Building a scale model

[dalan1]

Has anyone out there built a scale model of plywood lapstrake hull design? I'd like to model a design of mine (a 14' glued plywood lapstrake sailing dinghy) in 1:6 scale, a size that ought to be big enough to be accurate and would facilitate using the structural design of the actual boat. I won't bother with a laminated stem for the model, but I would like to actually lapstrake the hull.

My questions regard the planking for the model. What to use? Lee Valley has micro-thin birch plywood (0.8 and 1.5mm) that I think would work nicely, but I'm unsure which thickness would work best. The 0.8mm would obviously take the bends better and would be closer to true scale (actual boat will use 6mm ply).

However, unless I can find a supplier that offers this thin plywood in larger sheets (Lee Valley's is only 25" x 25"), I'll have to scarf it. Is it even possible to scarf plywood this thin? What about beveling the lands and cutting the gains? I would think that the thicker material would be easier to work with in those respects.

Any thoughts?

[Chadd Hamilton]

Well a 1:6 scale would put the model at just under 2 1/2 feet I think. I used a tablesaw to resaw some 1"x3" eastern white cedar planks down to a little less than 1/8" in thickness, then cleaned up the rough face with a micro plane. This takes a little time to do, but if your rip fence is good and your blade is square you'll have no problems. Of course, this is assuming that you have access to table or band saw.

Another approach is to use balsa sheets from the local RC hobby shop.

[DerekW]

Check with your local sheet-goods supplier. At least one plywood supplier here in Canada will get 8 x 4s of that super thin birch ply on special order...

cheers
Derek

[Bruce Hooke]

Aircraft Spruce and Specialty Co. has 0.4mm, 0.8mm, and 1.5 mm Finish birch plywood in 24" x 48" and 48" x 48" sheets. Only the 24" x 48" sheets can be shipped by UPS.

I would feel comfortable scarfing plywood that is this thin, and cutting things like gains, but I think to some degree this has to do with mentality -- when I was a kid I was into model trains and I remember building a HO scale (1:87 IIRC) model tool shed complete with a 3/16" long hammer and other tools. So, the issue is not so much, will the wood handle this sort of miniature work (it will), the issue is are you up for it, and do you have tools that are up to it? It doesn't take much in the way of tools: a miniature plane, a good model making saw, and some exacto knives would probably be the main tools...

If you have doubts about working at this scale I would be inclined to scale up the whole model rather than just the planks. A 1:4 scale model would be 42" long and would call for 1.5 mm planking.

[Bob Cleek]

Many modelmakers use a drum thickness sander to turn out thin plank stock. As said, resawing thin slices is also an option. For smaller scale work, card stock from the art supply store is used and then painted. I have had good success using veneer stock, which can be purchased from any good woodworking or specialty lumber outfit. This comes in sheets of various sizes. I've used stuff that comes cut at about 8" x 24" and it isn't particularly expensive. You can get all sorts of woods. Walnut worked well for me.

[Bruce Hooke]

I just noticed that you are in Massachusetts. I'm not sure where in the state you are located but Boulter Plywood in Somerville (Boston area) has plywood down to 1/64 (0.4 mm) in full 4x8 sheets as well as various smaller sizes down to 2x4 and 1x8.

[dalan1]

Chadd: I do have a good tablesaw & fence, and I have used it to resaw thicker stock to get thin panels, but it gives me the heebiejeebies every time I do it and I can't imagine trying to resaw a slice as thin as 1/16". I don't have a bandsaw, unfortunately (I know, I know, it's illegal to try build a boat without at least a 20" bandsaw! ).

Bruce: thanks for the ref. - I'll check them out. I'm not uncomfortable working at the scale of a 1:6 model and I've got the tools except for a miniture plane - good suggestion.

An even bigger scale would of course be better, but my rationale for going with 1:6 is mostly for convenience - it's the largest scale at which I can output full-section patterns directly from my CAD program using legal-sized paper on my laser printer. 1:6 is also the perfect scale for using Barbie and GI Joe for ergonomic design studies for cockpit layout.

Speaking of Barbie and GI Joe:

Little Sally is telling Santa what she wants for Christmas. "I want Barbie and GI Joe". Santa says, "but Sally, Barbie comes with Ken", to which, Sally responds, "No Santa, Barbie comes with GI Joe. She fakes it with Ken."

{rimshot}

Now that I think about it though, I probably could get half-hull station patterns on 8 1/2 by 11... I might be able to do 1/4" scale after all.

I'll still have to figure out how to get full-sized station and stem patterns, when the time comes. I don't want to reloft it full-size, having already lofted it in the computer.

[dalan1]

Boulter! Of course. It didn't occur to me that they have super-thin ply. I've always thought of them for the bigger stuff.

[John Blazy]

Sounds like you'll be doing too much work (material choice-wise). Building the boat will be plenty enough, so do the model in the lowest cost, fastest way possible - not necessarily my method, but glean best application.
I made a 3/32 scale model of my design of a 14' stitch & glue plywood boat out of two pieces of standard poster board that I glued face to face with polyurethane glue rolled out. This created a stiff enough board/paper to bend my gentle radii and yet transfer the hull patterns - full length - directly to a template sheet to trace around, then scale up from that to full scale.

The upper left shows the 3/32" scale pattern sheet with the patterns taken from the model's actual hull sides/tops/transoms/bulkheads etc. Above that, I am holding a clear "scale grid" I made out of thin plastic sheet that I scored grid lines to 3/32" from my architects scale at 2" x 4" rectangles. The full scale templates were made (lower right) on thin Lexan diffuser film (cuz I had a ton of it) but could have been done on thin paper or vellum. The film is placed over a full scale grid marked with a 'sharpie' pen every 2" (vertical) x every 4" (horiz) over 15 feet by about 3 ft. The reason I made the grid once on the layout table, is so that I could simply lay the film down over the grid - seeing the lines through the film, mark the intersections from the corresponding scale (clear grid taped over the pattern) and fairing the lines uniform with a long, bent batten. I used the same grid for each hull part.

They transferred to the plywood, cut, and after a few on-the-fly changes like lengthening the stern, the plywood stitched together perfectly with only a little carving. This was four months ago and now I am almost halfway done with the boat.
Glean what you can like use the posterboard idea, and for a larger model, just glue up more layers staggering the joints when lengthening. It'll cut well with a razor knife and hot-melt glue will be fun. - JB

[dalan1]

John: Nice model. I also like the simplicity of just scaling up to full size station molds using a grid. I'm thinking I can probably just record the locations of the plank lands on each of the stations, transfer them directly to MDF station mold stock, and connect the plank land spots with straight lines. It seems to me that "faceted" molds would make sense for plywood lapstrake anyway, right?

I guess I'm just a bit nervous about this being my own design, and while it looks good on the monitor, I'm not yet convinced that it'll go together in wood. Perhaps it is overkill for a model, though. I'll have to give it some thought.

[ahp]

Charette, the artist,architect and drafting supplier has thin sheets of various wood down to 1/64 thick, but they may only be 30 inches long. You need to check

[Ian McColgin]

Veneer stock, modlers balsa - most anything will work. I made the model of Leeward at 1-1/2" = 1' because then 1/8" on the model was 1" for the real - very convenient.

That size towes well if you want to 'tank test' in the nearest puddle and while you'd have to recalculate for yourself, I remember that at that scale pennies made a convenient modeling of some round number of ballast.

[Bruce Hooke]

The skiff I am building now from 1/4" plywood is also my own design and I found it very reassuring to do up a half model in plywood that was the correct scale thickness relative to the full size boat. It gave me a reasonably good assurance that the plywood would bend into place on the real boat. So, I can certainly relate to why you want to do roughly the same thing.

You probably know this, but just in case, I will warn you that in my experience with both laser printers and inkjets, the dimensions that go across the paper tend to come up pretty much to scale, but the lengthwise direction is often somewhat off because it is dependant on how well the rollers in the printer do at advancing the paper at exactly the right speed. So, be prepared for this error.

BTW - I have an inkjet printer that will print on 11x17 paper so if you have a few sheets that you need to have printed at that size I'd be happy to run them off and mail them to you. I also have autoCAD light so I can open most CAD drawings, but if you have the ability to create a PDF of what you want that works even better...

[ion barnes]

I have a 15' drift dory model in progress in a scale of 1.5" to 1' and used 1/32 birch ply because it has more resillience that the card stock which was my first choice. Got my plywood at a Michaels craftstore, 12" x 24". Ion

[JimD]

Originally posted by dalan1:
Chadd: ...I can't imagine trying to resaw a slice as thin as 1/16".

dalan1, I only have a cheap-o table saw and I cut strips about 1/16" without any trouble for the models I build.
jimd

[Pekka Huhta]

I have planked three small lapstrake boats with about 1/20 in (about one millimeter) thick pine planking. I just sawed about 1/16 strips and planed them with a miniature hand plane thinner. On the ends the thickness reduces to virtually zero.

I have also built a model for a stitch and glue dinghy that's made of 0,8 mm plywood. That was built from a kit and the hull took some 10 hours to finish. Easy job, too easy. There has to be some challenge in these things. Gluing things up is easy, just imagine riveting a 10" long boat with actual copper rivets. That's fun [img]smile.gif[/img]

More of my modelling work is at http://www.puuvene.net/phuhta/pram/pram.html . Unfortunatley I don't have the pictures of my latest and neatest boat, a traditional Finnish rowboat built after my fathers boat. It really improves your eye for boats building a scale model just by heart.

One of my own designs, still waiting to be built 1:1



Pekka

[Ed Neal]

I planked my model from clear Aspen stock Home Depot was selling. It resawed well and didn't split or crack in bending. It sanded smooth with very little or next to none grain detail.

Resawing on the table saw is a lot easier if you equip it with a table saw insert that leaves no gaps around the blade.