full-size paper plans

[Dalan]

A couple threads in recent days have touched on the subject of the unreliability of full-size paper patterns that derive from the moisture-induced expansion and contraction of the media.

As I await the arrival of my Gannet plans from Mr. Oughtred, I'm wondering just how bad of a headache I might expect from this - his plans include full-size patterns for the stem, transom, and station molds. The plans are already lined-off - how reliable are the plank-land marks on paper patterns?

Now I've also visited the websites of lots of folks who have built or are in the midst of building Iain's boats - somebody here is building a Fulmar in a garage that looks like a hospital operating room - and I haven't yet heard any first-hand griping about innaccurate patterns.

So what gives? Are full-size paper patterns bane or boon?

If you're out there, Mr. I'm-building-a-boat-in-a-level-4-clean-room, I'd love to hear your opinion on this! Oh, and a fresh link to your site so I can bookmark it this time and oggle your work some more while I wait for my plans to arrive.

[Chadd Hamilton]

Dalan, I've only built two boats from Iain's plans, but in those two projects, I didn't-nor should you, encounter any problems with the full sized mold patterns that he provides. As others in this forums who have built Oughtred boats can tell you, Iain's plans are very good.

Best of luck.

[SailBoatDude]

Like wood, paper has a grain and it shrinks and stretches across it with moisture content. Anything printed on paper will have some distortion as a result of this. There are materials, like Mylar and acetate that will have much less difficulty in this regard.

Run an image through a photocopier or printer with the page printing long ways then the same image again with the image printing across the short side. Cut them in half, through the image and line them up on top of each other and you'll see that one has "moved" a bit. Now imagine this across the widest station mold you have. The small amount off movement seen in the 8 1/2" x 11" test sheet will be quite large across a good size sheet used in the station molds.

Thousands of boats have been built, with great success, using paper patterns. No boat has been built with perfectly shaped hull forms. Measure from the baseline to the sheer on each side of any boat under construction and you'll find differences between the two. There is about a 1/4" difference between the sheers port and starboard, on my 48' project and I conceder this very good indeed. The 1/100 knot difference in freeboard resistance I'll have as a result, isn't to be concerened about.

[NormMessinger]

Three Oughtred boats here, made from Kinko working copies of the plans. It'll take a person with one hell of a lot better eye than yours and mine to see if anything is not fair and a tape more accurate than my Stanley to tell if they are not to size.

Which is to say don't worry about it.

[Bob Perkins]

There was discussion about this based on some stuff I brought up a few weeks ago - I had already made my frames from the paper plans, so I'm *potentially* in the - will have to do a lot of fairing - category.

Although, all of the lines would have shrunk equally (I assume) so maybe the lines are all little smaller?

When I thought about it a bit - would the paper shrink in all directions? or just along the grain like a plank?

Just Wondering out loud..

[mmd]

I'll jump into the fray here, if I may. Paper patterns DO shrink, usually unpredictably in both direction and amount, but tend towards shrinking more along the length of the roll of paper and around 1-2% in length. That being said, the point of my previous comments on this in that other thread was not specifically directed at full-size patterns, but more towards scale drawings. The amount that a drawing will distort is quite small on a full size pattern for a reasonable size piece such as a frame or stem. It would be problematic if the paper pattern were ten feet long or so, but most patterns are much smaller than this. However, if one is measuring from a paper linesplan drawn at 1:24 (1/2" = 1'-0"), the error can be large. For example, assume a 48-ft lobsteryacht linesplan with the accomodations bulkhead location undefined. If the drawing has shrunk 1% and you measure from the transom to the forward bulkhead as being 36 feet, the error is:

36ft / 24 = 1.5ft (scale factor)
1.5ft x 12 = 18 (convert to inches)
18in x 0.01 = 0.18in (error due to shrinkage)
0.18in x 24 = 4.32in (scaled error)

So you will place the bulkhead 4-3/8" too far aft, which may cause difficulties in the cabin arrangements or engine compartment.

To reiterate - full-size patterns, properly stored, should not cause you any significant errors in construction unless they are of enormous size, but you should be very wary of dimensions lifted from scaled drawings on paper.

[Dale R. Hamilton]

Where do you get full-sized plans/patterns in those cases where the designer does not supply them- and the builder is unwilling/unable to scale these up himself? Will drafting companys do this for you or what?

[NormMessinger]

I called a company in Maine when I was considering the alternative to lofting Prairie Islander. The fellow heard what I wanted and said something like, to save on your phone bill let me begin by telling you our pricing starts at $4,000. I lofted it myself.

[G. Schollmeier]

Dale,

If you have a table of offsets and want full size patterns, anyone with a CAD program and minimal drafting skills can do the job for you. The key is to get the driver for the plotter that the plans will be printed with. The cost would be lofting time plus the sq. ft. of material you print on. Vinyl is about $1.00 psf, lofting around $50.00 an hour or a case of beer if you can get your neighbor to do it. If you don’t have the offsets you need to talk to a pro.

Gary :D

[mmd]

C'mon, guys! If you're not lofting you're not participating in the full experience of boatbuilding. If your knees and lower back don't hurt, you're not doing it right! :rolleyes: :D

[Dale R. Hamilton]

Ak- knee's and back- just why I didn't want to do it muself. Still, $4000...... gez

[Dalan]

Uh-oh... the full experience thing again! I suppose I have to fell my own trees and forge my own iron nails now, too? But... but... but... I don't have an adze or an anvil!

But seriously, thanks to all for the reassurances on the reliability of paper patterns.

Regarding accuracy and tolerances, well, I'll paraphrase a quote I heard once from an unknown source:

'A carpenter works to the nearest 1/4".
A cabinet maker works to the nearest 1/16".
A boat builder works to the nearest boat.'

Works for me!

[mmd]

First you plant a tree ... tongue.gif :D

[G. Schollmeier]

Dale,

First I agree with mmd, but if you hire it out I can’t see where it would be more than 3-5 hundred bucks depending on the number of stations. I’m trying real hard here not to solicit. Still that money might be better spent on a new tool or building materials.

Gary :D

[TomRobb]

In a previous kinder, gentler, age, Mad magazine had a piece about Yank-It kits. Rather than bore yourself silly and to avoid the cuts and bruises, there was a ring attached to string comming out of the kit box. You yanked on the ring and...FOOP! - the kit assembled itself - Viola!
No lofting required :D

[JimD]

I am working from full size patterns for a Glen-L 22 footer. The air here is almost always dry so the paper doesn't stretch or shrink appreciable and so far no problems that I know of. The plans also come with a table of offsets but Glen-L advises don't mix and match or try to correct the full size patterns by cross referencing from the offsets. Either stick to the full size or loft traditionally. And since I don't have a loft I'm placing my faith in the patterns
jimd