UK-Cherub Class

Get Your Heart Racing


Exultant Jubilation - The Build

The chronology of the build will appear here when I get the photos.

The end of the build Sept 2009

A Little less conversation...

...A little more action

With the door to the Room of Requirement now officially sealed1), we have moved the boat and all of the rest of our junk to my parents garage in Sidcup.

Living in Holland is cramping progress a little, but at least the long lonely evenings without Hayley have been put to good use. A public thanks to Dave G. and Rob L. for not minding me turning our sitting room into a sail loft.

Many thanks to Allen (and Harbour Wall) for the fitting package. We hope to get everything wet as soon as we can…

[[http://www.allenbrothers.co.uk/]]

What went into the boat - Cookbook

The following is a description of the layups used in various parts of the boat.

Hull

Skin

The outer skin is made from a carbon sandwich. 200gpsm carbon weave vac'ed onto a male mold. 8mm thk 80gpsm (gram/m^2) foam stuck down to that and then 200g/m^2 carbon weave vac'ed onto the outside. The bottom panel has a second layer of 200gpsm from the stern to about a foot past the mast foot (resulting in a thicker laminate for some stone protection).

Butter. Both sides of the foam was buttered. Butter was used to stick the foam to the cured carbon, but on the outer surface it was allowed to dry and then the hull faired before the outer carbon was added. Butter reciepe used - 260ml of resin mixed to a tub of bubbles (tub previously contained M&S chocolate bites). Butter spread using a window squeegy.

Deck

As per the hull. Extra glass layer added where the crew are likely to stomp.

Bulkheads

Made with a simialr sandwich to the hull (200gpsm carbon weave, 80kg foam) laminate on each side was not parallel(but did not achieve 45 degrees). Additional unis run diagonally accross the main bulkhead and under the amst stump to ensure the load is distributed.

Mast Bottom Section

Mandrel

Made Mandrel on an (~52mm) OD plastic tube mandrel. Prepped with a good layer of silicon spray and then lamintated ontop of.

Hit 1

1 layer 200g weave, wound helically in 150mm (6“) strips to give +/- 45 fibres (10mm overlap between helix rounds). Consolidate well or “strangle”. 4 layers 300g uni - as 0 degrees as possible. Consolidate well or “strangle”. 1 layer 100mm wide peel ply applied in 50% overlapping helix in the same direction as base layer. Really beast this on. Some breather and vac down with a very thin bag - this results in few wrinkles and no “pinches”. Establish the vaccume using only the surface of the plastic pipe, so it does not encompass the ends as otherwise the bag gets sucked in and bursts. Lay pipe on the floor whilst curing and line up the floppy item with something straight (a couple of bits of 4×2 works a treat).

Bake - for this we used a tea urn, some plastic tubing and a central heating pump to circulate the water.

Hit 2

Be brave - leave it on the mandrel, but rotate the mandrel inside the mast first to ensure it has not got stuck. Sand off the helical leftovers form the peel ply and then add a layer of 0-90 weave. Peel ply, vac and bake as Hit 1.

Mast tip

Mandrel 1

2m tip, Mandrel tapers uniformly. 24mm OD at tip, 50mm OD at 2m from tip. This needs to be machined down once made to allow joint at 52mm ID of mast bottom section.

Madrel made by hammering some 10mm thread (with nuts on) into a 25mmOD scffold bar. This “tapered bit of metal” was then coated in wood, by routing a channel into some 2×4 and gluing the wood/metal/wood sandwich togehter. The resulting 4” square wooden object with a metal centre is then ready to shape.

The next bit is fun. Make a parrallel jig big enough to fit your object into (i.e. 4“ wide), check your power plane can sit ontop of both sides at the same time withouht cutting into the jig. Support the ends so the centre of the wooden sandwhich can rotated at the correct height off the sides of the jig at each end (i.e. centre of one end is the fat radius down, the other end is offset the thin radius down). Use a power plane to cut until you hit the the jig sides, rotate, plane, rotate, plane, rotate. This creates more shavings than you could ever believe, but results in a round uniform tapered object.

Nearer the tip you may need to strip out the outer wood to reveal the scaffold bar and then support the bar here. This extra bit can easily be filled and faired after the rest is shaped. Ensure the taper is selected so you do not need to plane through the scaffold bar!

Once shaped, sand until the thing looks like a snooker cue. To finish the mandrel heat a number of “tealight” or similar candles and use a small roller to apply wax to your sanded “wooden” mandrel. Keeping the wax hot ensures you can roll out any bubbles in the wax (we found this easier than ironing the wax).

Hit 1

1 layer +/-45 200g. Applied as a helix as before. Cut tapered uni cloth for the tip. Apply 4 layers of 300g uni, start at 12,3,6 and 9 o'clock around the madrel to ensure there is a good distribution of o fibres around the taper. Peel ply, vac and bake as lower mast

Hit 2

Weave. (200g at 0-90) After baking remove the vac bag,peel ply and anthing holding the carbon onto the mandrel. Tie around the carbon to hang it from the ceiling and then bake some more. Mandrel falls out of bottom :-)

Hit 3

Measure ID of mast bottom section. Run some tape around a suitably sized hole saw and then ram it down the fat part of the tapered top section. Rotate on a power drill and use a sanding paddle (or random orbital) to create a flat uniformed OD section to socket into the mast base. Wear a mask, gloves and full body protection for this step - there is a lot of carbon dust. Join mast tip and bottom section with the epoxy of choice (I used my standard epoxy with fibres, others swear by spar bond).

Mandrel 2

This is a revised tip section to give a stiffer mast for use with our sail-plan. Mandrel 1 was too floppy at the tip - worked well with a Fyfe cut sail though! If you are making a mast for a Mandrel 2 tip we would recommend adding an additional layer of 300gpsm UD between the two spreader sets. This results in a mast that appears compatible with the standard Hyde sails (Daemon, GT60 or Ronin cut) - please contact the author before bothering Hyde!

1.8m tip section. Made by adding a timber sandwich around a 25mm OD scaffold bar (these are thin bars used for handrails). Mandrel was machined by rotating under gravity - resulting in a 25mm OD mandrel at tip and 50mmOD mandrel at 1.8m from tip. Mandrel taper is not linear - more gherkin shaped. From 2.8m onwards mandrel did not taper, to make fitting possible without lots of sanding.

Spreaders

From mast tip

Item Mast 1 Mast 2
Tip2m1.9m
Goose neck5.7m5.7m
Length of top spreader (from mast face)40cm40cm
Sweep backwards (from mast face) 19cm19cm
Length of bottom spreader (from mast face)40cm45cm
Sweep backwards -bottom (from mast face) 19cm16cm

Middle spreaders at 1/2 way between Goose and First spreaders. The Mast 1 figures are before the addition of the “boots”, these were added and resulted in the Mast 2 dimensions

Spreaders made by shaping some random offcuts of foam. Would suggest they are bigger than you think necessary <attach picture> we broke a few on Born Slippy's mast so a went overboard on Exultant's. Layup is 6 layers of 200, some 300, some weave and some other offcuts.

When attaching spreaders we sat the tube on the floor and positioned cardboard boxes at the spreader position. After careful measurement and drawing on the boxes, the spreaders were then hot glue gunned onto the boxes. The individual spreaders were then bogged in place. Once set, a couple of layers of weave were then vac-ed over the join to make the joint even stronger.

<Insert picture of mast sitting flat on the tips of all 4 spreaders! >

Racks

Built on mast lower mandrel mast lower but with 3 layers of 200g uni (plus 2 layers of 200g weave, one helical at +/- 45 and the other at 0-90)

Mast stump

Built on mast lower mandrel but with 8 layers of 200g uni (got scarred and bored whilst laminating)plus helical and 0-90 weave. .

Rack supports front

Built on mast lower mandrel but with 6 layers of 200g uni, plus helical and 0-90 weave. .

Rack supports rear

Built smaller diameter plastic pipe 35mm OD plastic pipe. This was the size of the waste outflow from the bathroom sink (B&Q). 8 layers of 200g uni, plus helical and 0-90 weave. This mandrel is still inside the tiller, which is only 2x layers of weave.

Tension Struts

Laid up on a bit of wood with a wedge at one end (mandrels CO Andy P and also the kirks) the struts were made of 10 layers of 300g uni. If made again I'd do 5 layers uni, 5 layers glass weave, 5 layers uni. Thicher, but then you would be able to grab them when in the water without fear of breakage…

1) See Harry potter for an explanation of why a dis-used church hall in Bethnal Green that appeared from thin air, became our workshop and contained every tool needed to build a Cherub was thus named

tech/3206build.txt · Last modified: 2013/06/25 15:55 (external edit)