Making a pad to go under the davit fitting. Help please

[whiteoaks7]

Winter project number 3 - fit davits. Ok, the only problem seems to be that the transom is not horizontal so I need to build up the area onto which the davit socket will sit. I could use wood but (a) it will rot in the end and (b) the shape is awful - sloping from 8mm and 10mm to nothing in north-south and east-west directions.

So I think GRP would be best but I know nothing of GRP, so here are my questions:

1/ Can I simply use something like chopped glass filler from halfords? This seems to have the advantage that it will be easy to knead into the right circular, complex wedge shape. I would hope to be able to smear the stuff over the base of the fitting then wiggle it into the right orientation. Is this naive?
2/ Or do I need to build up the area with successive layers of mat and resin. If so, what mat do I want and are all resins equal? (I assume ester resin, not epoxy?)
3/ Whichever way I go I want to finish the rim with gel coat filler, of which I have plenty but it is too runny. Is there something I can add to the filler to bulk it (talc and marble flour ring vague bells) and where can I get some?

 

[tangofour]

If you can jig the davits in place you could possibly achieve a good result by using a paste of resin and cotton flock. Best approach would be to cover the hull with release agent and a sheet of dacron or similar release material. Do similar with the foot of the davit. Prop the davit in place. Push paste into the gap to fill it. Perhaps remove the davit and fill the voids in your filling attempts.

Trim and drill.

I'd be biased towards epoxy resin for the paste. 10mm is a thick moulding and the exothermic reaction could weaken the final article.

 

[ponapay]

Why not use teak, if kept well oiled it won't rot.

It is easy to cut to shape, removable and looks good.

I have replaced all my davit pads with new teak and also my windlass pad which has a complex shape and curvature. Windlass pad took about two hours, davity pads 45 min each.

 

[Spuddy]

Teak pads are ok under lots of things - winches etc.
Or - fairly easy to make up a mould out of smooth ply or similar. Tapering depth ( like a swimming pool) and sloping sides so moulding is easy to get out. Needs sealing then mould release wax. Fill up with resin + fibres - oh yes, gel coat first. Hmmm, maybe the teak would be easier

 

[Poignard]

This sort of thing is well covered in the WEST Epoxy literature [see Hardware Bonding]. It tells you how to cast neat sloping bases in-situ using thickened epoxy resin.

http://www.wessex-resins.com

 

[Swagman]

We took a recommendation to extend the load beyond just the transom and I'm glad we did having since seen several yachts with unsightly crazing to the gelcoat around their davit base.
Appreciate the davits get rated for dinghy and engine weight, but any bounce when underway will significantly increase the load and can lead to enough movement to craze surrounding gelcoat.
In our case, we extended down from the david base pad to a second 'flat' surface below deck to prevent any movement at all.
If I havn't made this clear or you want pictures of what we did - please just PM.
JOHN

 

[nedmin]

Have you got an electrical supplier that sells "Tufnol"? It is an electical insulating material than is very strong.You should be able to saw to a wedge shape with a hacksaw .Bakelite would also be OK. but tufnol looks more like wood.It will not rot.

 

[William_H]

If you have plenty of gel coat filler that will be ok for the molding of the base. A bit of a waste but then it doesn't keep for ever anyway. Use talc as a filler to make it less runny. Steal SHMBO talk or baby talc it is all ok. Just add enough while mixing to give the consistency you want. You might try a plastercine (moulding clay) dam around the base to form the resin into a suitable shape. Be carefull to not add too much hardener as already mentioned it can get to hot when hardening but should be ok with conservative amounts of hardener.
You could make a dam in a circle then fit the davit and foot on top and suitably support it and clean up the overflow. When the resin is hard drill through the spacer to fit bolts right through. You don't necesarily have to have release agent between the deck and the spacer and the spacer and the pole foot. Only if you want to get them apart again. Use plastic from shop carrier bags or cling wrap as a release membrane.
if you havn't used resin much try a dummy run to get the feel for it. (use disposable plastic gloves.)
I reckon that the spacer at about 10 mm on one side zero on the other will have enough compressive strength without needing f/g filler but you could put a bit in if you had it and wanted to.

As also suggested you need more support under the deck than just a large foot weded on the bottom of the tube. good lcuk olewill