Main beam waterstays on small foiling tri

[Doug Halsey]

It's about 19" (48cm) deck-to-bottom.

I like the look of your beam attachment as is & don't think you should go out of your way to raise it.

It's up to you of course. Just another design decision.

 

[revintage]

Thanks Doug,

A Tornado´s dolphin strut is ca 24cm from the underside of the beam, with the band attached to the beam at ca 115cm. This is 11,5 degrees.

A Nacra 18SQ has a 23,5 cm strut at 135cm: 10 degrees.

So let´s go for 10 degrees

Using a 26cm strut to get the same angle as the 18SQ DS, the waterstays will be at 23,5cm where they come out of the hull sides, if the stays are attached to the beam at 150cm. Works for me. Have added this to my previous sketch.

 

[revintage]

Have dumped the full 90x2mm main beam. Have instead ordered a 3m 110x2mm tube to acta as center of the main beam. The outer 125cm of the main beam will still be 90x2mm and telescoped inside the bigger tube with 0,5m overlap. The 110x2 has 1.85x the torsion and 1.5x the bend figures of the 90x2. Compared to a 4"x0.049" it has twice the torsion and 1.85 the bend figures.

Question is, could I dump the waterstays on this 100kg and 5.5m wide foiler build?

 

[patzefran]

Don't use Dyneema waterstays or you will need to retighten at each sailing. I have used Vectran since 2013 for my Strike 15, Strike 20 Tris and now for 2 years on the Dolphin Striker of my Paper Tiger cat, I never need to re-tighten !

 

[revintage]

Hi patzefran,

We have discussed waterstay material earlier.

To compare I put the Dyneema I use, side by side with Vectran.



BUT! The question now was whether I should dump the waterstays all together with the fatter main beam?

 

[patzefran]

To compare I have used first so called high performance Dyneema (even heat treated) which was stretching at each sailing, then I switched to vectran which since worked satisfactory ! Dyneema is never used for rigging by professional.
On the Dolphin striker of my Paper Tiger I have used 5 strands of 2 mm vectran looped thru Wichard articulated cadena bolted each side under the main beam and passing under the dolphin Striker (a 12 mm carbon rod). After two years of sailing, the mounting is as tight as new.

 

[revintage]

Hey patzefran, your answer is still a parentheses even if I appreciate your input! I will use 3x4mm Liros Static-Pro "IF" I use waterstays. We also discussed masts at some point and will now use a cut down Goodall F18 mast without spreaders together with my cut down A-cat mains. Just curious, do you live in France?

Did some more calculations and the waterstays will remain in place.

 

[patzefran]

I think it is anyway a good compromise to use waterstays. Yes I live in France near Bordeaux !
I also use a Cut down A cat main on a Shortened (8 m) A cat carbon mast on my Strike 15

 

[revintage]

Great to have the bay of Biscay as sailing area!

 

[Tallseek]

I appreciate the discussion. Embarking on a small tri builde using Apollo 16 as main hull and Hobie 16 hulls as the aka.
Taking into consolidation all you have shared.
Do you know of a thread which has already done this?
Thinking is to cut a foot off stern of both H16 ama with slant towards bow when re building. That would make both ama's right at 90 percent of the Apollo hull.

 

[revintage]

16' Apollo Vaka / 18' Prindle Ama Trimaran https://www.boatdesign.net/threads/16-apollo-vaka-18-prindle-ama-trimaran.54313/

Apollo16 is a 1.8m beam dinghy. Find another centerhull, if you want acceptable performance. I don´t consider this to be worth the effort. I could think of an old Nacra 5.5 hull as companion för the H16´s.

The Apollo16 could maybe be equipped with a pair of windsurfing boards as amas, as the boat probably has inherently good stability due to it´s rather high displacement, 1.8m beam and moderate SA.

 

[Tallseek]

Appreciate your insight to such a build.