Hi everyone,
Hopefully I have posted this question to the right forum. This is the first time I have posted here, so please forgive my ignorance.
My father and I have been modifying a Hobson Solocraft under the guidance of the designer (Henry Hobson). Solocraft are well respected in Tasmania by cray fishermen, abalone divers and others that expect a lot from their boat. Anyway, because of some health issues in the past, the project has been delayed for a couple of years and unfortunately Henry Hobson passed away recently, leaving us with some missing parts of this design. We have no idea of what has happened to his drawings etc (if any) as we just followed Henry's direction, step-by-step in continuing the modifications that he had begun.
The original 16' boat has been extended at the transom by another 5' using polyester resin, mat and woven rovings, making it approximately 21' overall (6.4m). The glass is 1/4" thick generally, with some areas a bit thicker (keel, chines...). It is almost ready for paint on the bottom and then we will roll the hull over and set about adding some stringers and a bulkhead to the aft section. Henry suggested that he was intending to add a top-hat section stringer. He showed me a rough outline drawn on the side of the boat, but no dimensions as we weren't up to that part yet.
My thoughts now are to add perhaps two top-hat section stringers to effectively divide the aft section into three - roughly 2' wide each. These stringers would be about 8" tall with some laminated timber in the top and ply shear webs on the sides. The intention is to tie the new section of the boat into the old with as much gluing area as practical, hence the choice of top-hat sections, and then add a 3/4" ply bulkhead half way to match the rest of the boat (which only has bulkheads as the box keel serves at an inverted top-hat section stringer). The sole of 1/2" ply can then sit on top of that structure. I am not sure of how thick the ply webs should be, but I would think 1/2" plus. Stringers and bulkheads, corners of the transom will be taped in with 12oz biaxial tape and R180 Epoxy. Any advice or suggested alternatives would be greatly appreciated.
Hopefully the pictures I attempted to attach worked so that the above ramblings will make some sense. The first picture is of the preliminary framework for the extension - male molded like the rest of the boat - and the second picture is of the inside of the extension with the mold removed, well most of it anyway. the rest will come off when we get in there to wash it out.
Hopefully I have posted this question to the right forum. This is the first time I have posted here, so please forgive my ignorance.
My father and I have been modifying a Hobson Solocraft under the guidance of the designer (Henry Hobson). Solocraft are well respected in Tasmania by cray fishermen, abalone divers and others that expect a lot from their boat. Anyway, because of some health issues in the past, the project has been delayed for a couple of years and unfortunately Henry Hobson passed away recently, leaving us with some missing parts of this design. We have no idea of what has happened to his drawings etc (if any) as we just followed Henry's direction, step-by-step in continuing the modifications that he had begun.
The original 16' boat has been extended at the transom by another 5' using polyester resin, mat and woven rovings, making it approximately 21' overall (6.4m). The glass is 1/4" thick generally, with some areas a bit thicker (keel, chines...). It is almost ready for paint on the bottom and then we will roll the hull over and set about adding some stringers and a bulkhead to the aft section. Henry suggested that he was intending to add a top-hat section stringer. He showed me a rough outline drawn on the side of the boat, but no dimensions as we weren't up to that part yet.
My thoughts now are to add perhaps two top-hat section stringers to effectively divide the aft section into three - roughly 2' wide each. These stringers would be about 8" tall with some laminated timber in the top and ply shear webs on the sides. The intention is to tie the new section of the boat into the old with as much gluing area as practical, hence the choice of top-hat sections, and then add a 3/4" ply bulkhead half way to match the rest of the boat (which only has bulkheads as the box keel serves at an inverted top-hat section stringer). The sole of 1/2" ply can then sit on top of that structure. I am not sure of how thick the ply webs should be, but I would think 1/2" plus. Stringers and bulkheads, corners of the transom will be taped in with 12oz biaxial tape and R180 Epoxy. Any advice or suggested alternatives would be greatly appreciated.
Hopefully the pictures I attempted to attach worked so that the above ramblings will make some sense. The first picture is of the preliminary framework for the extension - male molded like the rest of the boat - and the second picture is of the inside of the extension with the mold removed, well most of it anyway. the rest will come off when we get in there to wash it out.
?? it could be a real speed killer as the back end of what you have will cause drag and suck the boat down a little !! into the water:?: But you never know !! might be wrong !! 
