Hard chines from a drawing.

[edik]

I found a really neat design for a triple hard chine sailboat. The problem is - I don't know anything about the designer or how to get additional info. I then went ahead and built a model and it is as cute as they come and would make a solid cruiser. Well, when building a model, I simply used the available drawings and transferred them onto a larger grid to get to the desirable size. Can this be done for a real boat? The boat is 10.5m long and 3.3m wide. Copying the drawing on to a 1:1 size grid is not a problem, but will this work? Will this be accurate? Has somebody done something like this before? I was thinking of using Alu.

[gonzo]

The lines will scale up or down with no problem. However, it doesn't mean it will work. Hulls will not scale more than 15% or so without affecting handling badly. Also, you need to re-engineer the structure.

[edik]

Originally Posted by gonzo

The lines will scale up or down with no problem. However, it doesn't mean it will work. Hulls will not scale more than 15% or so without affecting handling badly. Also, you need to re-engineer the structure.

I'm not sure I understand the sentence in bold. Could you elaborate? Also, not so long ago, boats were built from wooden models that were then sliced up. I would think that that method was not very precise and, yet, some of the best looking boats were built during N. Hereshoff's times. And they sailed well. Can the lines be scanned into a computer and then corrected, if necessary, with a boat building software? Is there a software out there that can generate a table of offsets based on scanned lines?

[Nick.K]

Look in the free software section on the forum, free-ship and delft-ship are easy to learn and will let you play around with designs and even create the files for the shapes to cut to make the hull. For a real project you will need a naval architect or some serious study.

[DCockey]

Originally Posted by edik

I'm not sure I understand the sentence in bold. Could you elaborate? Also, not so long ago, boats were built from wooden models that were then sliced up. I would think that that method was not very precise and, yet, some of the best looking boats were built during N. Hereshoff's times. And they sailed well. Can the lines be scanned into a computer and then corrected, if necessary, with a boat building software? Is there a software out there that can generate a table of offsets based on scanned lines?

I think what Gonzo was referring to is if the size of the actual boat is changed by more than 15% from the intended size there are likely to be problems with the way the boat handles unless other changes are also made. Nothing to do with the scale of the model or drawing used to design the boat.

[Ad Hoc]

It is not possible to say for 100% how the handling will be affected without knowing the basis hull dimensions such as its displacement, LCG and VCG.

Since when you geosim hulls, you can elect to do the following:

1) keep the final proportions the same as the basis;
2) change the final proportions, but improves the handling;
3) change the final proportions but is detrimental to the handling.

Without knowing the basis hull form principal particulars, it is hard to say whether you’re in the #1, #2 or #3 when you finish.

If you do know the particulars of your basis hull and geosim the hull (scale) you may find that you cannot keep the final LCG and VCG and displacement in proportion, simply owing to the scale.

For example. If the basis hull is say 5m in length and has an LCG at a midships, yet when you scale yours up to 10.5m, and then locate all the items you want in the locations onboard you want and the final LCG is 20% aft of midships, you have a problem. So you’re in #3.

You can then elect to change your layout to balance the boat to be the same as the basis hull, ie LCG at midships. If after endless changes you cannot get the LCG the same, say best you get is 5% aft, you have to decide if this is good enough.

But without knowing the basis hulls performance at various LCGs, you wont know anyway.

But being 5% aft is significantly better than say 20% aft.

Same with the VCG.

So, gather as much data regarding the basis (original) hull as you can, and see when you geosim the hull how closely you can match the original particulars. This is also of course assuming the basis hull has excellent handling characteristics and those that appeal to you to begin with to make such a judgement call too.

[thudpucker]

I have to admit I don't know what Hard Chines are.

Do Rubber boats have Hard chines....

[edik]

Originally Posted by DCockey

I think what Gonzo was referring to is if the size of the actual boat is changed by more than 15% from the intended size there are likely to be problems with the way the boat handles unless other changes are also made. Nothing to do with the scale of the model or drawing used to design the boat.

I would keep the original size. I know the length, the width and the displacement of the boat. So I thought I would use a 1:1 ratio grid and transfer the lines from the drawing. Would this work?

[Milehog]

Originally Posted by thudpucker

Do Rubber boats have Hard chines....

Possibly when they are folded up.

[tunnels]

Originally Posted by edik

I found a really neat design for a triple hard chine sailboat. The problem is - I don't know anything about the designer or how to get additional info. I then went ahead and built a model and it is as cute as they come and would make a solid cruiser. Well, when building a model, I simply used the available drawings and transferred them onto a larger grid to get to the desirable size. Can this be done for a real boat? The boat is 10.5m long and 3.3m wide. Copying the drawing on to a 1:1 size grid is not a problem, but will this work? Will this be accurate? Has somebody done something like this before? I was thinking of using Alu.

If you can bulid from sheet alu or plywood you can build same in glass as well . !!
Totally glass foam glass and ring frame with layers of uni running round the inside of the ring . Use the eye beam concept !. could make the whole boat from glass deck included !!.

[tunnels]

Originally Posted by thudpucker

I have to admit I don't know what Hard Chines are.

Do Rubber boats have Hard chines....

If you dont know what hard chines are then you need to go find some books to read about boats and boating !! or go find a warm sunny place some where and take up Knitting !!
Boats are floaty things what sit in water ! they come in all imagionable sizes and shapes and every colour of the rainbow !

[ancient kayaker]

Originally Posted by thudpucker

I have to admit I don't know what Hard Chines are.

Do Rubber boats have Hard chines....

ha Ha. that one just creased me!

[tunnels]

Originally Posted by ancient kayaker

ha Ha. that one just creased me!

Soft chines !! or round bilged !

[gonzo]

Hard chine boats are really easy to draw. Getting the lines full size is what is called lofting. That gives you all the parts of the boat in actual size.

[thudpucker]

I was pretty sure I knew the Chine is where the side stops being a Side, and the Bottom becomes a Bottom connected to the Chine.
A five Sided boat has several chine's.
Hard Chine is a sharp turn from Vertical to semi-horizontal....and so on.
The Definition is so nebulous we could discuss forever and still sombody'd have questions.
A round tube Rubber boat wont hurt your Shins when you crash into the Chine