Hulllayup thickness.

[Norman_E]

I know that in the early days of GRP boats there were some very thick hull layups, because it was a new material and nobody was completely certain how much was needed. I recently had to remove an old depth sunder fitting to put in a new one. The nut had been bonded to the fitting and the only way to get it out was with a holesaw from underneath. Once I had done that I measured the removed fitting from the nut to the end and subtracted the thickness of the flange that I had cut off. The result was 16mm which was thicker than I thought it would be, and a quick check of the hole before inserting the new fitting confirmed it. I was quite pleased that it was so thick, as I had thought it would be less than that. The boat is a 1998 Jeanneau 45.2. Is that hull thickness typical of the era, and are more recent boats thinner?

EDIT: Darn it, you can't edit a typo in the title!

 

[prv]

Have to say, 16mm on the bottom of a 45 foot boat doesn't sound particularly thick to me. I'd image a real old 70s battle-tank would be an inch or more, though I've never drilled a hole in one so don't know.

Pete

 

[Ammonite]

Sounds about right to me too. I've a Hugo Du Plessis book somewhere that outlines typical thicknesses for different areas of the hull

 

[pampas]

1973 Cheverton 26ft 4" down amidship core for skinfitting is 1/2" thick Gel coat about 3/16". Can anybobody beat that?

 

[Norman_E]

That must be the thickest ever gel coat, and if you mean that the total is half an inch the actual layup is pretty thin, but 1/2 an inch of layup plus 3/16 inch of gel coat would be good.

 

[saltylegs]

I replaced sounder unit on a 79 Sigma at the weekend and the hull on the center line was over 30mm

 

[Chalker]

Echo Sounder on 1984 Westerly Corsair, 30-35mm layup.

I put a 98 boat in the thin ones!

Wonder what a 2000 Bav has?

 

[TradewindSailor]

Are you sure this is a representative hull thickness? Production boats usually have specific area allocated for the insertion of through hulls, especially if the hull is cored.

 

[Tranona]

Exactly. Just measuring the thickness at one random point says nothing about quality or strength. Some boats get strength by just piling in the GRP with no attempt to work out whether it is necessary, others engineer a structure that has varying thickness and composition depending on strength required.

 

[jwilson]

Jeanneau are quite good at adding a bit of thickness to the layup where through-hulls are to be fitted and where more stress is expected: I very much doubt if a 1998 boat has 16mm all over the hull bottom.

 

[wooslehunter]

Bottom of my westerly centaur 1974 vintage is around 30mm!! Built like the proverbial bsh....

 

[Tranona]

Bottom of my westerly centaur 1974 vintage is around 30mm!! Built like the proverbial bsh....

Does not however mean that it is 30mm of good material. Seen a Centaur where the whole area between the keels disintegrated into mush when the blistered gel coat was blasted off. Had to take the internal sole out and mould in a new bottom.

 

[Norman_E]

Jeanneau are quite good at adding a bit of thickness to the layup where through-hulls are to be fitted and where more stress is expected: I very much doubt if a 1998 boat has 16mm all over the hull bottom.

I did realise that hull thickness would vary, and the boat has a grid of stringers that divide up the bilge so that it is hard to see if some areas are thicker than others. If there were deliberately thicker patches for through hulls they should be visible as raised areas inside, but none are apparent, even in the heads where there are multiple through hull fittings.

P.S. I did not invent a new word for the title of this thread, it is just a Chinese gentleman exhorting us to go faster.