Bow Shape development need help

[aussieav8r]

Hi Guys thought this would be the best place to start , I am an engineer who just got caught up in building his dad a boat out of plate alloy . I have built Fiberglass boats for years and have made some pretty nice craft , I am also a sheetmetal worker so I am not totally dumb BUT, I have drawn a design for a plate alloy fishing boat that looks great I have completed all the line drawings (old School ) on a board not a Cad program, my issue is how to work out the development for the Bow so that I can project the lines on a sheet of plate and cut it out then just wrap the sections up and weld them .

What I am looking for is how to develope the bow shape true length in flat pattern I already know that it should look like a segment of an orange peel so to speak but not wnating to wrap a 20 foot sheet around bulkheads then scribe a line around the keel due to the size , I would prefer to be able to project the lines onto the flat sheet first , I know it can be done easily on Cad but would like to keep it to the style I am used to can anyone help outhere

Thanks for looking Tommy

Originally Posted by aussieav8r

Hi Guys thought this would be the best place to start , I am an engineer who just got caught up in building his dad a boat out of plate alloy . I have built Fiberglass boats for years and have made some pretty nice craft , I am also a sheetmetal worker so I am not totally dumb BUT, I have drawn a design for a plate alloy fishing boat that looks great I have completed all the line drawings (old School ) on a board not a Cad program, my issue is how to work out the development for the Bow so that I can project the lines on a sheet of plate and cut it out then just wrap the sections up and weld them .

What I am looking for is how to develope the bow shape true length in flat pattern I already know that it should look like a segment of an orange peel so to speak but not wnating to wrap a 20 foot sheet around bulkheads then scribe a line around the keel due to the size , I would prefer to be able to project the lines onto the flat sheet first , I know it can be done easily on Cad but would like to keep it to the style I am used to can anyone help outhere

Thanks for looking Tommy

look at my gallery and then call me, not tonight!! 0754561210 or by msn lazeyjack@hotmail.com or lazeyjack on yahoo messenger

[Tad]

This may help, it was written by Chris Barry, who used to be around here quite a bit.

Working With Developable Surfaces.doc

[Earl Boebert]

The classic description (or so I was told) is by S.S. Rabl. PM me with your email if you'd like a copy.

Cheers,

Earl

tim here is the file, I dont have your address
rgds Stu

Originally Posted by Tad

This may help, it was written by Chris Barry, who used to be around here quite a bit.

Attachment 19084

That is VERY useful thanks Tad!!!
but tedious) the Dutch used a system with sticks, two long sticks for chine and sheer , and took and marked the true length upon them, they then used shorter sticks to criss cross them, the lengths and positions of which were lifted from the body plan
the guys were very secretive about the making of this pattern and quite selfishly would not share it even with apprentices!!

[Wayne Grabow]

"the Dutch used a system with sticks, two long sticks for chine and sheer , and took and marked the true length upon them, they then used shorter sticks to criss cross them, the lengths and positions of which were lifted from the body plan
the guys were very secretive about the making of this pattern and quite selfishly would not share it even with apprentices!!"

I have seen this described elsewhere, and the description was quite clear. It didn't appear to be difficult to master. Now if I can just remember where I read it.

[aussieav8r]

Thanks for heads up ideas , I found in one of my old sheetmetal development books a formula that gives a very close example to what is needed, it explains how to develop a spout on a early 1900's bath tub , its just the spout development and guess what it looks just like the bow of a boat , I have used the formula to project the dimensions and true lengths and shall make a 1/4 scale model of the bow out of some sheetmetal tommorrow I will set it up on some frames and see how close it develops around the sheet, I shall stay intouch with my progress , The book by the way is advanced sheetmetal development from 1943, and no I am not that old it was a hand me down from one tradesman to another and so on until this apprentice was allowed to have it , I have copied the pages relevent and will post the up if they work .

Regards Tommy

[Earl Boebert]

A long discussion of this topic appears at:

http://www.woodenboatvb.com/vbulleti...ad.php?t=14513

Also, I've attached the Rabl paper, which appeared in Kaiser Aluminum publication. The PDF is made from 600 dpi scans so you can enlarge it in Acrobat reader to get the details of the diagrams.

Cheers,

Earl