may only have been there to form the real strength, the grp tube that you may have inadvertently removed?

Nick
 
Is the stringer actually only there to support the interior woodwork (floors etc). Does it really provide any strength to the hull?

I would replace them with hardwood and bond it in with Sikaflex 292
Got to be better than what is there now.
 
Yes I'm planning to replace all with hardwood, I already have the wood here and some tubes of sikaflex.

But really my question is, what am I looking at there? is that the bare open top of the keel timber or am I looking at the floor?

Would you drill into it?
Would you advise a centre stringer that runs the entire length of the boat? (the old ones were separate and ended at the centre under the cabin bulkhead
 
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I would take all the rotton wood out and fill the holes with structual grade fibre glass stringy stuff . Just a wild guess but i think any wood used to build a small pleasure craft like a norman is just a form that was easier to leave in rather than remove .
Normans etc ( same as my boat ) where made so everyone could own a boat in the 50's and 60's so not realy the best construction compared to the Mary Rose .
 
How to do it!

The area over the top of the keel should be part of the hull and a fibreglass skin. Sand a part of it to confirm this. As already said the fibreglass you removed is the actual strength of the stringer not the wood. You have not done anything wrong by removing it as there is no other way to solve this. Don't replace the wood with more wood though. We use plastic water pipe 22mm or 28mm for making this type of former and glass over it to the same spec' as the original stringers (probably about six layers of medium weight mat). Cheap and easily available from plumbers merchants!

You can check the state of the keel from the outside of the boat. Drill a few test holes in it to see what is inside and whether it is full of water. If all seems OK just fill the holes again with GRP in the usual manner.

What ever problems you find there is nothing that can't be put right!

Brilliant film by the way. Best and clearest question I have ever seen here. Well done and good luck with the renovation
 
PCUK said:
The area over the top of the keel should be part of the hull and a fibreglass skin. Sand a part of it to confirm this. As already said the fibreglass you removed is the actual strength of the stringer not the wood. You have not done anything wrong by removing it as there is no other way to solve this. Don't replace the wood with more wood though. We use plastic water pipe 22mm or 28mm for making this type of former and glass over it to the same spec' as the original stringers (probably about six layers of medium weight mat). Cheap and easily available from plumbers merchants!

You can check the state of the keel from the outside of the boat. Drill a few test holes in it to see what is inside and whether it is full of water. If all seems OK just fill the holes again with GRP in the usual manner.

What ever problems you find there is nothing that can't be put right!

Brilliant film by the way. Best and clearest question I have ever seen here. Well done and good luck with the renovation
Click to expand...

PCUK, Many thanks for that,
I have already dropped the side keels, they were rotten and saturated. I will replace these with hardwood and glass them in. I am using EPOXY so using woven roving and now biaxial cloth.

If I drill into the centre keel and find it's soaked and starting to rot, what then? I can't imagine dropping the centre keel and replacing it, my skills are limited, this is my first ever boat and proving to be a bit of a nightmare.
 
Things have changed since this craft was built, they used to use the timber as a cheap former to lay glass over, over the years the standard poly resin fails and water gets into the timber and the bond between timber and poly resin fails, even without moisture.

The prime cause of your failure was not enough glass in the first place.

You only need to grind back to a clean base to remove any old glue and just prior to applying you new epoxy/glass wipe the area with some Acetone.

The use of timber as a former has been replaced by using materials that are not effected by moisture that are lighter.

A length of conduit cut in half or half round sections of foam are common, I would avoid using the hard wood, save it for another project.

Pre cut your biaxial so that it lays along the curve, this will make it easier to avoid prickles sticking up in the finished product, 4 layers of 300 gram should be plenty.

If your keel timber is rotten you could simply glass over the external to provide the required stiffness and not have to worry about the timber inside.

If you want to dry it out first, simply drill 10 mm holes in a 50 mm grid and let it dry out on the hard.

As this is below the waterline an epoxy resin would be best but not sentential.

Good luck. :)
 
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