Repairing Foils

-Minor damage only.

Catapult Dagger board foils are designed to pivot aft when grounded. This will prevent damage, unless of course you hit something really solid. But they can be damaged in other ways, like incorrect storage or rough handling, etc. When you sail back into deep water after grounding, the affected foil will return to vertical and can be lifted up. If you sail into shallower water it won't lift up, but will eventually “break away” from the front channel. This means it won't be lost (it's held by a bungee cord), but it will probably sustain damage as shown in Fig 1 and as demonstrated in Figs 2a-2d. From the vertical position, Fig2a, the bottom is Fig 1. Ouch! pushed rearwards causing the thin trailing edge to slide and pivot on the bottom edge of the rear channel. Once the angle reaches about 45°, the leading edge will exit the bottom of the front channel, Fig2b. Bungee tension or the ground will then lift it up, Fig 2c. The trailing edge is still captive within the bottom of the rear channel, but the free leading edge will twist, Fig 2d. The square cut end of the channel then snaps a chunk out of the foils trailing edge, much like a pair of pliers would do. Photos show the modified rear channel that won't trap the foils trailing edge. Fig 1(above) shows three chips, each one having been snapped off at a different angles. Lowering dagger boards on the move can also cause this if you miss the front channel and it twists. Note: Lifting foils, other than for weed removal, is now “illegal” while racing.

Fig 2a

Fig 2b

Fig 2c

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Fig 2d

Modify the Rear Dagger-board Channels. Having spent a lot of time and energy repairing my own chipped foils (details next), I realised that the chip damage can be prevented by simply cutting off the sides of the rear dagger-board channel at 45°.

Tools; 45deg Set-Square, Pencil, Hacksaw. Cut as shown in Fig3. Note that nothing is cut off Fig 3. Modified Rear Channel (inverted) the total length.

Repairing chipped foils There's no immediate urgency for repairs, as I doubt if a few missing chunks will affect your sailing much. So wait for a suitable “warm” day or two to tackle it. Unless you have a heated garage. Previous experience of fibreglass and resin will help with this job. But for the purpose of this article I'll assume you have none.

Materials – •

One small glass fibre repair kit which contains resin, hardener, and some squares of glass matting. Or buy resin and glass matting separately for about delivery off eBay.

£15 including

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A cheap 1 inch paint brush (for the resin) and some thin vinyl gloves.

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A small tin of cellulose thinners or acetate. (for cleaning or paint thinning)

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Some lint free cloth or 'Tag Rags'. (sticky gauze material to pick up dust)

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Abrasive papers – one sheets each of 80 grit & 40 grit Aluminium OxideProduction Paper (for dry use) & one 400 grit 'wet or dry' paper. (for wet use)

•

An off cut of softwood, for a sanding block. 9about 20mm × 40mm × 200mm) (Return to Catapult Home Page) (Return to Repairs and Mods Page)

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A Small tin of Car Body Filler Paste.

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A spray can of white Plastic Primer.

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A spray can of white Cellulose Primer Surfacer.

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A spray can of Cellulose Enamel (colour to suit)

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One pair of old scissors (not from the kitchen!) to cut the glass matting.

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Two pieces of scrap flat boarding or shelving (approx 20cm x 20cmm) and a couple of pieces of flat rigid plastic. (old number plates for example)

The repair work is fairly straight forward for anyone with DIY experience.

Getting started No need to dismantle the foils to repair this sort of damage. If spraying later, you may need to mask off some parts. Start by tapering the edges of the damage with 40 grit production paper. Power tools are a bit fierce for this work. But if used go carefully, as the foil material is quite soft.

Fig; 3. Two layers of woven matting on each side of each chip should be fine for most minor damage.

Taper each chip back 30 or 40mm onto the undamaged area, Fig; 3. This will help with adhesion of the resin, and provides some depth for the reinforcing material, e.g. chopped strands or woven glass matting. Leave enough depth for 2 -3 layers of matting to sit just below the finished surface. Small chips, Fig; 4 below, will only need one or two layers of glass matting on each side. Cut some suitable sized 'half circle' of glass matting to cover the roughened and tapered areas. Optionally cut some smaller sized 'half circles', again, one for each side of each (Return to Catapult Home Page) (Return to Repairs and Mods Page)

chip.

Use a flat board – a piece of shelving, floorboard or plywood etc. Anything about 10mm thick will do as a solid base to work on.

Fig 4. Woven glass matting ready for use

Find some rigid plastic sheet, like a number plate, to use as a former. Something that the resin won't stick to and with a smooth flat surface. If unsure, lay a small piece of polythene sheet on top of any rigid smooth surface. You'll need a heavy weight as well (a brick will do).

Resin and hardener:- Use thin vinyl gloves to keep resin off your skin. Read the instructions on the tin carefully regarding safety, minimum air temperature, and the amount of hardener to add etc. Have everything to hand before mixing any hardener to the resin; In hot weather you may only have 3-5mins before the resin gels, and becomes unusable. And ruins your brush. If this is your first time with resin, go through a dummy run of the operations first to get the routine fixed in your mind and that everything is within easy reach. When you do it for real with catalysed resin, the matting may stick to your brush, and the resin will probably 'go off' fast. If it all goes wrong, check there's no naked flame near, then use acetate to clean your brush. Wipe off as much resin and glass mat as you can from your container and work-piece. Let everything harden. Have a Beer, chill out, then later you can rough up the surfaces and start again.

On to using the sticky stuff then... Set up a work table with your flat base support timber on it. Lay your piece of flat rigid plastic down on top of the base support timber. Cover with a layer of polythene,(The old number plate I used had a polythene backing on it). (Return to Catapult Home Page) (Return to Repairs and Mods Page)

Lay the damaged area of your foil flat over the top of this. Leave 50mm or so of the rigid plastic underneath exposed. (See the bottom rigid plastic layer in Fig 5.) Pour an estimated amount of resin into an old saucer or dish and add the correct amount of hardener. Less if it's hot weather. Mix quickly. 1. Brush some resin onto the damaged areas and lay the smallest pieces of matting on them. Overlap the dagger-boards trailing edge by approx 5-10mm. 2. Brush extra resin on. Stipple to wet the matting and remove air bubbles. 3. Place the larger sized pieces of matting on next, again overlap slightly. 4. Add more resin and stipple again. You might need to hold the pieces down while stippling. Use a rod or nail. 5. Lay some pieces of polythene on top of the repaired areas. 6. Lay a piece of rigid plastic sheet on top of the polythene pieces. 7. Now gently lift the dagger-board, complete with top and bottom rigid plastic sheets, off the bottom board. 8. Keep them held together and turn the whole lot over so that the top rigid plastic sheet is now underneath. 9. Gently lift off the top rigid plastic sheet and peel off the temporary polythene pieces from the upper surface and bin them. 10. Repeat operations (1 to 6) on this new top side until it's level with the main undamaged surface. (If it's a little high the surplus resin will squeeze out). 11. Now lay a sheet of non stick rigid plastic on top. (The number Plate in Fig; 5). 12. Place a weight on top to provide continuous pressure. Leave to cure as in Fig 5. Check there are no naked flames about, then before the unused resin starts to gel, clean your tools and mixing equipment with acetate or thinners.

Fig 5. Heavy weight left in place while resin cures.

When the resin is fully cured, remove the weights and boards. Carefully remove the rigid plastic sheets. These will tend to stick. You should now have something looking like Fig 6, but with a hairy tapered edge of glass fibre matting.

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Carefully cut off the overlapping resin and glass matting with a fine toothed hacksaw. Leave about 3mm of waste still on. Rub down most of the remaining waste with P40 course production paper wrapped around a short off-cut of planed timber (sanding block). Only rub along the line of the trailing edge, not across it. Stop when about 1mm short of the undamaged trailing edge, then change to finer P80 production paper to take the final waste off. Don't overdo this as the thin edge will rub down very quickly. With luck, the repair should now look more like Fig 6. Rub down both sides of the repair using P40 paper wrapped around your sanding block to achieve a level surface ready to apply a coat of body filler paste. You'll can't avoid rubbing onto undamaged areas each time you fill and Fig 6. rub down. Those small chip repairs will end up covering half the foil area !

It's just hard work from now on...

Filler Paste:- Like the resin, filler paste dries quickly, so don't hang around too long once the hardener's been added. Follow instruction on the tin regards mixing. Never use the supplied spreader to take paste out of the tin. Use a dedicated knife that won't touch anything that's got catalysed resin on it. Otherwise your tin of filler will go hard or develop lumps in it.

Blow or wipe any sanding dust off the foil. Apply the filler paste quickly using a wide plastic spreader (usually supplied). An initial thin coat pressed in hard, followed quickly by a smooth single Fig 7. A coat of filler applied after rubbing down the thin layer spread in one even moulded resin and fibreglass. action. Clean the spreader with acetate after each use. This should produce a fairly smooth surface that won't need too much further dry rubbing down. Repeat on each side of the foil. Don't be tempted to rub down freehand.

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Fig 7 shows the first coat of filler paste applied. Don't expect anything looking too great just yet. Especially if this is your first time with filler. Leave to fully cure. You now need slightly less rough production paper (P80) Use with your sanding block to rub down dry again. Occasionally stop to inspect how it's progressing by laying a straight edge over the area. Look for hollows or humps. I use a plastic ruler on edge across the repair to mark any low points with a pencil. Then fill in the low areas.

Keep filling and rubbing down until you are satisfied that you have a level surface. Moving on to the wet stage – You'll need 400 grade “Wet or Dry” paper, used wet. Dunk this in clean water and stroke it lightly on a block of soap occasionally, to stop the paper clogging Fig 8. Again, don't be tempted to rub down freehand. To see how it's coming on, wet the surface and look for undistorted reflections on the surface when looking towards a window or light source. You can change to finer (600 grade) “wet or dry” paper as you get nearer to the finished smoothness, but 400 grade will be OK for this job.

Fig 8. Wet and Dry paper on some old softwood works well.

Fig 9. Foils drying off.

Fig 8, shows how it looks after the wet rubbing. Yellow is the base material, white is the old paint, green is the new filler. Don't be tempted to rub down freehand until the very last stage if you want a smooth and level finish. Rinse off and air dry Fig 9. Now it's ready to spray on some primer. (Return to Catapult Home Page) (Return to Repairs and Mods Page)

Painting. If you don't have previous spraying experience, this type of job is a good introduction to it. The inevitable runs or 'dry' finish won't matter for this work. Suspend the foils via at least two wires each from your workshop roof leaving room to work around them. If you removed the foils from the rudder stocks or handles, attach suspension wires from the original Fig 10: Finished rudders-well worth the effort. screws, put back in their holes. If not stripped down, mask off the parts you don't want painting, then suspend on wires. Apply plastic primer spray paint as per instructions on the can. Note: Brush application of oil based exterior undercoat and gloss could be used instead. But extra days are required for drying in a warm dry area. After the Plastic Primer coat has dried, apply a couple of coats of Cellulose Primer/Surfacer from your spray can, or a 50:50mix of cellulose paint to thinners if using a spray gun. Leave to dry. (Follow instructions if using the spray cans). I will assume

that if you have a spray gun, it came with some basic instructions regarding paint and thinner viscosities, spraying pressures, gun settings and application etc.)

Spraying Cellulose Lacquer - The first coat should be in the form of a light mist, applied with the gun or can held well away, so that the individual droplets don't quite join up on the surface. This will help to prevent the next coat from running. Subsequent coats need to get progressively wetter. It's a learning curve that gets easier the more you do. Getting the surface wet and half lapping each gun pass is a bit of an acquired art. Leave any runs to dry thoroughly before rubbing out with wet and dry paper, again used wet around your rubbing block. Learn from your mistakes rub down when dry and try again, or give up and brush on oil based domestic gloss. When fully dry, unfasten everything and rub down with 400 grade wet or dry paper used wet. Don't rub down free hand, except very lightly. Keep away from the sharp trailing edges or you'll remove all the paint there.

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Hang the foils back up (wear clean gloves) and rub down all surfaces with a tack rag. Apply 3 coats from the spray can, or a 50:50mix of paint to thinners in a spray gun. Leave 30mins minimum drying time between each coat. Apart from leaving to dry, and refitting handles or rudder stocks, that's it! Fig 11.

Fig 11: Repaired foil from Fig 1

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I hope this article may be of use to anyone using fibreglass for the first time. Please let me know if there's anything you think is unclear, or that could be improved. Enjoy sailing your Catapult

Syd – Sail No. 506

END

First published January 2014 Updated December 2016

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