Pattern Madness!!! Please help :/
21st April 2015 at 6:13pm #1250HoofheartedParticipant
Hello OK enthusiasts,
So you might have seen my earlier building post, the ball is now rolling! I have the plans now and also the measurement rules too. Happy days
I am currently taking the measurements from the plans and making hardboard templates, I have got to marking the curvature of the underside of the hull on the transom and using a pin and batten technique I though I would get the perfect curve…….Mmmmm I was wrong it schemes. So in the picture you will see the method I have been using, the problem being that the batten doesn’t intersect the top points of my lines! Yes I have taken into account the thickness of the batten and adjusted the pins accordingly (i.e moved them down the thickness of the batten).
Short story it hasn’t worked please help with how I should combat this or another solution.
[attachment=0:x1y92ndq] 11175054_10153266895703464_6475940392329835460_n.jpg [/attachment:x1y92ndq]22nd April 2015 at 11:53am #8241Bill BParticipant
This could be because you are trying to make a transom with – effectively – a flat panel at the centreline. The drawings are for two flat panels on the bottom of the boat meeting at a V in the middle. There is then a tolerance for the position of the chines and centre from an imaginary base line and a maximum amount of curve in each panel. Even with max curve – I had in mind that the panels still form a slight V at the centre.
One of the problems you may have if you are trying to build a boat with max curve in the bottom panels is that the curve is compound as you go down the hull and you could have problems making your plywood follow this curve.
As an aside , The Millican boat I had years ago was max curve on the bottom and I found it very hard to sail fast and it was very wobbly downwind.
I understood that to get a decent planing hull, you would try to make the rocker (keel) as straight as you can and get the chines as straight as you could. Someone will definitely have a theory that is different to this.
Bill23rd April 2015 at 5:26am #8242DaveBourneParticipant
from doing a fair bit of work on the icebreaker hulls it looks like the v at the centreline of the panels is pretty shallow and only starts to curve up to the chines about a third of the way out from the centreline. Again, Bill’s right, the keel rocker is as straight as possible between the transom and st3 to give a flat run for planing. If I were to build from scratch I’d be looking at making the boat as stable as possible ie: panels with little curvature and as flat as possible between transom and st2. Straight chines, with as fair a curve as possible. Maybe wide at the transom ( although may be a bit sticky in the light), middle at st1, narrow at st2, mid at st3 and trying to continue as straight as possible to the bow to give a long waterline. Others may have a completely different idea!! Your choice23rd April 2015 at 5:56pm #8243Bob BourneParticipant
where DO you get your ideas from? :roll:23rd April 2015 at 8:15pm #8244DaveBourneParticipant
says the man who built a boat so round you had to bounce it rather than sail it!!23rd April 2015 at 9:05pm #8245HoofheartedParticipant
Thanks for all your advice, I have overcome my curvature issue with the batten by applying small amounts of pressure to the batten ensuring that it meets the correct measurements at the right places. It schemes to have worked. On the topic of curvature of the bottom of the hull, what you see in the drawing is an exact replica of the plans and I will be increasing this slightly to reduce waterline. Currently with a straight edge the max curvature is 7.5 mm, you can plus 15 mm onto this if you fancy, but thats too much for me. Having studied my dads OK (1971) all be it slightly older that has 10 mm curvature on the hull so I was going to stick with this. Whats your thought?????? Too much or not enough???????
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