Scaling Plans

[DCockey]

Originally Posted by sean27

I am going to be building a Bateau HMD19 http://www.bateau.com/studyplans/HMD...htm?prod=HMD19
I am thinking about scaling the plan up a little. ......

Originally Posted by sean27

.... My main issue is that I need to learn how to draw out all the panels with the new dimensions in order to do a nesting plan. I will give free ship a try.

You might want to do some studying and learn how to layout a part from dimensions before trying to build a boat. It's a basic skill.

[sean27]

Chuck,

THANK YOU!

I will do just that. Draw it out on paper, cut out, layout on plywood drawn at same scale.

Originally Posted by Chuck Losness

You really don't need to use software to figure out the nesting on 4x8 sheets of plywood and it will probably be a time consuming adventure. As other posters have said just scale all your dimensions to the new size on a piece of paper for each part. Cut out each part and then start arranging them on 4x8 sheets drawn to the same scale.
When I made my dinghy, I expanded the length by 10%. I drew out the new panel shapes which was simple to do, cut out each piece and then arranged them on the 4x8 sheets drawn to the same scale. It only took an hour or two and I had it all figured out. Your boat being larger with more pieces will take longer but you should still be able to do it in one afternoon or a couple of evenings at the most.
I think that you are over thinking this. Computers aren't always the easiest way to do things. Learning the program will take longer than just doing on with it pencil and paper.
Just my humble opinion. Good luck with your project.
Chuck

[sean27]

Originally Posted by DCockey

You might want to do some studying and learn how to layout a part from dimensions before trying to build a boat. It's a basic skill.

I know how to lay out the parts on paper/plywood, but was caught up in the thought that I had to draw out the new scaled up plan in some kind of cad/computer program. I am going to take Chuck's advice and draw it all up on paper with the new dimensions at 1/10 scale and do the nesting plan manually.

[DCockey]

Originally Posted by sean27

I know how to lay out the parts on paper/plywood, but was caught up in the thought that I had to draw out the new scaled up plan in some kind of cad/computer program. I am going to take Chuck's advice and draw it all up on paper with the new dimensions at 1/10 scale and do the nesting plan manually.

Good to hear. It's understandable that you might think it should be done on a computer give some of the discussion here with folks who seem to believe that software is the key element for boat design.

Some designers such as Phil Bolger work hard when designing a plywood boat to maximize the use of each sheet of plywood. If that's true for the design you are interested in then you will probably find the amount of plywood needed after enlarging goes up more than expected.

After you get the parts laid out consider building a simple model using cardboard. It will help in learning how the boat goes together.

[philSweet]

Sean, very briefly, can you tell us why you want to enlarge this design? Do you want to fit in an additional feature, or do you feel the boat as designed is built for munchkins and you need more elbow room. Maybe you just have a bigger trailer at your disposal. The way boats scale, one would not ordinarily just apply a fixed factor to everything. Seats, bunks, headroom might best be left alone. You must be careful how the joinery work comes together in this case. Stretching only the length is usually the easiest thing to do because most designs have already pushed the panel width to the max. However, it is not simply a matter of stretching the panel flats since the angles all change. I'm guessing that's what you meant by saying a bulk scaling factor was all you knew how to accomplish. Please be conscious of preserving the original design's grain orientation and good face up orientations when creating the new nesting. You can't just nest them any old way. Also check the mechanicals. Will the motor mount still serve or was it at its limit geometrically, you may require a longer shaft. Will the standard control cables still work or do you now need an extended set. You'll have to think about how the glass sheath goes on as well regards the overlaps and reinforcements.

[michael pierzga]

Sounds like sensible advice. That boat looks a good candidate for stretching.

Also by simply stretching the boat 8 percent , you can preserve much of the original ply nesting.

As was noted grain orientation is worth considering when you re nest. Some components care little, some need grain respected.

[DCockey]

Be aware that if the design is stretched in length only, the shapes of the panels will fundamentally change, not simply stretch in one direction. The expansion of the surfaces to obtain the shapes must then be redone. This is a task which good software can greatly simplify.

[michael pierzga]

Sure, But stretching the hull panels is straightforward. That's a 4 panel boat plus a transom.
I would have no idea how to go about stretching all the interior, cabin components.

Its these components that the original design nesting plan is most useful for.

[DCockey]

Stretching the hull panels is not straightforward if the design is stretched in only one or two directions (unless the design is a scow with parallel sides). The distances along the hull do not scale with the the length because the hull is curved.

[michael pierzga]

Ya, sure... but youre talking about drawing, lofting on a computer. I dont have any computer skils.
I would simply set the frame or frames at B max plus transom on the jig , play around with a long batten batten until I got the stretch propotions correct, then measure for the ply panels. Its how I added to the last skiff. For me Its the easiest way.

I guess is a good intellectual challenge to master the computer, but Id have to spend weeks just learning how to use the software and even then my eye just cant "see" on a computer.

[michael pierzga]

I guess the big question is why stretch the design to begin with ? On my skiff I needed just a bit more buoyancy aft to float the new, heavy 4 stroke outboard and keep the skiff on her lines.

[sean27]

After thinking about it, I am not going to scale the design. The boat is large enough for what I need it for and all the potential risks that go along with scaling a plan will be eliminated.

I have started a model.

[philSweet]

Excellent. you will soon notice that the panels will not lay exactly flat against a dead straight frame edge. The frames should have a small bow to the faces. In this design I think it will be quite small, but the frames should be eased to accommodate the shape of the panels. On the real boat don't draw the panel flat against the frame if it doesn't lay that way, you will create and ugly hump somewhere. There is a paper attached which explains a graphical way to develop the amount of bow on the frame. Or you can just adjust during the build. The plans should explain how they want you to deal with this. Hopefully, they have given you the curved shape on the plans.