Molds - from paper to wood, from theory to practice

[Bear_Ludo]

The subject has already been discussed many times but I think a new post could be the occasion to collect or give updated information on the subject. So your comments and advices are welcome
Initially I was answering to this post:http://www.bearmountainboats.com/phpbb2 ... php?t=2204

For making the molds two things worries me:
- How to draw the molds on the paper accurately to the calculated design
- How to accurately transfer these lines to the mold material

Here are my toughts at the moment:

About the first point, all hand operations in the batten technic can potentially lead to some mistakes. The ease of use and the power of CAD programs seems more attractive both for good accuracy and potentially less mistakes. After some trials, using a CAD program is not as straightforward as I tought, the mathematics having their own rules and limits. But there are interesting technics that are worth investigating. (in the same other post above)
The boat industry is using such programs so with some training I should be able to output more or less good results.
Nevertheless, I am also convinced that buying the plans is a great advantage if not necessary. First I will be sure to build a boat in repsect to the original design (that one I choose) but it is also the only way to compare, verify and improve the CAD or batten technic.
On the other hand, some says that 1/16" accuracy is enough (it sounds huge for me !!). Added to this, strips naturally fairs the hull and I understood that when the hull is removed off the molds it takes a natural form that is probably a bite off the original design.
So accuracy is important but maybe not as I imagine it. I am sure I would not be able to find differences in paddling Canoes with such little differences. The difficulty is to find the good balance point between accuracy (and the effort it needs) and the final goal which is to have good paddling moments.
This is not easy and in the doubt I balance more on the accuracy side

The second point, that sounds tricky for me is transfering these carefully drawn molds curves to the molds material. For the moment, I am in the way to make mold templates in MDF and then use the templates to route the final mold material with a copy bit. As the Prospector is a symmetrical design, I will only need to fine tune each different mold once.
Now about the transfer itself, what I have in mind is to plot (full mold) in a specific shop on a thick paper, then cut along the curves and use a pencil to mark the MDF. The reason for thick paper is to provide a good and rigid guide to the pencil.
I remember I've seen once on the Web someone transfering prints (on usual paper) on a material (don't remember which) using a domestic Iron. I can't find it again and after some trials that failed I gave up.
Has someone alerady tried this ???

Yours comments and advices are welcome

Ludovic

[RonMc1954]

I can comment on transfering from paper to mold. All I did was to cut the paper about an inch larger than the pattern and used a spray adhesive to glue the paper on to the mold material then cut with a jig saw. I just left the paper on the cut-out mold and all center lines and other marks are already there. This was what was suggested in the plans I purchased.
Ronmc1954

[canoeblderinmt]

Ludovic,
I built my first two canoes by lofting from a book. I used poster board, which is thicker than regular paper. I plotted the points after drawing a 2" x 2" grid on the poster board. I just smoothed the lines with a batten and by hand so that they looked good to my eye. Then I transferred the lines to the plywood. I cut wide of the line, and used my 10" disk sander to fair things up. I screwed opposite stations together for the sanding to ensure their conformity. Then mount them, true them up and start stripping!

Bonne Chance,

Greg

[Bryan Hansel]

I've hand lofted the forms for several boats and the panels for a kayak. The boats turned out great. To transfer the lines to the wood, I used carbon paper and traced the lines that I drew.

[Glen Smith]

I would use one of the methods proposed by Ron, Greg or Bryan. CAD programs don't fair the lines in the same way you can with pencil and batten. The more steps you introduce into the process to get from offsets to usable molds, the more risk there is of an error slipping in.

[Fred G]

Amen - I used the posterboard method. Worked great

[Bear_Ludo]

Thanks all for you comments and advices !

Greg, what method do you use to transfer the lines onto the mold material ??

Brian, when transfering with carbon paper, do you do it by free hand or use also a batten ??

Glen, I agree with you, the more process the more potential mistakes. Being new to this, I really balance between the CAD and Batten technics. I will probably do both to experience it ;o)

Ludovic

[Bryan Hansel]

I use a batten on one side and usually freehand it on the other after I have a nice solid line drawn.

One thing that I do is to use a piece of carbon paper facing down and one facing up. The one the faces up copies the line to the backside of the pattern, so when I flip it over the centerline, I have a matching pattern that I can freehand onto the plywood.

[canoeblderinmt]

Ludovic,
I drew all the stations (molds) onto one piece of poster board, with each station on top of the others. I then cut to the outermost line (station 6 in my case) and used this as a template to draw the outline onto the plywood. I made vertical and horizontal reference lines so I could "Flip" the half form and make a complete station. Then I cut to the next station and repeated the process. I used a minimum of poster board that way. I spent a little time on the stations after I cut them out, ensuring that they were smooth and true. Worked good for me.

Greg

[woodman]

i simply photocopied the plans eight times and gluedd each copy onto 6mm MDF. Using a jigsaw and a hand file i was able to construct an accurate template for half of each mold and the stems.

Next step is to use my router to copy these into 12mm particle board.

[paul]

As usual everyone has something that works better for them based on unique circumstances.

For me it was the method described in Canoecraft.

I originally tired copying to poster paper and then tracing to MDF. Unfortunately there was slight deviation from free handing and more deviation from cutting with scissors. This led to minor discrepancies when transferred to the MDF. So after much work tracing and cutting and re tracing to the panel i scrapped that method.

I then went to photocopies. I went to the local copy shop and used their blueprint copier which ran the original blueprint thru a set of roller and created me another copy the same size as the plan i ordered. When i got home there was a little under a 1/16" of a difference in the height of the copy. (i could not accurately measure the other dimensions).

So i was left simply with the original option of tracing directly from the plans to the MDF using carbon paper.

In the future i will hone the technique of using a batten to improve on my freehand.

Paul