Boat extension

By changing the ratio beam / length will also have to check the ship's stability.
As I said earlier, perhaps change the trim of the ship, perhaps change the draft and, therefore, the depth at which the propeller works, perhaps, if you do not change the frame spacing, no need to change the scantlings. Anyway, we should check some small things.

 

You're right, we've not been stretching designs by 12% and more at all and certainly not since the advent of CAD. We're the fools that blindly built design catastrophe after catastrophe, just in hopes some 3D modeler, could someday bail our helpless souls out, of our self generated despair.

How may yachts have you personally built TANSL? I have dozens (several) under my belt, including many of my own design. I've stretched designs, I've shrunk them and it would seem all this time, I've just been in need of someone like you. Damn, what fools we must have been to think we could go to the moon, using just a slide rule and a pencil. What an audacious bunch we must have been. It's a good thing you modelers came along and saved us. Hell, the Wright brothers must have just been shear lunatics, instead of the reasonable and methodical individuals they actually were.

I haven't suggested developed panels could be stretched, in fact I previously mentioned they'd have to be lined off, which is a standard process, though one I'm sure you've never performed. Any change to the hull form or structure, would need a new line off, which in most cases would be performed either on the lofting or more usually, after the station molds have been erected on their new centers. I wouldn't imagine you've spiled off a panel or plank either, unless of course you nursed yourself through the process, with a CAD generated template.

CAD is a wonderful tool and I use it daily, but it's not a necessary tool, when you have plans in hand. It's quite simply reinventing something that already exists, in this case. To learn virtual modeling, just for one boat is an absurdity, by any stretch of the imagination, as it serves no useful purpose, other to reinforce what the plans already show. The OP is not going into production, nor anticipates a lot of significant changes, so why would he spend months learning about virtual modeling, when all he has to do is spread out the plans and get started? He wouldn't even need a 3D model if he was getting the station molds or frames CNC cut. Every single CNC firm I know, can easily work from his plans or a BMP or JPG of his plans, to create a cut file, so where is the need for a solo builder, making a single craft, needing to learn something (modeling) that will take many months to get proficient at? How long did it take you to acquire good 3D modeling skills? Where you trained and if so, should this poster now consider going to school for it? How much more unnecessary stuff do you suggest this poster put himself through, before moving onto the actual build? Maybe a metallurgy course or a WestLawn course? How about a few months under the wing of a master carpenter or better yet maybe a quick tutelage with an electrician, plumber, pipe fitter, rigger and finisher, just to be surer he's fully versed? Maybe in another decade he'll be ready . . .

 

PAR, will not waste my time to answer you.
If someone wants to refute your opinions and downs, I'd appreciate it. Seem more objective than if I do it.
Just want to point out one thing. The many ships that you have built not let you guess what my knowledge and my experience. Let imitating thy way, I also do a seer: I am and I have always been able to work without a person like you by my side. You, on occasion, need to work with a NA to you.
Cheers

 

Obviously a translation issue going on there. So, how many yachts have you built?

 

I had thought not answer but as I appreciate you, I do not want you to feel frustrated.
Yachts?, none. I guess just like you.
Other boats?, none. I guess just like you.
Now, being part of a team that built boats, many times.
Direct and final responsable of building a boat?, do not remember well, but let's say as little 230 times.
I hope I have satisfied your curiosity.
Cheers.

P. S. I forgot. I built six wooden models of about 1 m in length, of different boats: three old, one supply vessel for oil rig, a fishing boat typical of the Bay of Biscay and a copy of the first steel ship was built at the shipyard "Spanish Company Shipbuilding "(Euskalduna) in Bilbao, Spain. I mean that, before making computer models, I've made ​​several of Wood.

 

Me considering the Potluck was true but as you continue reading the thread,
you will see that I've changed my decision and am now prepping to buy plans
for the Johns Bay boat 32

You are correct that I have started this thread to ask the pros and cons of
stretching the boat to 36 ft but not the pros and cons for keeping the boat in
the original length.

I value everyone's opinion and even though it's a bit hard for me to read, I am
understanding it little by little.
What I do understand is that when extending, it is about the way you want
to do it.
Do you want to go deep into detail and try and fix the imperfections when
extending or do you want a longer boat where imperfections don't matter that
much.

For me it doesn't matter as much as having more space does.
Having more space it the real reason that I'm considering extension.

With this post, it is not my intention for more people to start arguing.
I am thankful that both PAR and TANSL have answered my question.

 

My experience was that our pelin 29 ft by 10ft was a miniature of the next model 36 by 12 which friends built. At all cost go for the bigger boat eg.johns bay 39 if you feel the 32 is too small. You only get one chance at this
you will never regret that decision Eg. In a 32 the dinette is always too small, toilet is too small In a 39 you can do the 4 bunks forward with comfort. Maybe this design is easy to covert to strip plank and glass rather than plank on frames. It would be great if a firm could cnc rout frame templates Im sure Tad has the ability to work this out

 

Understood, hope the plans won't be too pricey though.
Having CNC templates would be great if only the shipping wasn't so expensive.
I don't live in the US, I live in Curacao and island off the coast of Venezuela.

 

Albert, if you provide me your boat plans, I would have no objection to make templates for CNC. That will provide me entertainment, so do not worry about the price.

 

Sounds like a plan, thanks

 

its not the plan price that makes a difference between 32 and 39. 39 will be more expensive - by a fair amount too.

 

The difference in size between the 32 and the 39 can be seen in the volume of the two, which is substantial. This is what you're building, so the 39 would be likely twice as costly, because it's nearly twice the volume. A stretch of the 32 would reduce this ratio considerably, making it a much less costly build.

 

Albert was saying the 32 is to small and wants to extend it. Maybe is better to head for a 39. A 40 ft boat is generally twice the volume of a 30ft but generally only contains 50% more material. 40ft is a good size because the expensive part of fitting out things can be a standard house size Eg galley showers doors etc Engine is much the same just turbo +$2000 Getting every thing you need in a 30ft boat is hard work .Remember he is in a low wage country. So labour may not be an issue. A lot of boats up to 20metres are using 50mm ply cnc ring frames with stringers and ply or strip planked So going from 30 to 40 ft wouldn't be much greater cost and just put what you put in a 30 ft boat into 40 Few photo of a 30 ft pelin and a 40 ft to compare http://www.boatdesign.net/forums/at...ttachmentid=86031&stc=1&d=1383468695383468649

 

I lean more to the nzboy approach. By moving from a 32 to a 39 or 40 ft, the price of the hull is not doubled and the price of another great chapter (main engine, equipment, services, electronics, plumbing, etc.) will be slightly higher but can never be twice. The technical chapter (Project, plans, building management) will be very similar in both cases.
In any case, it is necessary to study with rigorous technical and economic approaches going from one size to another.

 

Both of you should have a look at these two designs and make reassessments of the positions you've assumed. Boat building coats are directly related to the dent you put in the water. Do some simple calculations and see how much bigger the 39 dent is compared to the 32.