Advice required on MK 1 floorboard creation
21/03/2020 at 2:55 pm #20013
We’ve decided to make some floorboards for our MK 1 GP14 as it currently only has the base hull floor and we are fearful of damaging it this season. I’ve found the references in the rules regarding board widths and it says the minimum is 300mm and maximum is 380mm. However at the back of the boat the width of the floor is around 127cm, which will mean the 380mm maximum boards will not cover much of the floor.
Also I’ve seen mention of 2′ x 4′ boards being used, but the available floor space from front buoyancy tank to the transom measures 278cm, whereas an 8′ board is only 244cm long.
There are 2 blocks on the floor (one either side) which the boards would sit on and have turnbuckles on them, and a block at the centre of the rear floor which also has a cleat for the elasticated cords from the plastic flaps over the 2 scuppers.
Should I use 6mm plywood with width wards battons underneath, with one board down each side of the centreboard casing, meeting at the back on the rear block? Is marine ply essential or is well sealed and painted regular ply sufficient? How far forward should the floorboards go? Level with the front of the centreboard casing or further forward?
Any advice would be most appreciated, as we can then get on with making some templates, test fitting them and then purchasing the ply and getting on with the job.
Many thanks in advance
21/03/2020 at 3:59 pm #20014
Have a look at the discussion which is (at present) two strings down from this, “Old Fibreglass Boat”. Part of that deals with floorboards.
Steve White is our resident expert on the early GRP boats.
Fitting effective floorboards is vitally important, not least because the GRP hull was never designed or intended to take the localised weight of a person standing on the hull skin, and it may not be strong enough; the load needs to be properly spread. Having said that, unless you intend racing the boat at the highest level of competition, which is probably unlikely for a boat of this age, my own personal view is that I cannot see anyone seriously objecting if your floorboards are wider than the Rules permit.
And I would also expect that the 380 mm maximum width is for each side of the boat separately. The normal arrangement is to have the floorboards in the centre of the boat, extending out approximately as far as the side buoyancy tanks, and with the outer edges continuing in much the same line as far as the Mk 1 stern tank. So, on the Mk 1, I suspect that the outermost part of the hull skin abaft the side tanks is not covered by floorboards. I will see whether I can find some photos; if so I will post them later.
Hope this helps
21/03/2020 at 4:05 pm #20015
A recent post “Seeking info on my GP14!” has a photo of the interior looking aft, and clearly showing the floorboards.
This is actually a M2, 2 boat, so there is no stern tank and instead the side tanks extend all the way aft, but I am sure that if you make the floorboards to that sort of pattern they will be entirely suitable for your Mk 1 boat.
Hope this helps,
21/03/2020 at 5:03 pm #20016
There is no problem with an 8ft sheet, the boards only need to go to the forward edge of the aft deck, not all the way to the transom. I have just measured a board I had in an old boat, it looks like 4mm marine ply but I reinforced the edges with strips of 40 x 6 mm. The ply was 1 ft wide ( sorry about mixed terminology) and the reinforcing projected slightly, maybe 5mm either side. Be careful about making them too wide as it can be a bit of a fiddle threading them under the thwart when installing. Well painted and maintained you can get away without marine ply. You will also need a short filler piece between the centreboard case and the aft deck.
Good luck, Norman
23/03/2020 at 12:53 pm #20018
If you have a look on the posts on “old fiberglass boat” I have put on some info about making floorboards.
Hope this helps you !
23/03/2020 at 3:36 pm #20020
“Well painted and maintained you can get away without marine ply.”
I agree, and I will say that if you are going to the effort of making the floorboards, and they are not considered disposable items, then making them from the ply which has waterproof glue and minimum voids is an investment in time sailing over time maintaining.
Grades of plywood are for other forums to discuss at length, but make sure that the wood glue is waterproof.
When I made the floorboards for 9121 (now a training boat at my local pond) I used a big piece of cardboard to make a template, and made the boards out of a single sheet of 1220 x 2440 BPW plywood sliced directly along the centreline, with appropriate stringers. As another poster has said, the floorboard needs to be flexible enough to bend and twist to get over the stern and under the thwart in an action which very much suggests that once fitted will stay in the boat.
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