Only For Nutters – Part 9

I was not exactly overjoyed when the Editor decided to call my whole series of articles ‘Only for Nutters’, but this month I am coming clean on the many changes I have made to the original plans. You can decide whether I have taken leave of my senses or not!

A yacht club acquaintance once cautioned me about making even a small alteration to the specifications in plans, on the grounds that even one change may have a knock-on effect and result in lots of extra work. Of course he was right, but I went ahead anyway and throughout the building process I have had to make new calculations, and even produce about a dozen of my own drawings. The danger is that when you stray off the track you become responsible for the design and cannot expect the designer to help you out of a pickle.

The first change I made was when I chose to lengthen the boat by 2ft. At that point I opted to keep everything else pretty much the same. The reason for adding the extra was firstly sentimental (I wanted the new boat to be 1ft longer than my previous one), secondly to get a little more accommodation space, and thirdly because stability increases with the cube of length, so a boat 10% longer has 27% extra longitudinal stability. I was interested to read that Erik Lerouge considers adding a little extra length is a good move (MR issue 09).

It was not just a simple matter of putting in an extra central section (didn’t they once cut ENZA in half and add a bit to the middle?), but of expanding all the dimensions in proportion, which would inevitably mean altering the rig sooner or later. To get the cockpit space I wanted I also moved the aft beam back a little, which affects the mainsheet track location, and so on…

Then, even before starting the build, I had a complete rethink of the accommodation layout, largely influenced by my daughter’s reaction to seeing the layout of a Maldives. Nothing short of a bridgedeck saloon would be good enough! Suddenly the original plans with shelf-like double bunks in the low bridgedeck just looked like a poor use of space.

So the bridgedeck cabin was born. After looking at many styles on similar boats I am of the opinion that full standing headroom in the bridgedeck on a boat this size is too much. The ones I have seen either have very low clearance above the water or look boxy and out of proportion. It would have to be stooping headroom. To cheat a little I lowered the saloon floor by 150mm, to give 750mm minimum clearance above the water, and under the saloon seating I sloped the floor gently upwards towards the front main beam.

All was fine until my dear wife insisted on a section with standing headroom ‘so you can take your oilies off’. I know when I am beaten, so a small raised hardtop section has been added to the back of the cabin. It is well-curved and I hope it does not result in the boat looking too high.

All this meant shifting the double bunks into the aft hull sections, which were of course too narrow, so an underwing flare was added, built up with cedar strip. Just doing the hull flares took an extra 4 weeks. Inevitably design changes take a long time as you have to proceed very carefully.

Well-rounded shapes seem to be the secret to an attractive design and are aerodynamically far superior to squared-off cabins. They are also far harder to build. I described in the last issue the making of the mould for the cabin, and just now we are finishing off making the various roof sections in balsa composite…

At this point I just want to expand a little on the last sentence. How easy it was to write! But it disguises some incredibly hard work. There is absolutely nothing in my experience so agonising as working against the clock laying up and squeegeeing great areas of glass and resin. Only yesterday, after taking the morning to set up, we toiled for six hours non-stop to get the front section done. By the end (7pm) my arms ached like nothing else and my legs would hardly straighten from crouching on the raised platform. Andy had to scrape accumulated gunge off his knees! We staggered home for a beer and a bath…oh, bliss!

Before the mould is finally dismantled (from underneath the joined-up cabin roof) some bits of it will be cut away to enable us to tab together the underside of the roof sections. When they are finally joined the curves should blend in well with the rest of the boat. Reinforcement will be added for tracks, winches and stoppers, but the great compression strength of endgrain balsa means that the core does not have to be ground out, a particularly helpful feature for eyeball boatbuilders.

One of the features of CUD (that’s Computer Unassisted Design) is that you often need to try things out in mock-up. We made a representation of the cabin doorway and step-down to check for trip hazards, and I have been sorting out the optimum winch location by trying it out with a paint tin and a stick! The designers by no means get everything right, and if you are building a boat for yourself you might as well be sure that you can reach things comfortably.

We have not yet decided on the shape or position of the windows, these will be decided using black paper cut-outs until it looks right. I greatly admire the curvy shapes that a designer like Darren Newton puts into his windows, some others seem to have been inspired by car window design, and it is clear that, just as with a house, well-proportioned windows can greatly enhance the look of any boat. (The reverse is sadly also true.) Windows, toerails and paint stripes are all elements that help to disguise the height of the superstructure.

I have been keen to incorporate some other good ideas that come my way. One from a friend seems really neat. This is to have a hatch mounted either side of the mast, effectively forward-opening windows in the bridgedeck cabin. It will then be possible to perform all the operations needed at the mast by standing in the hatchway, without having to go outside of the ‘safe zone’. To achieve this some internal rearrangement of the settee, perhaps with a removable backboard, will be necessary. As this has only been sketched at present, it will need some detail design work. Of course one can still go around the outside of the cabin to the mast base and reef etc. from there. But as I am not a fan of guardrails on cats – they are ugly and mostly just make docking harder – the idea of being able to pop through the cabin to tuck in a reef seems attractive.

The mast itself is another departure. The original design called for an alloy rotating mast, but having looked into the possibility of constructing my own, I have been seduced by the prospect of making my own ply/carbon mast! Once again I am pleased to find my hunch backed up by an eminent designer like Lerouge. Unfortunately the plans that Kurt Hughes sent me were hard to understand, so I sought some further advice. Nick Barlow has constructed over 20 wingmasts, and he was able to give me valuable help with the construction method, carbon layup and many other details.

Having a composite wingmast and a lengthened boat means that the rig dimensions have to be changed accordingly. With my revised drawings I can now approach sailmakers and get the mainsail ordered (this autumn to take advantage of the seasonal discounts).

I do not wish to give the impression that these alterations are being carried out without any proper consideration for first principles or technical things like the balance of the boat. There are plenty of books on naval architecture to help with every aspect. The challenge of redesign is first to work out why the designer did something, then to see if the modification affects strength/balance/ rigidity etc. and whether they can be compensated for. As many details were left off my plans there was always a certain latitude, for example in siting the batteries, to allow for sorting out the fore-and-aft balance. A professional boatbuilder told me how he weighs every single thing that goes into a boat in order to calculate precisely how she will float. I could not bring myself to attempt anything so tedious, but have a spreadsheet for the heavier items so I do not get it wildly wrong. The rest will be down to tuning.

Other smaller design changes involve fitting 2 Yamaha 9.9 outboards on swing-down mounts. I have hummed and haaed over one engine or two for months, but have to admit that it was never fun at close quarters in my previous boat. It was extremely tricky to manoeuvre with a single engine, and the greater windage of the new boat would only add to difficulties. So the outboards will be slung in streamlined pods under the aft corners of the bridgedeck, swinging down for motoring and tucking neatly away for sailing. This is really just an improvement on the original design’s pair of 6 HP outboards (I could not find any with remote controls) and ladder-type mounting.

I cannot imagine anyone undertaking the enormous commitment of building their own boat and not making any design changes at all. For me it is one of the great pleasures of the task. Everyone has a different idea of what makes the perfect boat, and how they like to sail. I have been on plenty of boats with features that I would have changed immediately. Building from scratch offers the opportunity to try out all those design ideas collected over the years. Of course there is a risk that it might not come out well, but in the end that is a test of my craftsmanship. If it turns out to be a ‘dog’ then I have only myself to blame. But generally with boats “if it looks right, then it probably is right”.

I do find that I have to be obsessive about detail. Take Perspex windows for example. They have a different expansion rate from the structure around them, and have to be fastened with care. Just screwing them to the outside of the cabin looks crude. The neatest attachment I have seen was on an Open 60, where the windows were recessed flush into the cabin roof. I cannot remember whether there were even any screws. There is a danger that the sealant under the plastic will show up any airbubbles, so the underside of the window has to be coated first. Then the edges have to be meticulously sealed. The whole operation has to be spot-on to work properly. Forum discussions can be very instructive because one can compare other people’s experience with various products and processes.

Working on this boat has been my constant occupation for several years now. When I am not at the workshop, I jot down notes in a notebook and sometimes worry away at a question for months until I find a solution. I have to admit it borders on obsession, but working so hard at it is surely the only way I am going to get my dreamboat right.

Nutty? You be the judge…