Saturday, February 1, 2014

The designing process.

An offhand remark or two and a couple of subtle roundabout questions and we (Donna & I) had found our designer for our next trailer sailor build.
I don't want to go calling this design a sportsboat as neither my wife or the designer want to race in the sportsboat class. This design may or may-not end up being fast enough to qualify as a sportsboat and we don't mind either way.

The design was for a 20ft long hull so we would qualify for the local one-up and two-up shorthanded races which have a requirement for 20ft minimum hull length. The other requirement was it had to be much more efficient to windward than our previous build Shazza which was an i550. The new design has a much more refined bow and, for the front 1/3 of the boat, there has been an interesting discussion of compromises for windward performance and down hill raw speed, the result being a forward area similar to a Cherub or NS14 dinghy to be build from ply and strip plank cedar. The rear end of the new design is basically the same as the i550 but again a little more refined and tweaked while allowing for ply construction.
Currently the designer has a polystyrene scale model that has just been finished to stage 1 knowing that I would want to tweak it somewhat until we're both happy, I just saw the model for the first time today after waiting almost three weeks for the designer to have time to construct it. I wont show the stage one model as it does not reflect well on what the finished model will look like and may cause some people to go running for their lawyers to start litigation for design/copyright infringement. Lets just say the end result of the modeling then build will be similar to other designs but will be obviously unique in its own regard.....I'm having great difficulty waiting for the finished model myself !

The shortlist of requirements for the new design came about through personal experience from boats I've sailed on and built. This list obviously suits what we want out of a trailer sailor and would not be to everyone's taste. The Croft 6 is a one off boat for this very reason, we didn't want a boat off the shelf and this way we can also spread the cost over some time and end up with a new boat exactly to our requirements.

The shortlist for us is.
- 20ft/ 6metres
- furling headsail (Open 650)
- bulb keel           (Open 650/Shaw 650/ i550)
- retracting spinnaker pole (Shaw 650/Open 650)
- mast head spinnaker (All sportsboat/fast trailer sailors)
- cabin big enough to cover the requirements of the trailer sailor association (i550)
- built in area for porta potti and lee-cloth bunks
- transom bridle for main sheet system (Open 650/Leach 650)
- built into cockpit floor ice-box  (Shazza- i550)
- boom tent            (Shazza-i550)
- tall straight mast for easy hoists & drops

Possible and still up for discussion
- knav vang  (Viper 640)
- spinnaker chute, external (Seascape 18)
  

From our experience with Shazza (i550) neither of us wanted to be going forward to get headsails up or down or mostly out of the water so we're going for a furling system.
The bulb keel is the most efficient system, we did however have a lot of raising and lowering issues with our i550 which we will need to over-come with the new build.
We found the articulating spinnaker pole very good on our i550 but versus the drawbacks of the sheeting and rotating system not always being user friendly under pressure we are opting for a fixed position retracting pole this time round which will have an internal drain to keep water out most likely through a drain hole through the hull skin--to be sorted.
The main sheet system is being kept simple and cheap by having no traveler, just a bridle system off the transom (18ft skiff style of main sheet pulley system with a final ratchet block from the center of the cockpit sole. This should also allow us some more potential sail area with the longer boom---remember this is a one of boat, we are not restricted to any rules.

Basic specs will be;
LWL               6.00
Width             2.45
Depth             0.20 / 1.50
Lead Ballast   100kg
Mast               8.50
Boom             3.50 --ish
Spinnaker #1     50sqm-- ish
                 #2     30sqm --ish

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