Sail: 2003 North Marathon 3DL - Repair

[rgleason]

The two outside Light Dacron cruising UV protective tafetas are gradually becoming de-laminated as the adhesive is letting go.

The inner vectran threads remain adhered to the center mylar throughout the sail. There appear to be no loose strings. Therefore it appears the "racing" 3DL part of the sail is intact and only the loosening tafetas are the problem, during roller reefing etc.

Options:
1. Cut the dacron tafetas off with sharp scissor on both sides and use the "racing 3DL part of the sail in July and August until it fails somehow due to "bag of strings" delam or UV failure.
2. Sew a straight seam horizontally across the sail, securing the exterior tafeta, along the center of the 3 draft stripes. Then sew two more straight seams across between each draft stripe (approx 3' between seams). This will secure the tafeta to the sail and the tafeta will continue to protect the vectran and mylar. The sewing holes will provide a way for entraped air to get out when we roller furl and the tafeta will not become a second or third sail when it becomes fullly delaminated.

We could possibly add 1-3 years to the 13 seasons already.

Any suggestions? Advice?
What thread should we use?
Should we put a 1" wide sticky dacron tape under the seams where we sew so that the light tafeta does not pull out or rip along the seam?

Thanks.
Rick

[rgleason]

Nick D. from North Sails advises:

..its likely to continue to delaminate...I can't comment on a good repair strategy until we see the sail in person and can assess it properly. The repair methods that you mentioned are fairly unconventional and I wouldn't recommend. The inner mylar films used in marathon sails are not the same as the films used in the 3DL race sails. They tend to be a little lighter and not designed to be used on their own. This is to help keep the weight down and it has the protection of the taffeta. I also fear stitching into aging taffeta with nothing on the backside is not going to last. We typically add a layer of sticky back to the area to give the thread something to grab onto. This can work, but can also be expensive. Until we see the sail we can't put together a real plan.

Note: I was planning to have it sewn with straight seams along the middle of the draft stripes. Then for the intermediate horizontal seams between draft stripes use some dacron adhesive tape on each side and sew down the middle of that. The old tafteta would then provide UV but no strength.

Nick points out that the middle mylar is lighter because the dacron taffeta on each side took some load, so since that is loose, the Vectran thread and Mylar laminate remaining is going to deteriorate faster (tafeta is no longer structural).

I am going to have to think about this a little. Any suggestions?

[poiu]

Would it be possible to cut a small hole to enable you to access the back side of the taffeta? then to inject a thin flowing adhesive in there with a syringe and a long tube to get to all areas. Press together and hold flat.

I expect to have this problem at some time, so I would like to hear how you deal with it.

[rgleason]

I initially thought I could squirt 3M 5200 and smush it, but this is a huge messy project and 3M cured is too inflexible for the center of the sail. It would cause too much shear stress on the tafeta laminates and we will be chasing the delamination.

Yesterday after hanging and washing the sail, we were finding that it is becoming a more general failure, so we need a temporary 1-3 year solution to prolong the life of the sail, but the sail is failing now due to delam of the exterior tafetas which we are told are structural and UV protection.

One question is, if we sew straight seams on 1" wide tapes (both sides) horizontally every 3' (vertical measure) to hold the failing exterior dacron tafeta in place as UV and structure, will the center mylar and fully adhered vectran strings continue to work without direct bias support from the exterior tafetas?

We have been told that the center mylar in Marathon 3DL is thinner than a racing 3DL because the Marathon has two additional exterior dacron tafetas.

So, is it going to be worth the cost to try sewing horizontally, if that center layer is thinner?

The center mylar and vectran threads appear to be in good condition and fully adhered, albeit 13 seasons old.

Mylar gets brittle over time and UV exposure, and fails rapidly when it reaches its lifespan, but it has been protected by the tafetas.

[davecalvert]

First, 12 years is a long life for a laminated cruising sail. We have had many clients replacing 3DL sails after much less time. This is a good life.
It sounds like the delaminating is extensive. It would be difficult to stitch the loose taffeta to the interior scrim without causing bubbles and distortions.
Using a two sided seam stick would help but, how would you you get this inside between the layers?
I think it is time for a new sail.

[rgleason]

Dave, thank you. You've posted several very helpful comments responding to my questions while working my way to a new sail.

This morning I called Aaron Norris, Custom Canvas in Mystic, CT. He made our mainsail years ago, and has been our sail repair person for 25 years. I usually listen to his advice and experience. Aaron repaired the UV degraded leach last winter and told me it was delaminating then, he said it would become a "bag of strings". I am usually optimistic about sails and thought that would be a couple of years more.

This morning he advised that he would have to sew the sail at at least 1' intervals and even then the tafetas will not be contributing to the strength of the sail and the new sewing threads are not intended to provide the necessary shear after the adhesive has failed, so he thought the 4-6 hours of work would be a waste of money, particularly with the mylar being thinner.

Accepting the fact that one of my favorite sails (great shape holding) is now bag material, and that my Marathon 3DL 95% is on the way to the same use. I discussed what the new sail should be. He had originally suggested I look at a Hood Vektron Sail. After educating myself about all the different sail cloth, cuts etc now available (from expensive load path to radial laminates/dacron to simple dacron, and getting prices from a number of lofts, it have come to the conclusion that I am not going to want to buy another new sail for a very long time and we will only do 1-3 races per year (at most) so the requirements have changed a little. Less shape holding needed, greater longevity, less mildew prone, best dacron cloth available with a miter or crosscut.

I really like and understand the loading concept of the Mack miter cut jibs which puts the fill threads aligned with the the split load path of the jib sheet along the foot and the leach. This cut made a lot of sense to me since we tend to have to roll this 140% jib up a lot when the wind gets above 12-14 knots. (The jib is the equivalent of 156% on a standard Bristol 32). Their price was very reasonable and I liked their sails, as seen at the Newport Boat Show. I agreed with Travis's description about the load path and the fill alignment of a miter cut sail. The Hood sail is considerably more expensive.

So I asked Aaron if he had worked on Mack Sails and told him that we had settled on Challenge Marblehead Low Aspect 6.77 oz for the quote. Aaron said he had seen Mack sails and they were reasonable but the mitre cut is an older cut and is not necessary. They both work, and can be furled to 25% for shape and beyond to get home. We had some short discussion about Radial Cut because I said furling them changed the load path from what was designed, more so than miter and cross cut. Aaron said they could be furled to 20% and all cuts get puckered at the corners if furled greater than the designed point, to get home.

I asked Aaron what material he would use. He said Hood Vektran, saying something like it is "bulletproof". This was interesting to me because I had been studying cloth and in particular looked at the Kuraray Vectran engineering specs. Vectran HF degrades to 30% strength with 400 hours of UV. Vectran HF does not shrink as much as Dacron, so they have to preshrink the Dacron in the fill direction which is the direction of the Vectran too. Then the warp threads are fully shrunk with the 104 High Mod fibers. Hood changed to Challenge Looms when the old slow very tightly woven Irish mill went out of business about 2008. I believe the quality is just as good because the 104 fiber has more stretch during the heat treatment which really tightens up the fabric. What this means is the warp threads shrink more around the fill threads and I believe the thickness of the warp and fill is pretty close. I am told the vectran threads which are about 3/8" apart are protected from UV by clear warp threads. After studying vectran I was not convinced about using it with Dacron and some said it was just a marketing ploy, but Aaron's enthusiasm for the Hood cloth and the quality of the Hood sail are all very strong factors to consider.

Anyway, during the conversation Aaron said the sails are very well made and he wanted me to come see some very old sails that just came into the loft for end of season check. Which we will do next week.

[poiu]

Aren't you worried that Vectran is only 30% of its strength so soon after new. What will it degrade to over the years following?

Why not have a go at gluing your sails?

A search on websites shows Bostik recommend either acrylic of cyanoacrylate industial adhesives for polyester. Henkel recommend 401 prism and 414 super bonder and others. Dow's Rohm and Haas have adcote 122hv. Try 3m too such as VHB tapes or Scotchweld DP 460 etc.

You could get technical help from the producers directly of course.

[rgleason]

Poiu,
Yes I was worried about the UV degradation and the fact that the Vectran shrinks much less than Dacron when post treated under 400 degree heat lamps because the vectran threads would not be loaded after heat treatment. I will attach a document with this dialogue with Kuraray and then Hood.

Your ideas for glue are interesting. I think my attempts at gluing it will be pretty feeble and very messy. The things that convinced me to go with Hood Vectran was anticdotal reports here in cruising forums, our sail repair person since 1991 and Joe Copper's response in the attached.

[poiu]

Good luck with the sails. A difficult choice. You could do a post to ask for people who have them for feedback.

[rgleason]

New 140% Roller Furling Genoa approximately 364 sf. with stanchion and spreader chafe protection, sail numbers, 3 draft strips, leach and foot cords & uv cover. Mostly Fall Boat show pricing.
There are many good sailmakers with good sails with a wide range of choices! For our Cruising purposes we were torn between Hood and Mack, although UK offered a good sail too.

Far East 2460 Full Radial 7.11 Challenge Warp
Hood 2900 Crosscut 6 Hood Vektran Challenge
Mack 2370 Mitre Cut 6.77 Challenge Marblehead
North 4110 6 Norlam Tour XI White
North 4560 3DL Marathon 600
North 5110 3Di 760M
Precision 2240 Radial Flexible Mylar Taffetta (like Norlam)
Precision 2880 Crosscut Vectran Cruise Laminate
Precision 2750 Radial CDX Polyester Cruise Laminate Zig Zag
Precision 5050 Radial Hydranet Dimension Polyant
Quantum 4400 TriRadial Warp Drive 9.11
Quantum 6200 MC6500 Performance Cruise (like 3Di)
Quantum 8700 MC6700 Performance Cruise (like 3Di)
Rolly Tasker 2200 Crosscut 7 Challenge
Rolly Tasker 2650 Triradial 7.11 Challenge Warp
Rolly Tasker 2730 Triradial 7 Challenge Cruise Laminate
UK 2660 TD Passagemaker II Crosscut P2ML 3.7oz w FG Tapes

[estarzinger]

Mmmm. . . . Thread not fresh and you may have moved on to other problems . . . . But one tip for laminated sail repair - you can sometimes "relaminate" them . . . . Put a towel down flat, lay delaminated part of sail down on towel, put another towel on top, and then slowly iron it, starting from a laminated section going into the delaminated section. This can often reactivate the heat set glue.

If you look around a sail repair loft you will usually find a couple irons tucked on a shelf, and they have been known to do this to fix minor laminate problems on new 3dl's.

[rgleason]

Evans,
Thank you for the idea, very interesting! We still have the sail, but have ordered Hood for next summer.

I'll try the iron. There seems to be a complete general and gradual failure in the Genoa. It might also help extend life for our 95% Jib which starting to delam but is better than the Genoa. They both still have good shape and the aramid threads are still attached.

Do you know what approximate temp would be best?

In the list above I missed the $ and oz so it should be this for example,
- Hood $2900 Crosscut 6oz Hood Vektran Challenge

[estarzinger]

You want to get the adhesive to 110-140F. So, ironing thru a towel you need the iron somewhat hotter than that. I have heard 200F iron and moving the iron around suggested . . . . But I think most sail makers do it by feel and touch "not too hot" being the operative description.

It should work so long as the adhesive is relative clean.

[rgleason]

Thank you!