Looking for sail plans for a Nutshell Pram

[gdimaine345]

My 14 year old daughter and I are partway through building a 7'7" Nutshell (we did the laminations and cut out parts over the winter, and now we're set up on our back porch with the garboards on).

So . . . my wife was watching us the other day and asked what we are going to do about a sail, since we're building the sailing version . . . I suggested a kit, but my wife is a serious sewer (e.g., she's designed and made curtains, slipcovers, a custom wheel cover for the sailboat, etc.) and was thinking about doing the lofting, cutting and sewing of the sail with my daughter.

Has anyone seen anything that would help her with this -- other than the sketch that is part of the building plan for the pram, I haven't been able to find any more detailed plans or instructions.
Anyone seen anything or have an idea where to look?

Thanks,

Tom

[Thorne]

http://www.woodenboatstore.com/images/300306S.JPG

Sailmaking, and in particular sail-design, is a fine art -- not something you can pick up quickly.

A kit from Sailrite is the best idea, and if she continues to be interested she should buy the book above from our kind hosts. I'm sure there are other books that will be recommended.

http://www.sailrite.com/Categories?search=nutshell
http://www.sailrite.com/core/media/media.nl?id=7388&c=603010&h=613a64f21b4ad0e2b275&resizeid=-1&resizeh=100&resizew=100 (http://www.sailrite.com/Nutshell-77-Lug-Main-Kit-Cream-Dacron) Nutshell 7'7" Lug Main Kit Cream Dacron (http://www.sailrite.com/Nutshell-77-Lug-Main-Kit-Cream-Dacron)
Nutshell 7'7" Lug sail made from 4 oz Cream Dacron using the designer's plans.
Leech and foot finished with double folded hems. Can be made on a home sewing machine.
$175.00
Item Number: 1191C

[Cuyahoga Chuck]

Here are some comparable sails but not the one you are looking for;
http://www.boat-links.com/Sails/index.html
I sail a D4 dinghy and a ready made spritsail from Mertens (a Mack) cost me $205. I chose a ready made sail because a boat with such a short waterline will never be fast and I felt I had a better chance of getting all the hull could deliver if I had a professionally made sail. It doesn't seem rational to talk of speed for such a small boat but, it is important. Small lightweight sailboats don't have much mass so they lose speed very fast. I found my boat had trouble going from one tack to the other if I was daydreaming and let my speed decline.

[StevenBauer]

Tom, are you far from Portland? We could get the girls and their boats together sometime. :)

http://www.woodenboat.com/forum/showthread.php?t=80582


Steven

[Todd Bradshaw]

First of all, the price on the Sailrite kit is pretty good considering that their computer has already done all of the design work and cut out the panels. Assemble it following the guidelines printed on the cloth and you will have a nice sail. I just started a pair of lugs with a main of similar area and a 15 sq. ft. mizzen and paid $123.30 plus shipping for the fabric alone at wholesale price. The cloth I use is a little bit fancier than the Challenge 4 oz. in the Sailrite kit, but the Challenge cream is still quite decent sailcloth.

These little vertically cut lugs aren't particularly difficult to scratch-build, but when you haven't built a few previously to get a feel for shaping them they can be a little bit tricky. There really aren't any books that will tell you as much about how to actually put the shape into one as you would like to know when you're in the middle of the project and you just have to develop a feel for shaping them with practice.

Here is the plan for the pair I'm building: The main is around the same size as the Nutshell main, but slightly taller and narrower with a little higher peak and a loose foot. This is the same basic Oughtred-style balanced lug that I built for Steven for their Elf, which is one of my favorite lug profiles and looks good on just about any boat (where is that cool fog photo?).
http://webpages.charter.net/tbradshaw/RAKE.pdf

And here is the lofting on the floor to build both sails traditional-style without the aid of a computer plotter - pretty much batten, masking tape and string work and the most high-tech part of the project so far is the adhesive on the back side of the masking tape.

http://webpages.charter.net/tbradshaw/sail%20const.%20007%20copy.jpg

The location of the corners comes straight from the sailplan. The luffs are straight with no luff curves. This is because these sails are so small that even the 4 oz. fabric is proportionally so stiff that trying to build draft into the sail by adding luff round doesn't work very well. It just makes a hump on the luff and that extra round area never seems to find it's way into the body of the sail. Lugsails also get double-taped luffs for better strength around here, so for their entire lengths, the luff edge of both these sails will end up being at least five layers thick. Considering that a lot of folks tend to run pretty high downhaul tensions on their lugsails, five layers gives the edge some pretty nice beef. Corner patches at the throat, tack and any reef tacks (these sails won't have reefs) would add an additional four layers in those areas. I don't fool around when it comes to reinforcement.

The foot round is added by eyeball. You want a pleasing look without ending up with too much of a flap hanging off the bottom down there. During the shaping, this extra round area and neighboring fabric along the sail's bottom will be transformed into a slightly cupped shape so that the foot doesn't flap in use. The leech edge is hollowed about 1" for every 6' of its length to keep it from flapping as it ages. For this main, it works out to about an inch-and-a-half of hollow, centered at mid-leech.

On a sail this size, I'll generally add about 1.5"-2" of round along the head as well. Maximum round amounts (both along the head and also the foot) are located about 45% of the way aft of the luff. The head round has two functions. It puts a little bit of draft in the upper part of the sail and it helps allow for the bend that is likely to happen on small-diameter, somewhat flexible yards when sailing. Bend tends to reduce draft and can quickly eat up any draft you added to the design, so assuming that yard bend is going to be a reality, adding a little more round to allow for it tends to be a pretty good all-around compromise.

The perimeter of the sail is set out from the sail plan using pins and string, the rounds and hollows are added by bending battens and the actual final perimeter shape is then lofted out with masking tape. I usually hem the leech edge and allow for that extra cloth while laying down the masking tape. I bind the head, luff and foot edges (rather than hemming them) as I like the way the binding sits down on the curves better than a double-rolled hem. This will be done with separate pieces of cloth, so there is no extra allowance added along these edges. Other sailmakers may prefer to work with hemmed edges and do it differently but either method can work.

So now we have a perimeter, but our sail is still flat. We've essentially made a plan for a couple funny-shaped tarps. The next step will turn them into a three-dimensional airfoils. We're going to do it with the aid of those curious V-shaped tape lines at the top and bottom of each sail's lofting.

Dinner time - more to follow.

[Todd Bradshaw]

Most lugsails are vertically cut (like the little Sailrite drawing above). The panels and panel seams run vertically and are placed parallel to the sail's leech edge. By orienting the weave to the leech we prevent as much fabric stretch as possible along this long, unsupported edge. The fabric panels we will use are straight-sided slabs of Dacron. The seams are simple overlaps, secured with basting (double-sided) tape and then sewn, and for small sails, the panel-to-panel overlaps at the seams are generally in the 1/2"-5/8" width range. The transformation from a flat sail to a 3D shape will be done by monkeying with the overlap amounts at the panel seams.

If we made a consistent 1/2" wide seam joining two flat panels of cloth, the result wouild just be a wider hunk of cloth. However, if we keep the seam width 1/2" for the center of the seam and then gradually widen the overlap at the ends of that seam for a couple of feet, we will have created a hunk of cloth that is wider but no longer flat. It will have a little bit of a cupped shape at the ends. This is the principle that we will use on the sails. By carefully and gradually increasing the panel seam overlaps as we approach the head and foot edges of our vertical seams, we will hopefully wind-up with one big, slightly-cupped hunk of fabric. Sailmakers call this shaping technique "broadseaming". We don't just want any old cup shape though, we want a fairly specific cupped shape. The shape that we produce will be the product of where we begin increasing the overlaps and forming our broadseams joining our panels and how much increase in seam width we use as well as how many of these shaping seams we incorporate into the sail.

The V-shaped tape lines on the loftings are the "broadseaming guides". As a panel seam reaches these lines at the top and bottom of the sail, the sailmaker will begin the gradual increase in the seam overlap. The deepest part of the V will indicate the area where I want maximum draft for that section. They're generally around 45% aft of the luff and are placed by eye. As far as I know, there are no specific written formulas that tell you exactly where to put these things or how deep to make the V. It would also vary with the firmness and stretch characteristics of the particular fabric you're using, so it's something you learn over time by making sails (That pre-designed kit is looking better all the time, isn't it?)

For small sails like these, by the time I get to the head or foot edges, each seam overlap will usually have increased by 1/4"-1/2" or so. Bigger increases result in deeper cupped shapes and more sail draft. Smaller increases result in flatter sails. A lean boat that accelerates quickly will usually sail best with a sail that has pretty shallow draft (flat-ish). A beamy or heavy boat needs more power to get moving and to punch through chop. It will usually benefit from more draft. This is another consideration to account for when laying out the draft and broadseaming.

In order to shape using seams, we have to have seams to work with. The standard 36", 48" and/or 54" widths that Dacron comes in would not give us much potential for broadseaming on a sail that is only six feet wide. Two panels and the entire plan would be covered! We can make a smoother shape by using several narrow panels and small broadseam increases at each panel seam, rather than use two or three panels with big, wide broadseams. So, by splitting the cloth into strips that are maybe only 12"-18" wide, we can generate more seams, more opportunities to build-in subtle shaping and a better sail (it also looks better).

As we baste the panels together with basting tape over the lofting, we do it so that the center sections have a nice 1/2" seam. When we come to the V-shaped broadseam guides at the top and bottom of each seam, we start the gradual overlap increase as we head for the edge. The last few inches we give the overlap just a hint of flare (increase) which helps make a nice firm edge out on the water. Each broadseam makes the sail slightly smaller (dimensionally) so we cut our panels slightly oversized, do our seaming and basting, lay the basted sail back over the lofting and re-mark the corners and edges to match the lofting and keep the sail the proper size.

So essentially, that's the process through the lofting stage and well up into the construction phase. Most of the rest is just doing the work. Unfortunately, even with Marino's excellent book, the design phase is not well documented or easily reduced to calculator and measuring tape work for this type of traditional sail. Much of it is something you learn through practice and repetition. That's the biggest problem for most beginning builders: learning how to make the proper allowances needed for sail shaping. This also points out the beauty of the sail kit approach. You can be the builder or assembler without having to also be the designer and make all those judgements.

The computer works a bit differently when it designs a sail. Rather than making a sail with straight-sided panels and shaping it with variable-width seams by hand and eye, the computer can accurately see the sail in three dimensions, milimeter by milimeter. It builds the sail conversely by using constant seam widths everywhere and gets the shape by cutting the panels themselves into curved shapes. The finished sail and the sections of the panels between the seams may have basically the same shape, but the method used to produce that shape is different. It's amazing what a couple hundred thousand dollars worth of hardware and software can do.

[wtarzia]

I have the 37 sq ft Nutshell sail, and the 54 sq ft Shellback sail is in the mail due to arrive any day now (trying a yawl rig for my outrigger canoe). If I can take some kind of measurement off either of these sails to help you, let me know. I don't know too much about sail technicalities, but I assume you could explain what you need easily enough. -- Wade

[gdimaine345]

http://www.woodenboatstore.com/images/300306S.JPG

Great idea . . . I have seen this book before but had forgotten about it . . . thanks!

[gdimaine345]

Tom, are you far from Portland? We could get the girls and their boats together sometime. :)

Steven -- We're on Great Diamond Island, just a short ferry trip from Portland. My daughter was quite excited to see your photos of another father / daughter team building a Nutshell. Are you nearby?

Tom

[gdimaine345]

These little vertically cut lugs aren't particularly difficult to scratch-build, but when you haven't built a few previously to get a feel for shaping them they can be a little bit tricky.

Todd --

Thanks for the great postings on construction. They go to the heart of the questions I had about how to build the right shape into the sail. My wife read your comments and they immediately made sense to her, I think both as a sailor and someone who sews. One of the points my wife has always made about sewing is that it is inherently a 3D operation that you learn over time -- how to use a combination of cutting and seaming to create the shape you want. BTW, the lofting photo is particularly helpful.

The decision on kit versus DIY may turn on how much she and my daughter want to take on together this summer.

Tom

[Todd Bradshaw]

Panel basting underway. The fabric is 4 oz. Hayward Tanbark split into 12" wide panels. This fabric has the nicest color and most cotton-like surface texture of all the tanbark Dacrons I've tried and a built-in UV absorber, so it's good stuff. I pay about $1.35 per square foot for it wholesale, so you don't want to waste any more than you absolutely have to. The basting tape is 1/2" Venture tape which is very high tack yet resists bleeding oily stains into the cloth better than most that I've used. Tanbark colored cloth is a bit harder to work with because you can't see the lofting as well through it as you can with cream or white fabric.

http://webpages.charter.net/tbradshaw/sail%20const.2%20001%20copy.jpg

Here are both sails - basted, broadseamed, trimmed to shape and ready for long-seaming on the sewing machine. Leech hollows are yet to be cut. I'll do that after the panel sewing and corner patching when I'm actually ready to put the leech hems in. The lofting is no longer needed and has been peeled up before the masking tape bonds to the floor and becomes hard to remove.

http://webpages.charter.net/tbradshaw/sail%20const.2%20007%20copy.jpg

Did I happen to mention that this process is hard on your knees? At 56 and with about 28 years of working on sails and/or balloons, it gets harder and harder to get down and crawl around on the floor with every new sail. You would think that when picking a career I would at least have chosen one where I could sit, stand or otherwise adopt a position suitable for a higher primate, but no, I decided to build sails instead.

http://webpages.charter.net/tbradshaw/sail%20const.2%20005%20copy.jpg

[gert]

Todd; please :eek::eek::eek: ; and I just had breakfast...

Excelent instruction till the last image ;)

[Todd Bradshaw]

They still look better than Dingo's knees.

[BillyBudd]

"Sail Making for the Home Boatbuilder" by Paul Fisher of Selway Fisher Design, in England. (I think they've got a website although I ordered once from a remote island in the South Pacific and got it -- all by snail mail.) It is a short, 50+ page pamphlet that lets your wife (you?) noodle her way into the world of sails with useful rules of thumb. More likely to result in a sail being designed on the kitchen table and being built than "Sailmaker's Apprentice." I've often thought that a small boat, a dinghy, might just be the place for an amateur to design/sew up a sail.--and I know the experts say this is just the place one needs an expert. This isn't an economic decision, but on something so small (presuming non-competitive spirit) built 100% by self, isn't it possible to DIY? Out of cheap stuff (tarpish kind of stuff--Tyvek? Typar? with tape and/or staples?) to see how it sails, then on to better material. If all that fails, Sailrite kits have impressed me to no end--have watched wife sew up 3 of them. T

[StevenBauer]

Tom, are you far from Portland? We could get the girls and their boats together sometime. :)
Steven -- We're on Great Diamond Island, just a short ferry trip from Portland. My daughter was quite excited to see your photos of another father / daughter team building a Nutshell. Are you nearby?

Tom

We live right in Portland, Tom, and Talisman is moored at East End Beach. We could sail over with Amulet in tow for your daughter to see. You could come for a sail, too. :)

Steven