Tri with staggered beams ama slide in system...

[Angélique]

I posted the below quote as a suggestion here, but now it's distracting from the topic there, so here's a split off thread, further reactions on the "staggered beams ama slide in system" please here . . .

Maybe the below beam slide system is an idea for a slightly updated version of the Buc 24 or the 28 . . ? ? ?

Saw this Astus 24 ^{(sort of translation)} where the port and starboard beams are just next to each other and can slide along each other to slide the amas in for berthing and trailering.... (see videos in the original link)

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P.S. - I don't know how I should interpret this shot on the beams, maybe bias by a wide-angle lens . .

Kurt Hughes has a few designs with staggered beams like that, it's a smart way to go!

Barry

Improvments?

The "problem" with using sliders for the Bucs, is basic- Bucs are all too wide. A 24 is 19' beam so the "half" beams are too wide to be legal to trailer, or they have to be very heavy to take the cantilever loads. I am not saying it couldn't work, but the engineering and construction would be a lot more complex than a basic Buc.
B

Not sailed it, but been on it and I found the width of these Beams in the middle of the cockpit quite annoying.

Yeah your right! 4+4=8 add sleeves and containment and you just lost a foot of boat, twice!

Barry

Start an Astus thread

Done !

 

[Marmoset]

ok! and going deeper ill say look at kurt hughes daysailer 23. yes plans tad more than free or cheaper ones out there but! would buy itself back in build cause it has beach cat amas as an option. and not sure but slide in beams look under over instead of side by side, which would save space, if not its somehow single tube slide in.

barry

 

[warwick]

This is a video clip of the Autus 24 at a boat show

https://www.youtube.com/watch?v=5kGkUe0otFM



one being slide apart.

https://www.youtube.com/watch?v=k-ETBkE_m6I

 

[lucdekeyser]

It is rumored that Astus uses Teflon rings in the tubes to ease the sliding. Reports about the very first Astus boats (without Teflon rings?) mention the use of lots of salad oil. I could not find any reports about sliding problems on the french forums. What is your opinion? How easy would it be to clean the insides when sliding gets difficult or the tubes get stuck?

 

[warwick]

To me i see each beam reduction approach having their own limitations in overall beam.

I wonder if it would be possible to use strips of teflon tape length wise.

 

[Angélique]

ok! and going deeper ill say look at kurt hughes daysailer 23. yes plans tad more than free or cheaper ones out there but! would buy itself back in build cause it has beach cat amas as an option. and not sure but slide in beams look under over instead of side by side, which would save space, if not its somehow single tube slide in.

barry

Thanks for the tip Barry, from the drawing at the bottom of the quote it looks like you say, slide in beams staggered under and over each other...

Kurt Hughes: 23' Daysailor Trimaran

It can be built to get narrow rapidly with the sliding-tube Mono-slip connectives option.​

I don't understand this part though . . ‘‘ Mono-slip connectives option. ’’ . . what does that mean . . .

 

[Angélique]

This is a video clip of the Autus 24 at a boat show

https://www.youtube.com/watch?v=5kGkUe0otFM

From the video at 5:19 high seats or short legs . . ? ?

 

[Marmoset]

somehow suggesting central tube house both? which i could see in square beams but aero shape? But it is a nice boat, specially taking into account couple hundred bucks for beach cat and amas are done!

Barry

 

[Jetboy]

I'm using a a sliding mechanism for a new trimaran I'm building. The tubes are both aluminum and have .026 inches of clearance. I found one spot in one of the tubes that does not telescope well, but I have removed it - fortunately it was near the end and I didn't need it.

The size that fits is 4" schedule 40 pipe outside of 4" OD tube. The 4" nominal sch. 40 pipe is 4.026 ID and 4.5" OD. And both are common enough I can buy them off the shelf at my local supplier for about $100USD per 20' section. My system is unstayed and will use outer tube sections that are removed for transportation, but when inserted, to all the way to the boat's center line, and are 8' long. This is an 18' trimaran with 16' beam. If I find it too flexy, I'll go ahead and add some water stays. The internal structure is easy to work with in that respect as I kept access to the areas I would need to add some reinforcement for the water stay tangs. It's possible that I may just build them in now just in case.

the limitation of the Astus mechanism is of course the width max. it is a very nice system for small trimarans and I could have done it with mine. With my system it becomes modular - I can make it as wide as I want. I can have multiple float sets (I already have 3 sets of floats I'll be experimenting with) - so I can put lifting foils in one set, have a high volume set, or whatever I want to change out there at the float. There's a lot of advantages for a tinkerer lime myself to having the floats be modular and easily removable.

The other most important aspect is that for winter storage, I can pull the floats off easily, stack on top, and put the boat sideways in front of my cars and it all fits in my garage. This a concern specific to me and my situation, but it works for me.

With respect to sliding, I've found that as long as the tubes remain clean, they telescope very nicely with just a little bit of lubrication. I use vaseline - mostly because I keep a tub of it on my welder for use welding and it was handy.

I think for final assembly I'll use a different lubricant. Not sure what yet, but something that won't collect dust is going to be a big necessity. Maybe just graphite powder?

 

[warwick]

thanks for your practical input jetboy.

 

[tspeer]

...
I don't understand this part though . . ‘‘ Mono-slip connectives option. ’’ . . what does that mean . . .

It means the beams can be shortened so the trimaran can fit into a slip sized for monohull boats. It's an optional feature, compared to the simpler approach of fixed beams that can't be shortened on the water.

 

[Angélique]

Thanks Tom

I was thinking it had to do with the sliding system itself, that's why I didn't understand it.

 

[Marmoset]

so mono collective isn't referring to the beam cartridge itself? sometimes i over think things! haha


Barry

 

[mundt]

https://www.youtube.com/watch?v=UQSasSXnrTU

 

[mundt]

above youtube video depicts tri with sliding beams, offset fore and aft, I-beams made of g-10. Well-proven strength and function.