Fun with paper sails.

[aesch]

Getting prepped to make some sails this winter. Figured I'd try it first with paper, as it's cheap. Got a roll of 40# kraft paper from Staples, 24" by something ridiculous (400'?) plus some double sided tape. Also made a 26" board to curve the seam on the sail panel - adjust the curve, stick down panel #1, remove the curve, stick down panel #2. I'm using a #4-40 screw to bend the beam, so 1 turn is .025".
First sails I made were just single panel - looked ugly, curve put in at the foot didn't transfer well up the sail at all. Not worth measuring.
Second set used four panels. Both came out with definite shaping, but with room for improvement. For the jib, I used 2 turns for the lower seam going up to 6 turns for the upper seam. Midpoint of the beam located at the 1/3 point of the seam. Sail looked good, a bit flatter than I wanted and also with the camber further aft. For the main, I used 4T, 8T, and 11T (screw bottomed out) at the seams located at the 40% point of the seam. This sail came out perhaps a bit full at the top, again with the camber further aft than I wanted. I'll make another set tomorrow and see how they look.. Jib will have more camber, further forward. Main will have a bit less, also further forward.
This is fun! More fun than just buying a set of sails..
Now I've got to decide what curves to put into the luffs of the two sails.
I'm getting some cloth from Challenge as well as some tape (my son has an account there). Don't have it yet, so can't tell how it looks.

[aesch]

Made up paper panel jib #2 - didn't come out as expected. No real increase in draft and no shift in the max draft position. Hmmm...
Back to run some numbers - what's the shape of a deflected beam, and how much of that shape gets transferred into a seam (and where). Fire up Excel..
My seaming board is 26" overall, with 25" between the end screws. The screw deflecting the beam is in the center. Calculations show that for a deflection in the center of the beam (count the turns of the screw), the amount that goes into the fabric depends on the width of the seam. For an 18" seam, it's 59%. Continuing: 15" 43%, 12" 29%, 9" 17%, and 6" 8%.
More interesting is the position of max deflection as the paper/cloth is moved across the seaming board. For the material centered, max deflection is at the center - as expected. But for a 9" seam, moving the material all the way so one edge of the material is at the center of the beam only moves the max seam to the 44% point, and reduces the material added from 17% to 12%.
First conclusion is that shifting the material on the beam has little or no effect on the position of induced draft. I'll have to look into a jig that has the deflection screw at the 1/4 point rather than the center. Perhaps that will make a difference.
For the main, I can live with a draft at the 50% or 45% point. For the jib, I might have to hope that headstay sag will move the draft forward to the 1/3 point.
Son brought home the fabric and tape today. All looks good. The transfer tape is expensive! I'm looking forward to cutting it up and making some sails!
Al Schober #2065

[rs vernon]

Al,

The things you are writing are too technical for me. Pretty much zero comprehension. I sent you a private message the other day. One of the things I said was that when you deflect a beam that is supported at each end and has a single point of pressure causing it to bend, there is more bend at the point of pressure and there is very little bend at the ends. Sort of a parabola shape.

Scott

[aesch]

Scott,
Haven't found your PM - I'm new to this board so not quite sure where to look.
The stuff I'm talking about won't matter to you unless you decide to try making your own sails. If and when you do, you'll follow the same learning curve I'm on. Hopefully this info will help.
Best..
Al Schober, #2065

[aesch]

Made up a new bending beam this morning. The beam is only 18" long, 3/8" at one end and tapering down to 1/8" at the other end. Deflection screw is at the 1/4 point toward the thin end.
Made paper jib #4 using this beam, and it seems to be good. Carries 10% camber from the foot to the head with the max camber at about the 40% point. I think I'm ready to try a fabric jib. I'll make it about 1/4" oversize and then cut the luff, leech and foot after seaming.

[Jon Luscomb]

Cool thread.....waiting to see how it they turn out..

[aesch]

Some more info about the technique I'm using. Strongback is 3/4 thick, about 3" wide. The beam gets deflected by a screw through the beam. Lower panel is then bonded to the beam using double sided tape, the beam is then straightened, double sided taped attached to the lower panel, then the upper panel attached.
Variations are in: location of the screw bending the beam (middle or towards the luff?), location of the seam relative to the screw, and the end to end thickness of the beam (affecting its deflected shape). I've even changed the beam material from wood to PVC foam trim board to make it easier to bend.
I've made about 9 full paper jibs now, plus another 9 or so of just the upper two panels - basically trying to get the draft in the paper jib to move forward of the 40% point. No success, and the results are confusing - likely due to me not keeping adequate records.
Also tried two upper jib panel of sailcloth - a Challenge mylar/Dacron taffeta laminate. I'm not sure how to deal with the inherent curl in this stuff. As received, the mylar was on the inside of the roll, and that's the way it wants to stay. If I run the curl vertical, it seems to dominate the shape of the jib - probably want to run the curl horizontal? Also, the tape seems to bond to the mylar side much better than the taffeta side - arrange the seams so they're mylar to mylar?
The further I get into this, the more I realize I have to learn.
Perhaps just buy a set of sails? Naaah...

Al Schober
#2065

[aesch]

It's now April and the new boat has had it's first sail. Let you know how I got from cutting paper to here.
Bought Larry Robinson's sailmaking booklet - well worth the money! First revelation was that all the panels don't need to be the same width (Duh?) - put the seams where you need the shaping (ie: toward the top). Narrow panels up top, wider panel toward the foot. Second revelation (which I think I suspected) was that you can't hang a sail horizontally in the shop & evaluate the shape. Gravity acts uniformly across the sail - wind doesn't!
I made the decision to stop cutting paper and start cutting cloth. My first jib was from a Challenge mylar/taffeta laminate, and I didn't like the results (too baggy) or working with the material. Second jib I used Challenge DPL62N60 - kinda like a dacron ripstop. Looked good to put on the boat for a trial, so I made a main using the same material. Also looked good for a trial.
Oh yeah - didn't use Robinson's blocks. I stayed with the beams - ended up with a 20" and a 10" beam. It's easy to determine (math) how much of the deflection of a 10" beam will end up in a 7.5" seam. Guess the broadseam for a given seam and just work back to the beam deflection. No need for a whole woodshed full of seaming blocks.
Anyway, boat hit the water today and looked good! In an hour of sailing, the only tweak was to flatten the foot of the jib a bit. I'm good to go for the R1CR in Stowe!

[aesch]

Thought I'd post some photos of my home made sails. This were taken last weekend at Spring Lake (nice venu for sailing).
First photo shows things with about 2# tension on the backstay - looking pretty good IMHO.

Day 1

2065_07em.jpg (241.47 KiB) Viewed 24099 times

Next try might be for a bit more camber up top. Notice the lack of jumper stays - I'd pulled the jumper wire out of it's swage while sailing in white cap conditions with the A rig. Rig was good enough to beat Dave Ramos in one race!
Second photo is the second day - a bit more wind and a bit more backstay tension (maybe 4#). Here the main has turned itself inside out. Mast deflection at the spreaders is probably about 5/8", while the main was only cut with a 1/4" luff round.

Day 2

2065_08.JPG (208.78 KiB) Viewed 24099 times

Next try on a main will be with more luff round and a bit more camber up top. What I'm going to do is measure carefully the mast deflection with 4# on the backstay and no jumpers - then cut the luff to that curve. I could explain my guess of how it will sail, but that would spoil the anticipation.

[AugustusF]

Made up a new male fertility pills this morning. The beam is only 18" long, 3/8" at one end and tapering down to 1/8" at the other end. Deflection screw is at the 1/4 point toward the thin end.
Made paper jib #4 using this beam, and it seems to be good. Carries 10% camber from the foot to the head with the max camber at about the 40% point. I'm ready to try a fabric jib. I'll make it about 1/4" oversize and then cut the luff, leech and foot after seaming.

Sails looking great. You did a great job Aesch. Thanks for sharing all the detailes.