Half Hull to Plans?

[Spenie]

I'm still looking to find plans for an older Beal Island/Jonesport Lobsterboat. Have had some luck and I thank all those who've helped. Particularly you fellows up in Maine.

I've been offered small model half hull's for some of these boats as a way to maybe get plans. I've never considered working this route before, but what's it take to get plans from a half hull model. Or is it even necessary to get plans? Seems like most of the old time builders carved a model hull and then started building. Anyone ever build a boat from a carved half hull?

[Steve Lansdowne]

Heck, that's the way it was done all the time years ago!

[Jon Etheredge]

Anyone ever build a boat from a carved half hull?I have built a small 13' catboat from a half-model that I carved.

You will need to take off the shape of the sections from the model. There are a variety of methods that can be used to do this:

1) Cut the model on the station lines with fine kerf saw then trace the sections on paper.

2) Built a pantograph type device to copy the shape of the model at each station.

3) Use lead strips or copper wire to pick up the shape of the model at each station.

4) Carve thin wood sheet or card stock to fit the model at each station.

I'm sure there are many other methods besides these.

After you have the sections drawn on paper, you can draw in waterlines, buttocks, and diagonals to suit your fancy. Then use an architects scale to take the offsets so you can lay down the lines full size on the loft floor.

[jwaldin]

I think in John Gardners Dory Book he describes how he took lines off boats he found beached.
Any good machinist can get accurate lines off a half model using micrometers etc. Make a vertical grid that is ridgid and will stand away from the half model a couple of inches. Use a long needle to mark off the frame positions, buttocks, waterlines etc. etc. The vertical grid gives you the same information as taking all the measurements from the center line only in reverse.
The bigger the half model the more accurate the lines will be though you will probably end up doing some fairing.
It a lot less work if you can get the offsets somewhere.

[NormMessinger]

Which leads one to inquire, how accruate should one be when cutting molds for a boat, strip planked or lap strake. If one takes lines from a eighth size half model and scales up is one thing but to build a multi masted sailboat from a half model two feet long, say, it looks like give or take a foot is close enough.

[jwaldin]

You just need a barn full of fairing battens. When the stations are put in don't put them in say starting at the stern and then put them in one after the other. Start amidships with the first one then put in another halfway to the stern same with the bow. Use stiff battens and adjust as you go. You'll get a fair hull if you're careful. This will work for small boats.