Ok here it is you will need some good ply 19mm thick and 10 to 12 veneers dont use three ply or five ply !!
The amount you need is about 300mm x 100mm go to the local boatbuilder nearby and ask if you can grovel a bit from his rubbish bin (we throw out bits ten times that size every day)
On your ply draw a straight line with pensil get a hole saw with a inside cut width of around 45mm
Cut three shallow cuts
Once done mark in ten mil from each side of the cut this is where the fin slots start and finish
Next you route out the finslots I use a makita trim router which has a adjustable angle base this i set up to the cant angle i want
Nail a small piece of timber to the ply as a guide for the router edge to run along
Now you can take one of two paths next quick and simple or a bit longer and better
You can just route out the slot with a 6mm bit and your done simple but it wont last as long
the better way is to route out slighty over width resin fill then reroute out to the 6mm
You do need to resin fill the screw holes any way
these holes need to be about 9mm long and wide enough to fit a 4mm screw with a countersunk head
So drill these out first over size include the counter sunk bit ,the aim is that after they have been filled and then redrilled the screw will only be touching hard resin not the wood
You will have noticed that while i was back filling with resin i also cover the top with a layer of glass
The next step is to route out the fin slots with the 6mm bit dont forget to set the angle up right,bout of the side ones can be done the same way later you just turn it 180 degress dont forget to do the back one at 90 degress
All so drill out the mounting holes and counter sink,see the way they are laid out in the pic so one can turn 180 degress to make a handed pair
The back one has no allowance for adjustment
Make a paper template of the placment of the holes so you can reproduce it when you make plugs with different cant angles
Now cut around the outer cut ring with a jig saw
cut one silghty bigger2-3mm then set up the table on the face sander to three degrees sit the cut plugs base down and sand them inti the inner edge of the cut line
Sand the one you cut slighty bigger so that it is about 2 to 3 mm bigger but still with the three degree edge ,we will sand this one down again later
You now have plugs lets make something to put them in
Take a piece of solid wood and route out a hole about 48mm wide and 20mm deep do this three times
Get some builders bog that stuff that goes off real quick,smear it round the
egde of the hole,get the plug that is over sized and place it on some gladwrap twist it tight on the top and push it in the hole ,put a clamp on to hold it down
This will form the inside of you socket mould
When its dry pull it out and do the same with the other holes
You can now sand that one down the same as the others
If you now drop one of the plugs in the hole there should be a 2 to 3mm gap all round
Get some 4 oz glass three layers put it over the hole and push the plug in ,it should be a snug fit trim the glass then cut some for the other plugs
Stick some glad wrap over the hole then prewet out the glass put it over the gladwrap then cover the plug with gladwrap just like before
Now push it in the hole and clamp it down
Once its in the hole open up the glad wrap and push it out that will stop the resin going down the holes and amke it easier to get the plug out after its dry
Remember that step because it the same when you put the socket in the board
Right when its dry pull it out and trim it up ,make sure that the plugs fit the sockets sand them on the face sander gently to make them fit
Now we need to set in the grub screw holes to hold the fins in the plugs
I have found that casting these in works better than tapping them
The whitish stuff in the photo is plasticine which i use to stop all the resin from running down the holes where i dont want it to go
The trick I have found when casting is to first make sure that the bolts used are well coated with some sort of non stick (steal one of those cooking sprays from the kitchen)
Then mix up a small amount of resin in a plastic container sneak into the kitchen again and microwave the resin for about 8 seconds then run like hell back to the plugs before it goes off pour it in the hole and set the bolt in ,the plasticne in the fin slot holds it well
Why microwave the resin?when heated up it goes very runney which is perfect for getting into the fine thread on the bolt
Well now thats all done you had better return the gladwrap and spray or you wont get any dinner!
To attach the plugs to the sockets ive used two different methods one is to cut a small strip of alloy and glue it to the underside then drill and tap it
This works ok but you have to make sure that you allways put some isolating compound in the hole so the ss screw does not react with the alloy
The other way is to fully install the socket in the board then drill a over sized hole and cast the bolts again ,ive had no problem with this .
To set the sockets into the board measure place as you usually do cut out the hole with a router make sure that you under cut the foam around the
hole so you expose the under side of the glass about 2mm then dig down to the deck skin on the rail side and the inboard side a small hole about 5mm diameter
Smear round the hole with a resin glue fiber mix and push the socket in with the plug wrapt in gladwrap ,push it down till its flush fold the gladwrap out so the glue doesnt get on the plug and weaight it hold it what ever untill its dry
Now if you used the alloy tapping plate dont forget to line the fin up so the best position gives you adjustment each side
This can be done later if you are casting the bolts
So at last you now have a fin system that lets you fine tune your board
and the best bit is you did it all your self
go to the next post for one final pic