UK-Cherub Class

Get Your Heart Racing


Spreaders

Design

Classically spreaders served to push the shrouds away from the mast, thereby improving the sideways force on the hounds. This means they were in compression, and some even had a hinge at the mast end!

Now they are used to push/pull the middle of the mast, which mean very great bending loads are put on spreader. This means they need to be strong, and attached across the whole diameter of the mast.

Spreaders also take a beating when rigging or when carelessly stood upon in the boat park.

All of the above means you need to put quite a few fibres running in all directions when making spreaders. We did this with guidance from Dave Roe.

The length of the spreader and the angle of the spreader are not covered in this article, but I will say that if you have shrouds which go to the mast by the spreader roots (called D2's or D1's), then you need the spreaders to be angled back such that they are pushing the middle of the mast forwards against the D2's holding them back. If you don't have D2's then you want them neutral or forward so they keep the middle of the mast back.

Build

Foam

Decide on the length (you can always trim / extend them later), and draw out an isoceles triangle which is the length of the spreader long, and the base is the diameter of the mast. Make the pointy end not a point, but cut it off to make an edge about 15mm long.

Cut this shape out with four thicknesses of 8mm 80kg foam. Glue them together in pairs using some epoxy and some filler (doesn't matter which) to make two 16mm thick rather boxy foam spreaders.

Go to the movies while it is all going off in the oven on a low heat (55 degs C is about right)

Shape the foam with 80 grade sandpaper. Keep the bottom flat and just sand the top until you have something that looks like a spreader. Try to make a smooth taper to about 6mm thick at the pointy end.

Gouge out the flat side at the thim end so a part of a stainless chainplate can fit in flush and bog it in there, and smear the entire surface with a trace of the epoxy filler mix.

Carbon

Put the spreader down on a bit of newspaper and draw round it. Roll it over like a rolling pin and draw round that, and do it again until you have gone round 3-4 complete revolutions. You'll end up with a shape on the newspaper like half a flower, as the spreader will turn as you roll it. Do it again with the other spreader.

That is the shape of the carbon cloth you will need. Any kind of 200g weave will do. We used plain weave, but 2:2 twill would be fine.

Cut out enough peel ply to completely cover each spreader once, plus a bit of overlap.

Cut out two bits of carbon to match the shapes marksed on the newspaper.

Wet out the cloth on a big sheet of plastic.

Apply the spreaders and gently roll them up in the carbon. The conic shape of the spreader ensures that the fibres will run in every direction, giving the properties you want.

Add the peelply and use the convex shape of the spreaders to really yank on it hard to help consolidate the layup.

Stick it back in the oven and go away.

Finishing

When it has gone off, pull the peelply off and enjoy your handiwork.

Make the spreader a good fit to the mast by using a holesaw with the same diameter as the mast at the thick end of the spreader. Don't forget the spreaders will want to be angled up to bisect the angle through which the shroud is turned. The easy way to work this out is that the upward gradient of the spreader = 0.5 * the distance from the spreader to the hounds along the mast / the length of the spreader. “A bit” is usually the answer to that equation.

Bog the spreaders on. We used a hot glue gun to attach them instantly before a big fillet and 2-3 layers of carbon went on.

Tidy up. Go sailing.


tech/spreaders.txt · Last modified: 2013/06/25 15:55 (external edit)