Building the Hull - Previous Page
Picked up the hull from Bloodaxe today. Not the day to do it - it snowed today. You have to understand the English attitude to snow to understand why this is an issue - as the late great Sandy Denny wrote "They said that it was snowing/in astounded tones upon the news/I wonder why they're always so surprised/'cause every year it snows". Anyway English roads descend into chaos - it took 45 minutes to get off the car ferry onto the Island because all the artics (semi-trucks to you Americans) were getting halfway up the hill out of the ferry port and sliding back down again. We wrapped the boat up in polythene sheet with lots of parcel tape and I headed back. At Portsmouth I stopped to buy more parcel tape and wrap it up again - properly this time! Anyway, time I got down to some work. Trouble is the list of domestic jobs that "you've got to do before you start on that d*** boat" seems to have increased rapidly.
While I was in Cowes we stopped off to look at Avenger, Uffa Fox' revolutionary International 14 from 1927, generally regarded as the first planing dinghy. She's on display in Cowes Library, and well worth a visit. Its interesting to note how hull shapes have evolved from what was most definitely the state of the art 14 footer 70 years ago, to what I would like to think is a state of the art 14 footer now. The first thing that strikes you is how full the bows are. Even though the design waterline seems to have had a straight entry this is partially because there is so much rocker forward. Having said that though I think its likely that the bows have distorted over the years - there's a sort of knuckle in the section that is absent from all the drawings of 1930s Fox 14s that I've seen. Amusingly the knuckle makes the bow section look something like that on Andy Paterson's most recent Cherub design! The other big differences are that there is so much more rocker, the waterplane is distributed more towards the centre, and the transom is narrower.
The other thing that strikes you is how incredibly complex - and presumably expensive - these boats must have been to build. She's planked over what must be hundreds of tiny - ½ inch by ¼ inch ribs, and below the waterline there is a transverse plank between each rib - thus running at 90 degrees to the main planking. All is fastened with tiny nails, clenched on the inside. Still, I guess it was worth it - Uffa is in print as saying that Avenger's hull as built weighed 190lbs, and there are all too many classes that make that look light even today with the incredible advances in materials.
I was once privileged to meet a gentleman who had crewed in Avenger, at the UK Dinghy show some years back. He was a kind of guest of honour of the RYA. Anyway it seems that age had done nothing to reduce his concept of what a boat should be like. I was on the Cherub stand, and I seem to remember a conversation that went something like "All these boats - far to d*** heavy. How much does this one weigh? 110lbs? That's more like it." Its all too easy to forget that the people who were involved with these historic boats were probably far more innovative and dismissive of "Its always been done that way" than many of us in the true development classes are now!
[Email message]
"I'm racing ahead now.... foredeck on, glass tomorrow, tunnel on and glassed today. I've fitted the c/case at the back of the slot, and filled the front with the 30mm foam, and glassed over. ( parcel tape + wax on top surfaces, so inners not bonded to top skin). Cut top and bottom glass skins in board shape to fit board. If you need to adjust position, will have to cut away top skin ( ie open the slot,) remove foam, slice as reqd, and refit in new position. ( and glass over to hold every thing in ) But the board should be in the right place for the first rig if its raked right. ( ie lots! )"
The reference to the daggerboard case is part of the change proofing I'm trying to build into the boat. If it ever gets a jib, or some other radical change in the rig then the board position might need changing. If its solidly located in position then this would mean major surgery. Consequently the dagger board case itself is getting on for two feet long, but the daggerboard itself fits into a sort of "cassette", which, if the need arises, could be moved forwards as described without too much drastic surgery.
I've just been down to pick up the bits and pieces to make the wings. For various reasons I had to go down by public transport and via a shop in a town some way off the route. The eventual journey ran to 8 train rides, 3 bus rides, and a return trip on the hydrofoil! The look on some of the various transport staffs' faces when greeted with a passenger carrying a 8 foot by three foot parcel of bits of boat as hand luggage was also entertaining!
Anyway, the false floor is in, and the whole thing is making excellent progress. I think it will probably be at the stage where I will be taking delivery of the part-complete hull to finish around Christmas time. I have to admit that I'm mightily impressed - and also a little daunted - at the standard of work that Andy Paterson has done on this boat. Its going to take a lot of effort on my part to get anywhere near it, even without time constraints. As to when I finish it - well, I've always said that my target is to be on the water by September!
The next stage, of course, will be the mast…
Andy has been making progress on the false floor and bulkheads. These fiddly jobs always take more time than you'd think compared to the main hull. He elected to make a jig for the false floor and vacuum bag it. This saves weight and adds strength against the usual thing of glassing one side and dropping it on top of the bulkheads, but requires better planning and measurement. Its more convenient and less hassle for the pro, but I have my doubts as to whether it would be the right call for an amateur building their first boat. All the main bulkheads and so on are made, its just (just!) a question of fitting them in now.
I went down to the Island last Wednesday (15th October) to pick up the mould (I'm going to store it for a while in case anyone else wants one) and to make decisions about the internal layout. Unfortunately I forgot to bring a camera, and so there are no new photographs. The internal layout will be the simplest. A false floor running from transom to bow, running from the join with the flares and dished in the middle, about 260mm in way of the centreboard case, and about 25 mm at the transom. There will be a low raised triangular brace for the daggerboard case, and a front bulkhead and foredeck. The foredeck runs out across the flare, and this forms a box section for the main rig loads. The daggerboard works out amazingly far aft when you are used to two handed boats, and accordingly it looks as if I shall be building a rudder gantry to give a bit more leverage and control for the rudder.
I'm really happy with the look of the boat thus far, it looks sleek, quick and radical. Judging by the interior layout Andy mocked up out of cardboard there will also be about enough room inside for a family of four to have a picnic! I only hope it looks as clean and neat with all the bits on. The other, increasing, concern is actually sailing the thing! Its going to be, in certain conditions, a substantial boat handling challenge, and in some ways will be appreciably trickier to sail than a Cherub. The bigger rig, which will make it overpowered a lot of the time will certainly add to the challenge. On the other hand there's no way it will be as difficult to sail as an International Moth, although that's not necessarily that encouraging!
"The shell is done! :-)
And off the mould . Weight is 27.5 kg (oops ) but this includes ~1.5kg of peel ply and the edges are not trimmed. So wt is 25.5kg ish. ( also inc. foam gunwales + carbon ). The weight is usually more than the estimate!" [Extract from email message]
The outer skin is on today . The final layup was the +-45o 300g/m^2 glass with a single layer of 300g/m^2 0o/90o E-glass instead of two layers of 200g. This was after talking to SP, but it also saves lots of time with one extra layer instead of two. There's unidirectional carbon along the gunwale edge, because this is the main longitudinal member in the absence of the box section formed by conventional side tanks.
Andy has some photos of the boat at this stage, so as soon as he can get prints to me so I can scan them they'll make an appearance.
Next is to make a cradle, and remove the shell from the mould. The peel ply will be left on until the filling/fairing happens, ( best when the edges/decks are done.) as it helps keep the hull clean.
Once the shell is out of the mould I can get a good luck at what the boat will look like to sail in for the first time, and it will be time to make some firm decisions about the interior layout. First thoughts on this topic are on the Hull Design page.
"Foam is stuck on the bottom and flares, and the topsides will go on tomorrow, so with a bit of filling & fairing the rest of this week, the [outer] skin should be on next week, and then off the mould!" [Extract from Email message].
In a short delay waiting for the foam to be delivered Bloodaxe have started on the daggerboard. Its Cedar core coated in unidirectional glass in three tapered layers, vacuum bagged for strength and (less) weight. The projected finished weight is about 2.2 kg ( lighter than a 470 rudder blade and 50% bigger). (End of Bloodaxe commercial :-) ). Seriously though that construction can be regarded as mid-tech, which is more or less the theme of the whole construction. In general I've stepped back from the leading edge a bit, as much as anything else for reasons of cost. Amusingly enough the materials are pretty much the same as on my Cherub, built 1979/80, which was much less compromised for cost…
The inner skin is on the mould, and the next stage is the foam.
The materials list for the shell is as follows.
The foam is grid scored around the bow sections to allow for the curvature - the skins are pretty severely 3-dimensional in this region. The reason for using a male mould with a ply skin is that all the skins & the foam can be vacuum bagged on, saving lots of resin & weight . ( perhaps 5-6 kg ) and no bubbles. It also means the foam/ hull can be faired up on a rigid base.- and makes building a second boat much easier should anyone want one.
Outer Skin 1 layer 300 g/m^2 E glass @ 45o; 2 layers 200 g/m^2. Inner Skin 1 layer 300g/m^2 E glass @ 45o Foam 10mm Divinycell H-80 bottom; 8mm H-80 topsides Estimated weight of shell. 24 kg It occurs to me that I haven't actually documented how this thing is getting built. I'm not doing the whole thing myself - apart from anything else I don't have the time. What's happening is that Bloodaxe Boats are making the jig and the shell, and I will do all the fiddly bits and the fitting out. Quite where the break will come depends a lot on how the wallet stands up, but Bloodaxe will be doing at least the main shell and the false floor, not to mention - of course - the daggerboard. The rudder will be the Bloodaxe foil off my Cherub - I don't think I'll be able to sail both at the same time! This is quite a nice split, since the big parts of the job are pretty challenging for someone like me who doesn't work professionally with composites, but quick and straightforward for the pro, and all the little fiddly bits of fitting out, brackets for cleats etc. are horribly time consuming for a pro, but quite easy for me to do an hour or two on in the evening after work.
It strikes me as exceedingly handy that the Bloodaxe should have got an email account just before this project started. We seem to have done 90% of the planning and design process by email They can't be held responsible for the hull shape or concept - I suspect Andy Paterson would have drawn something rather different - but have had an enormous influence on the details of construction and materials, and in fact in making the whole thing a practical proposition.
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· Page Last Updated 23 Jun. 1998