Casting an epoxy plinth

[DoubleEnder]

I’m thinking about fitting two cheek blocks on the side of my wooden, round section boom, and need something to allow me to mount the flat base plate on the curved surface. I wonder if I could somehow cast a plinth in resin? One side would have a concave curve, the other side would be flat.
It’s a 25 foot boat. The boom section is about 120mm, so all comparatively small stuff.
Any thoughts on the best way to go about this?
Thank you

 

[ylop]

You can but you essentially need to make a mould with the radius of the boom, together with the cost of materials (which you probably end up with a lot of surplus) might mean other options are easier? Eg it’s presumably a packer that end up in compression rather than carrying a big load? Find someone with a 3d printer (some libraries have them) and use a filament suitable for the outdoors - make sure the final part is printed solid (100% infill) if it’s in compression. Or you could make it out of wood - big hole saw or lathe to do the radius.

 

[DJA]

When I've made cleats for my round boom I wrap a course graded sand paper round the boom and sand the profile into the bottom of the cleat. You could do this on a thicker piece of wood to make sanding easier then cut to size for the plinth

 

[Poignard]

Bonding Fasteners and Hardware - Wessex Resins & Adhesives

See 'Casting a base'

 

[Fr J Hackett]

Or alternatively make it out of wood, either using a power tool or hand held rasp to achieve the concave surface by trial and error or even make a cardboard template.

 

[rogerthebodger]

You can get cheek blocks with either a flat base or a curved base to mount on round spars

 

[Tranona]

If you are using these Cheek Blocks you can bend the corners where the screw holes are to take account of the shape of the boom.

 

[oldbloke]

Mount the cheek blocks and then backfill with the epoxy

 

[justanothersailboat]

+1 for grab some wood and get carving.

 

[alahol2]

As it's a wooden boom it may be easier to create a flat on the boom rather than trying to fabricate a packer.

 

[William_H]

All good suggestions however if yo are determined on making GRP packing block you might find or make a male mold of appropriate curve. Cover with cling film for release. I would suggest use polyester resin (cheaper) and use lots of chop strand mat. So lay up a piece of mat on the curved mold. saturate it. Cut pieces of CSM to sit on the sides of the curve in progressive size. Then another piece right over the top. Eventual;ly you can get to something approaching flat top. When it is hard you can grind the sides to the right sized square and shape. You can lay up layers when the lower layers get to gel ie not hard but siff enough to stay in place.
Actually I dislike the idea of sheaves on the side of the boom. Just right for penetrating a skull. My sheaves are set in to top of tubular boom so sides are smooth.
You may be able to make a sheave box(s) to sit on top of boom. Or do as I did and find a broken carbon fibre mast to use as a tubular boom. Much lighter and so gentler on skulls. ol'will

 

[DoubleEnder]

Thanks to all for some good ideas. I will ponder. But this is very useful