Repairing the Mast of Terra Linna where it has delaminated.

The delamination split is a worry and yes I have seen it. I think it goes back to when T/L was caught in a strong SW blast at a Regatta Sail Past following an AWBF.

We broke the boom jaws and spreaders which possibly sprung the mast. The John Leather “Gaff Rig Handbook” mentions “… suddenly fails in a hard blow it may also damage or spring the mast”. However, we did not see the delamination but it has possibly opened up with time. We replaced the jaws and fixed the spreaders without taking the mast out hence the mess around the spreaders cheeks but that is cosmetic and easy fixed. We just need to clean up the Sika on the Cheeks and mast, then mask it up and reapply Sika to a neat finish. I am fairly confident the spreaders are firmly fixed to the mast but please check this?

We do however, need a bit more to do with the delamination and reinforcing that area without anything metal that aids rot and water ingress to the mast. I have re-though my comment about using dump pins and also I heard some one suggest a metal gusset. The one issue with masts is to make sure all potential water ingress is minimised to prevent weak spots and dry rot in the mast. S.S. Gussets or Bands will hold water underneath them and cause dry rot over time.

So I suggest the solution is once the mast is back to bare wood;

  • Clean out and vacuum the delamination crack.
  • Make at least three clamping blocks as per the attached drawings.
  • Purchase some 75mm Kevlar or Carbon Fibre tape, enough for at least three rounds per bandage as per the drawings. Making sure there is one under each strop placement will also double to prevent chafing as well as holding the mast delamination together.
  • Once all cleaned up and dried apply some epoxy to the delamination gap then apply the clamp blocks. Where the clamp block go over the delamination gap apply some Vaseline to the blocks. This will work as a release agent.
    • Then where the bandages will go apply a thin coat of epoxy and then wrap the bandage for at least 3 rounds. The epoxy should hold it in place. Apply a thin coat of epoxy over the bandage, do not over do it with the epoxy.
    • Then layer the strip over the delamination gap by applying a thin coat of epoxy over it first then lay the strip into the epoxy. Once the strip has adhered give it another light coat of epoxy.
    • Each day for 3 days rub the bandages and strip back lightly, clean it with acetone. Then apply another thin coat of epoxy.
    • Do not oil the mast until this work is complete.

This remedy should allow the mast to serve us for a good few years.

11 Responses

  1. I was one of the crew on TL at the AWBF and it was the the gaff jaw that was broken. Whilst there was pressure put on the mast I don't believe that this incident has been the cause of the split. When I first inspected the mast when it was removed and looking at Bernies photos it appeared to me to be a separation of the timber which appears devoid of glue. If it was glued with the west system there would be splinters of glued pieces of failed timber on the sides of the split yet the split doesn't show any apparent timber or glue failure. This leads me to believe glue was never applied to this small section of the mast during construction. It has over time, opened due to the ingress of moisture and was exacerbated buy screwing the Gaff crane and fore stays cleat in the unglued slit.
  2. Hi All. There appears to be two aspects to this problem, the fisrt is repairing the split with a similar method used for the bowsprit and the second is reinforcing the area around the cleats with bands. Peter had a few sugestions in the topic "Adhesives and Glues to use in wooden Boat Building and restoration." in the gereral discussion section Is the mast constructed with the birdmouth method as this may affect our repair method. Just a few thoughts for Thursday.
  3. I agree the slit should be cleaned, epoxied, wrapped in gladwrap, clamped and then bandaged. I'd use glass bandage in the bands and cover strips as you don't want grey or black patches on the mast. My suggestion is don't incorporate any silicons, or oils as they affect cure of epoxy resins.
  4. Thanks for all the input. I have been through my records and came across the design plans by Murray isles which I attach for your information. Also I add a photo of the mast taken today with a line through the CL indicating movement in the top of the mast. Although slight it is indicative of some spring in the mast. It will always be difficult to know which came first the spring or the split. Yes the cleat screws could have contributed. If we epoxy the mast above and below the bands I think we can abate water ingress. I will post the photos and design plans. I have also taken a call from member Bruce Jessup who has made these comments based on his experience with epoxy over many years; • Don’t use Kevlar or Carbon Fibre tape • Use multi directional bi-axial cloth but definitely use epoxy • Peel Ply for a better finish on the bands. He is going to send me some we can use. • And definitely vacuum bag the repair.
  5. Bernie's photos help. The split appears to align with the cleat screws, which could be what started the problem.
  6. Silicone baking paper (aka "Glad-bake") works well as an easy-release protective layer between surfaces that you don't want glued. It has the advantage that there's no additional sticky or oily component left on the timber. Jim Bonham (who was a paper industry research scientist before retirement) looked into this closely when building "Velella". His comment to me at the time was that you have to use the name brand baking papers - the cheaper ones don't necessarily use silicone.
  7. Peter As it turned out and unfortunately I did not have a good look at the area that needs repair. i took it as a slit in the mast rather than a delamitation. I would take a delamination as a break down between laminated surfaces eg glued surfaces. A split may have nothing to do with any particular incidence but is what timber is prone to do. (currently dealing with the splits in the Green Dinghy planking). Anyway I agree the task is to keep out water ingress and to not use metal in any permanent repair. I thought the split was above the throat jaws of the gaff. If this is the case I would expect a glued repair would be sufficient without the reinforcement of the carbon mat/epoxy bands and possibly to not clamp, but just fill the crack with neat epoxy, and subsequently with epoxy with glue filler. if it is more extensive then I agree with the bands. If using clamping blocks of some description packing tape is probably better to use instead of a release agent. For the area of the bands we would need to be careful that water can't get in under the bands. just some thoughts Rob
    • I agree with Rob and Bernie. The cleat above the spreaders has twisted and caused the split in the mast I think a fillet of timber in the crack would be strongest and in line with traditional repair methods, then wrap with kevlar or carbon fibre to strengthen it Maybe we should be thinking about why the cleat the cleat twisted in the first place and try to prevent it happening again. Putting a layer of the wrapping behind the cleat might reduce the tension on it....
  8. Hi Peter, That looks like a good solution to me. David.
    • Rob and David the slit is probably over a metre long and runs just below the cross trees to well above the cross trees. The day of the regatta sail the whole rig was severely challenged and we were lucky to get away with the damage we did receive. On reflection I think the breaking of the jaws on the boom put a lot of stress on the mast. Because the damage is aloft I believe the bands will serve us well.

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