Ply epoxy daggerboard, edge, repair

simonfraser

simonfraser

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The aft edge of my dagger board has split, not near the end, by repeated bashing into the casing.
(Something else to fix now I an aware of that problem)

The split is over 30cm, it appears the board is sheathed.

I guess I could run thin epoxy into the split, press it back together again and sand / paint it ?

Never done this before, what is the best runny epoxy, how to stop the wood I am going to clamp it with sticking to it ?

I have seen epoxy 'beads' used to thicken, so could use that on the relatively small parts which are now missing ?

What hand tool is best to grind down the set epoxy ?

Many tnx :)
 
Basic unthickened epoxy is quite runny. Your proposal might work, but you need to perhaps open up the split a bit first, fill it and then clamp. Wrap your pads in parcel tape to stop them sticking. You can get a lightweight filler that is easy to sand with 120 grit - suitable for filling dings and surface scratches. Everything must be dry and clean for it to cure properly. Have a look on the WEST site - lots of good information on repairs and material choice.
 
Get some epoxy with slow hardener, I use West so it is 209. If you only want a small qty try a model shop. I hour at least!

Make sure your board is dry.

Open up the split a little mix the epoxy and warm it up. Stand the pot in some boiling water. The epoxy will get quite runny.

Slosh it into the crack working it in.

Clamp using a HD bin bag to prevent sticking.

After 24 hrs fair any excess epoxy using a surfrom tool. The epoxy will be green at this stage and cuts easily.

For final fairing use the epoxy mixed with microballons or silica. This makes it sand easily.
 
Simon: if there's any gap-filling to be done, microfibres make a far stronger epoxy mix than microballoons or colloidal silica. You say the board is sheathed -- presumably with GRP of one sort or another? Bearing in mind that it's already been damaged despite the sheathing, I'd be inclined to re-sheath the damaged area with epoxy and cloth, then fair. This may require abrading away some of the ply to get sufficient depth in the lay-up.
As said, microballoons are fine for fairing, and much easier to sand than microfibres.
As you've read, parcel tape works fine as a release film on small jobs. For larger jobs heavy duty polythene is fine (but not with polyester resin).
I'd prefer to take the board off and do the job at home, but maybe it's too big for that to be practicable.
 
Tnx mac, the sheathing is split off the back edge. Definately not structural. I faired the board some time ago to stop it humming under way, over 10 knots.
It may crack again if I don't change the way the board is lowered. Basically when it's lowered, whilst going along, the board kicks backwards with the above result, i now realize .....
So I will have to change the tackle for moving the board and somehow stop it from tilting, perhaps check this out with team oracle !!

Anyway, the board is 3m plus, that's not gona fit in my car, tnx for all your input.
 
All the advice so far is good. For sheathing you might try to finbd a bit of kevlar cloth. This is very easily wrapped around the trailing edge but is incredibly tough.
You must make sure that the kevlar will be below any area you want to fair off. It does not take kindly to being sanded. The strands of cloth stick up out of the resin in a horrible way.
Regarding kicking up of the cb. My TS has a vertically lifting CB 100kg of ballast. I fit a locking bolt through the case to hold it down. I foitted a 5/16 whitworth bolt right through the case hard on top of the cb. This is right at the back of the cb. So it can not kick up when I hit something hard. The bolt has been bent a bit a few times but the effect is to help dissipate the energy of the boat stopping. It has reduced damage to the trailing edge on the back of the slot and case. good luck olewill
 
Hi Simon
Does your dagger board go in vertically or at an angle?Mine goes in vertically and has a removable 'crash box' made of foam that is shaped to the trailing edge of the board/case.This gives the trailing edge something to bear against.As for the repair,it needs to be dry after washing the salt out with fresh water.Has your board hummed for a while or has it started/got worse recently?Epoxy is really easy to work with,the stuff I use is from Fyne Boats.Do wear gloves/mask etc.
Cheers
 
William / Caiman, the board drops down through a nearly vertical slot. If I used Kevlar it would have to be faired after, that's more trouble than it is worth.
The supporting line is at the aft end and makes the board tip forward, this contributes to causing the damage at the thin aft end. I will change the lift / drop system.
It's damaged about half way along the protruding part. The supporting part of the dagger board in the slot is not so tapered and has no significant wear.
A better support for the lower aft end would be perfect, for that the boat has to come out.

It used to hum before I faired the sides of the board, which did not stop the vibration after which I tapered all of the aft section.
Not humming now, even with the damage ...

Epoxy ordered.
 
after gluing wood back together with epoxy resin , use epoxy putty to fill and fair where wood missing , its as tough as old boots and will take harsh treatment , ideal where your board hits the casing , i use it on my rudders on cat in similar circumstances also on leading edges and board tips that hit the ground , you can buy on e bay or pay more at chandlers , comes in sticks , that has hardener and epoxy together but not mixed, looks like stick of plastasene , snap a bit off , break up and roll about in your hand until uniform colour , mould and press into place , you can mould into place with fingers and sand after about 1/2 hr after initial cure , note sanding by hand after this is near impossible as it sets rock hard , though machine sanding still works .

Epoxy putty is a fantastic bit of stuff to keep on board , you can fill holes underwater , repair pipes , anything you can think off , even made a breather thing for outboard fuel cap when I lost one , filled very badly abraded (through glass and gelcoat ) transom corner on my Sonata 20" long in below freezing conditions , infact so cold my fingers froze forcing it into place and shape , was worried about adhesion as well out of using specs , but left a fortnight and machine sanded , it didnt budge and has survived a season knocks without a scratch.

i used this :http://www.ebay.co.uk/itm/Milliput-...Scrapbooking_Glue_Tape_EH&hash=item3f2234a4e6
 
I see from your reply that the boat and board are larger that I thought and you are not taking the board home.

How are you going to ensure that the plywood is dried out? This is ESSENTIAL if using regular epoxy which hates damp, will not stick and will not cure properly if it has water in it.
 
Have you considered using carbon fibre? Very strong and light, easy to apply and can be faired but needs a final coat of epoxy.

Also Note: Epoxy resin is NOT UV stable, so consider a dab of Epoxy primer.

Re the comments about poly resin and parcel tape, I use Craft Tape, it has a silicon addative to prevent it sticking to it's self.

Good luck and fair winds. :)
 
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