Sailor Thom Davis shares how he solved a problem often associated with folding trimarans. Namely, the lack of an easy method to tension and de-tension mast shrouds in between the folding and unfolding of the boats.
He explains what he is now doing for his boat below. A great write up and video here … and many thanks for sharing it with us!
Thom writes:
Hi Joe.
One common issue with folding trimarans is the likelihood that the shrouds must be tensioned and detensioned each time you fold and unfold. Furthermore, there is a similar likelihood that you want to have the mast centered and you want the shroud somewhat tight to help keep the boat stiff so you can point. Most modern small trimarans use dyneema shrouds with an adjustable lashing to achieve this but that entails a lot of tangles and knots and once you need to untension, the knots are difficult to undo without a marlin spike–and basically it takes a lot of time and bother-each time.
My boat, SriRacha (SeaRail 19) came with the basic system…shrouds short and lashings to the chainplate. Truly a bother. Difficult to get the mast centered and difficult to tension/detension.
After a couple years of dealing with this, I finally created a “no knot” system with variable lashings. It uses Ronstan Shocks to create a cascade. Mine is 8:1 to give a good tension. When you make the shroud, instead of a sailmaker’s thimble, you thread half the Ronstan Shocks onto the end for the chainplate. For my boat, since the chainplate is not accessible under the tramp, I made a continuous loop of dyneema with the other half of the shocks onto that loop. Get the mast centered and mark where the lashing line comes through the final shock. You will create an eye splice there. Then you luggage tag (with an eye splice) the remainder of the lashing line there. To tension the mast after unfolding, simply pull the lashing through to the eye splice and insert a soft shackle luggage tagged to the eye. Now the shroud is tight, the mast is centered and you have a handle to pull when you are ready to detention.
The first minute of this video shows the system.
Thom always comes up with the most innovative solutions
Thanks…I’m just lazy and impatient…so I find ways to make things easy for me.
I get how the tensioner mechanism operates (like a block and tackle) but don’t understand how the tension is locked and held in place once that tension is developed- the written explanation speaks of “luggage tagging” and soft shackles but the video doesn’t show the act of locking the tension in place and only shows a metal clevis pin already in place and being used to “take out the slack” which doesnt sound like the same thing as holding the shroud under tension.
Never heard the term “luggage tagging” in this context but if I had to guess I would guess it means passing a loop over something and back through itself the way you attach a luggage tag…?
If so, that’s a knot (larks head) …regardless I don’t see anything in the video that shows that or any other fixing/locking action actually being performed.
Clarification would be appreciated.
In the first shot on the parked trimaran. The soft shackle knot is pulled and you see the eye in the lashing that the soft shackle is luggage tagged through. That holds the tension (jams the cascade). The video only shows the system, not the actual activity of tensioning the shrouds and applying the luggage tag to the tightened cascade. Luggage tagging is exactly how you describe, the soft shackle is just a big knot with a loop of line, that loop is passed through the eye of the lashing line and passed over the big knot and drawn tight–thereby jamming the cascade.