Glass new stringers afloat or on the hard

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Focused1

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Want to glass 4 half height stringers into my scanmar 33.
Should I do this afloat or on the hard?
Would also like to understand why.
Hoping for an experienced input if possible. Thanks (y)
 

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Do you mean ribs reinforcing across the keel or stringers to reinforces flatter sections like the topsides. The photo suggests you want to fit ribs by using the formers shown. I would do the work in the water as the hull is being fully supported by the water, but out of the water it will be a slightly different shape depending on how it has been supported and chocked.
 
Concerto said:
Do you mean ribs reinforcing across the keel or stringers to reinforces flatter sections like the topsides. The photo suggests you want to fit ribs by using the formers shown. I would do the work in the water as the hull is being fully supported by the water, but out of the water it will be a slightly different shape depending on how it has been supported and chocked.
Click to expand...

On the contrary, the area around the keel will be the thickest part of the layup and the most rigid. It's unlikely that it would change in shape significantly in or out of the water.
 
pvb said:
On the contrary, the area around the keel will be the thickest part of the layup and the most rigid. It's unlikely that it would change in shape significantly in or out of the water.
Click to expand...
Funny you say that. When chatting with a surveyor some years ago he said in the water was always best for any additional strengthening of any GRP hull. I have also heard this from a very well respected yard manager. So, we disagree again.
 
What type of material are those two stringers / formers / floors (take your pick) made from?
They look rather like polystyrene?
If they are, they will just disintegrate / melt if you try to overlaminate them with polyester resin.
Maybe they are just templates from which to cut the actual floors?
If so, what material do you intend to make them out of?
If you can guarantee that your bilge will remain bone dry while afloat then you could do it afloat, otherwise it might be better to do it out of the water, and make sure that the boat is 'properly' chocked / supported.
 
Stringers are longitudinal stiffeners running from the stem to the transom or stern post. The transverse stiffeners in the keel stub could probably be best described as floors . If the keel bolts don't leak and the area is bone dry doing the glassing in afloat would help dissipate any heat build up .
 
Lets call them ribs.
The formers are Expanded polystyrene. I am using epoxy. I have layed up over polystyrene before and it was fine.
Wanted to get cracking on this whilst afloat but wasn't sure if I was missing something.
Thanks all for the input.
Very helpful (y)
 
In my opinion, it will not make any difference because even if you do the job out of the water, the whole hull would have to be supported in such a way so that the weight of the hull would be distributed throughout, almost as if it was in water.
 
I would round off the top edge corners of the formers to allow the glass to conform to the shape more easily.

PS Ribs are vertical members that go from the keelson to the gunwhales floors are what you are creating.
 
graham said:
I would round off the top edge corners of the formers to allow the glass to conform to the shape more easily.

PS Ribs are vertical members that go from the keelson to the gunwhales floors are what you are creating.
Click to expand...
And stringers are horizontal, fore and aft members.
I can't see why the OP is doing this, as the lay-up in this area, around the keel, is the thickest, strongest part of the boat, usually.
 
pvb said:
On the contrary, the area around the keel will be the thickest part of the layup and the most rigid. It's unlikely that it would change in shape significantly in or out of the water.
Click to expand...
Spirit (of Glenans) said:
And stringers are horizontal, fore and aft members.
I can't see why the OP is doing this, as the lay-up in this area, around the keel, is the thickest, strongest part of the boat, usually.
Click to expand...

Unless it's in need of reinforcement.
 
I know little on this topic but have heard speculation that osmosis issues may be due to fresh material being placed on a damp surface , where dew has formed overnight. This could equally be a risk whether the boat is in the water or ashore. Plenty of ventilation and possibly some heating , possible use of a dehumidifier should take care of that.

In very cold weather the boat is in the water if may be at a higher temperature than ashore . The temperatures forecast this weekend seem remarkably mild for the time of year.
 
I would not do it in the water in the winter because of problems with condensation (dew points & all that),ashore you can raise the temperature with applied heat before starting a maintain a reasonable temperature with gentle heat for a while when curing particularly as it is a structural addition.
Jim
 
Pure supposition:
With the weight of the boat on the keel it is not difficult to imagine the sides of the boat being pushed out; with the more uniform pressure on the water, it is not difficult to imagine the sides being pressed in. I would do it on the hard, better to put the new ribs in compression.

Different form of construction but the floors on the Contessa 32 class have to be removed and put back in, in order to replace the water tank, As far as I know this is always done on dry land.
 
The boat will have been built with the keel off sitting either in a cradle (or, rarely it's mould). To restore it to 'factory' you'd emulate that by supporting the hull and hull separately.

If the boat is flexible in that area, as mine was, it almost doesn't matter, the chance of any broken fibres mending themselves is fairly remote. If there's an area where a crack has caused the gelcoat on one side to ride up and catch on the other then I'd move the boat until it was back in place and quit while I'm ahead. Fwiw I treated the flexible area of my hull as the bit that kept water out, and transferred the keel loads to substantial floors (much wider than the OP shows) and doubled the thickness of the hull out to the waterline. This is (was) a 60's one design where the idea of floors seems to have been undervalued. The fix transformed the feel of the boat.
 
Concerto said:
Funny you say that. When chatting with a surveyor some years ago he said in the water was always best for any additional strengthening of any GRP hull. I have also heard this from a very well respected yard manager. So, we disagree again.
Click to expand...

I'd say it depends on where strengthening is needed. as I said, the keel area is thick and rigid, so is unlikely to change in shape in or out of the water, whereas thinner parts of the hull may indeed deform out of the water.
 
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