For Creative and Quantitative People

Put the paper between 2 acrylic sheets to minimize distortion from bending. Make sure paper is on a parallel plane with bulkhead stock and do check proportions from time to time to expose and eliminate distortion.

 

Or you could use a pantograph.

Here is how to make one.
http://users.hubwest.com/hubert/mrscience/pantograph.html

 

DC rite it has to be exact, better still use a big pantograph. that why mylar is used, shrinks a lot less than paper also watch humidity and temp
Any print shop however will point you to a mylar big size printshop wich may not be the most creative way but probably the wisest way to go
if you want to saw yourself, also plan the nesting, you may print bulkheads over eachother using one print. From between the sheets on my phone.

 

Try projecting a grid patern and verify if the resulting lines are straight, square and evenly spaced. I suspect this projecting idea will work poorly.

 

I have used a projected image for artistic purposes (in that case lettering on a stage floor). I was very happy with the results, but accuracy was not in any way critical, as long as the letters were readable. The technique was exactly what you suggest here, so it does work.

However, I would suggest that you set a datum (could be the corner of your material) then plot your offsets and join the dots. This will not be the time-consuming part of your build.

Tim B.

 

I´ve helped my eldest doughter making a wall painting with similar methods.

This is how I would do it:
Scan the images into the PC.
Use a projector connected to the PC for projecting images on the wall.
Create a reference grid pattern in the PC and use it to check distortion.
There will be distortion, but to some extent it will be possible to reduce the distortion by changing the projection angle by moving the projector (or the wall which could be more difficult). If the remaining distortion isn´t acceptable you will have to find (or write) software to correct the distortion by anti-distorting the image before projecting it. I haven´t checked, but if I manufactured projectors or cameras I would include such correction software in the projector or in a separate software suite. Maybe Photoshop or some other similar software has this function.

If you can work with a small field of view and large distance to the wall you will get the least distortion.

Erik

 

Thank you for all the advice, everyone. I figured someone would have some exposure to this type of method and it would appear some do.

I guess this might not be the best way to go in order to save time, given everything that has been said on the thread.

Thanks for the input. It was an idea worth exploring, but there are probably faster ways, since I'd have a lot of work to do in making sure the projections were dimensionally accurate.

 

Bntii: I'm going to use some battens and a hot glue gun to make up quick templates.

I made some changes to the shape of my hull, so the bulkhead patterns aren't 100% accurate anyway. Thank you for the offer. I think I'll do it by making the template instead.

 

Well us old backyard boatbuilders simply used a piece of soft copper pipe (3/8 fuel line) and pressed it against the bulkhead line on the hull forming the shape of the hull between two reference points. We then marked this out on a 1/8 sheet of pattern making door skin ply. Continued the process from the last reference point to a new one until half the hull bulkhead was marked out. We then cut it out and fit it in place and fine tuned the pattern by planing or knife cutting off any high points until the pattern fit as tight as possible against the hull. Then we worked our way around the pattern again making notes say every 6 in or so, plus 1/8 here, minus 1/8 there and so on. Once that was completed use the same process to make the remaining half pattern but make it 1 or 2 in. horizontally wider than needed. That way when you fit the two patterns in place they lap, simply mark a line down the lap and you will end up with a perfect fit between the two halves. Sounds like alot of work but you'd be amazed how fast and how accurate you can cut a bulkhead from such pattern making. I would say on a 30 ft. hull bulkhead i can make an accurate pattern 1/8in. tolerence in 1 to 2 hr. These days I use Kyteck 1/2 in. plastic/alum/plastic sandwich house plumbing pipe. ---Geo.

 

That makes a lot of sense, you've gotta mark in the bulkhead landings square off hull C/L & W/L any way & the terms "check on ship" & "as built" come to mind. Templates are quick & easy esp if you "spile off" the perimeter using a steel rule or "spiletto".
Regards from Jeff.

 

Yep... the template thing is the way to go, I think. Thanks for the help, guys.

I'll probably start on that this weekend or early next week. Still have to figure out how to put in the stem and get it looking perfect. I'm doing those "razor blade" bows like on Gunboats.

 

What you need is an opaque projector not an over-head projector as pictured above.

-Tom

 

http://en.wikipedia.org/wiki/Opaque_projector

Good idea but be careful and don't leave it on one spot for long.:
"Because they must project the reflected light, opaque projectors require brighter bulbs and larger lenses than overhead projectors. Care must be taken that the materials are not damaged by the heat generated by the light source."

You might be able to get by doing the tracings at night with a dimmer bulb that puts out less heat.

 

Sounds good cat.
I am away from the shop flat on my back with the plague.. but stand ready to plot out some templates if it would help.
If the files are stackable I can do up a bunch of outlines on one template and you just punch through with an awl to get each one marked down.

If doing direct take offs with battens- mind that the hull is not bent out of shape when you do it.
Also- there is a "tick stick"/jogging stick method for taking off hull shape which is faster than battens and hot glue. I have a good description in one of my books and will post the page if I can find it.

http://www.boatdesign.net/forums/fi...at-building/scribing-awkward-shapes-6143.html


http://books.google.com/books?id=W3...=onepage&q="tick stick" hull template&f=false

I use a far narrower piece of ply stock for the tick record than shown in the above.

 

Sorry to hear you are sick, bntii.
Did your wife hang the monitor over your head to make blogging easier for you?