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Does anyone have experience with this boat? I'm interested in the folding system. It uses Farrier-like struts and sea stays. With the sea stays, the struts don't take the sailing loads, just hold the ama's up when the mast is down. There is no secondary link to control folding like the Farrier system has. How does this boat fold? 

 I'm sketching a folding tri and have been all over the map on folding systems. The Farrier system is absolutely brilliant (and patented), but the secondary link needed to control folding (3'rd image) is not great for a one-off boat. I'd also prefer sea stays to lighten the loads on the beams. Can anyone shed light on the Radikal?

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No answers to your questions but AFAIK Farrier's patent's run out ages ago as he acknowledged (he was always surprised people hadn't copied it)

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Watching the development and refinement of the F-22, seems to me it would be very hard to beat that system.  I guess i get the advantage of waterstays but if I was on the boat, the first time i saw the waterstays dragging through the water would really bum me out.  Waaaaaa

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You really do need that second set of folding struts to control the folding otherwise the boat will wobble everywhere like jelly if you try to fold or unfold on the water. I’m guessing that the tri in your photos would only be able to fold/unfold on the trailer. When I designed and built a 9mtr trailerable tri years ago I didn’t realise the difficulty and complications involved in Ian’s system which I used on it (Lukim Yu). I have great respect for his ingenuity in designing this system.

    It ended up working well on Lukim Yu after much head scratching and procrastinating but I didn’t have total confidence in my homemade struts so decided to also fit waterstays fore and aft. (I always wondered if they were needed but glad I did as Lukim Yu is still racing more than 20 years on). 
    The waterstays did tend to catch waves when it was rough so in hindsight I would have tried to get them as high as possible.      

0142E5C9-F9D2-4F35-B92C-A70BD88FA647.png

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Ian's patent seems to be US 5031557, filed in 1989, which means the invention became public domain in 2009.  There are also quite a few other patented trimaran folding systems in the patent data base you might look at.  Go to USPTO.gov, patent search.  You could start with 5904111 (Frigard), look at the patents it references, and is referenced by and spread out from there.  You could also search for the term trimaran in the field TITLE, but that by itself won't show that much.  But the trick is to find a starting point and follow the tree of referenced and referenced by patents.  Looking at patents is useful because if the patent document does not teach the invention clearly enough to be used by someone else it is invalid.   Don't feel bad about looking at patents either:  the basic deal with a patent is that you get 20 years of protection and, in return, you teach everyone how to do it once the 20 years is up. Go to uspto.gov, click on:  patents, search for patents, Full text and image data base, quick search.  Read the text, and then if it looks close, pull up the images.  The images and the description of the images is where the good stuff is, but they are slow to pull up.  Let me know if you have any questions.  For an engineer, this can be a very valuable tool.

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3 hours ago, he b gb said:

You really do need that second set of folding struts to control the folding otherwise the boat will wobble everywhere like jelly if you try to fold or unfold on the water. I’m guessing that the tri in your photos would only be able to fold/unfold on the trailer. When I designed and built a 9mtr trailerable tri years ago I didn’t realise the difficulty and complications involved in Ian’s system which I used on it (Lukim Yu). I have great respect for his ingenuity in designing this system.

    It ended up working well on Lukim Yu after much head scratching and procrastinating but I didn’t have total confidence in my homemade struts so decided to also fit waterstays fore and aft. (I always wondered if they were needed but glad I did as Lukim Yu is still racing more than 20 years on). 
    The waterstays did tend to catch waves when it was rough so in hindsight I would have tried to get them as high as possible.      

0142E5C9-F9D2-4F35-B92C-A70BD88FA647.png

What a beautiful tri, He b gb. More photos? Thanks everyone for the comments.

The boat I've been sketching has fairly high freeboard so good angles on the water stays and unlikely to drag. I've had some ideas about how to control the folding, but really want to learn about the Radikal tri folding system. I've made a bunch of models to try to get my head around the secondary link, but there seems to be no way to do it without 4 big molded recesses notching way into the hull. The metal parts count for the farrier system is huge and the loads on the beams are higher than if using water stays. I sailed a lot an a 35' Walter Green tri and it had water stays and very lightly built ply and timber crossarms. Very rigid in a blow.

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Its much the same as the Seacart 26, where you are reliant on keeping one Ama fully  extended whilst mooring on the water. To be fair the F series of boats are on the verge of capsize in any sort of wind with the Ama's folded.

image.png.e181a506d8d6416ff946a22b825d50a4.png

You are totaly reliant on the mast taking the loading of the Ama as its folding via the front stay, you just need to tighten it as you go. It works, we designed the TC600 this way to ensure lightness, but in trials at home off the water everything was reliant on the mast staying up. As soon as the mast was down for any reason you needed trailer supports for the Ama's which is OK but there was always the what if a mast did come down whilst at sea. We had a small bar running parallel with the beam just behind and set in length so that the Ama's didn't fold aka Farrier but instead did a sort of half fold ending with the beam end sitting on the top of the roof of the cabin and the Ama still relatively vertical to prevent sea growth on the sides of the Ama when anchored. We had to do it this way as the TC600 has a very dinghy like shape on the undersides and it would be totally unstable unless at least 1 Ama is fully out or two half folded. 

 

image.png.078a5743dc8a78ad6e8ba31d2ccd110c.png

 

 

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Interesting that the Seacart 26 uses struts at all. They let it fold, but it can't be folded out without the mast up. The system I'm interested in is more like the Radikal, where the struts would hold the boat rigid without the mast up. 

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Thats not quite so, the struts are long enough that when the beams are fully vertical, the strut pushes the Ama up and effectively holds the Ama up in the air enough to put the boat on a trailer.

However as we deduced at sea thats a different matter and it would seem Radical have gone to a half way house where by lowering the hull connection, there is some triangulation enough to hold the beam in place. That I would suspect be not enough to withstand sailing loadings because of the short lever arms but together with the water stay is light and simple. But to lower the hull connection you have to have enough vertical section on the hull to be able to lower the connection and fold the strut vertically.

Here is the Seacart version on my Tri folded.

image.png.77d7caa80d822fbe0a412c5ba06ff24b.png

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Just as a quick aside, its dirty and less aesthetic but you can also put a compression bar from the mid section of the beam to the top of the cabin roof to create a triangle sufficiently strong to have a similar effect to the Radical idea.

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4 hours ago, Waynemarlow said:

To be fair the F series of boats are on the verge of capsize in any sort of wind with the Ama's folded.

We had to do it this way as the TC600 has a very dinghy like shape on the undersides and it would be totally unstable unless at least 1 Ama is fully out or two half folded. 

True for F242, but it was quick to get a float out.... but my SeaRail is too unstable to motor while folded.  I stabilize searail by tying a limiting line from the shroud eye on the float and cleating on the main hull (both sides) so the floats can't go all the way out, tie a line between the two rear beams and pull down with the mainsheet to the limiting line length, then finally tightening the shrouds (used halyards to stabilize mast while shrouds are loose).  Can't do it underway, though.  so parking in a slip requires me to park someplace else, first.   Fortunately, the marina I stay at usually has a side tie available.  

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18 hours ago, Russell Brown said:

I've made a bunch of models to try to get my head around the secondary link, but there seems to be no way to do it without 4 big molded recesses notching way into the hull.

Would this do?  Blue is unfolded, orange is folded, the fat lines are the struts of the folding system (and the dolphin striker on the waterstay).

I haven't checked what that would do to shrouds.  You'd have to adjust the geometry to take care of that once you know how high up the shrouds attach.

Trimaran folding.jpg

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Hi Russ,   Not what you asked but I wondered if you've given thought to an ama collision.  Ian has a fix page for that using what he calls diagonal braces, but sometimes they are called water stays.  Something to think about if you haven't already.  Link

Screen Shot 2021-08-12 at 5.06.09 PM.png

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21 hours ago, Russell Brown said:

What a beautiful tri, He b gb. More photos? Thanks everyone for the comments.

The boat I've been sketching has fairly high freeboard so good angles on the water stays and unlikely to drag. I've had some ideas about how to control the folding, but really want to learn about the Radikal tri folding system. I've made a bunch of models to try to get my head around the secondary link, but there seems to be no way to do it without 4 big molded recesses notching way into the hull. The metal parts count for the farrier system is huge and the loads on the beams are higher than if using water stays. I sailed a lot an a 35' Walter Green tri and it had water stays and very lightly built ply and timber crossarms. Very rigid in a blow.

have a look here  ....  https://yachthub.com/list/yachts-for-sale/used/sailing-trimaran/trimaran-nusa-tiga-9m/255654

Nothing to do with me, but have raced against her and she is quick

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23 hours ago, Waynemarlow said:

Its much the same as the Seacart 26, where you are reliant on keeping one Ama fully  extended whilst mooring on the water. To be fair the F series of boats are on the verge of capsize in any sort of wind with the Ama's folded.

image.png.e181a506d8d6416ff946a22b825d50a4.png

You are totaly reliant on the mast taking the loading of the Ama as its folding via the front stay, you just need to tighten it as you go. It works, we designed the TC600 this way to ensure lightness, but in trials at home off the water everything was reliant on the mast staying up. As soon as the mast was down for any reason you needed trailer supports for the Ama's which is OK but there was always the what if a mast did come down whilst at sea. We had a small bar running parallel with the beam just behind and set in length so that the Ama's didn't fold aka Farrier but instead did a sort of half fold ending with the beam end sitting on the top of the roof of the cabin and the Ama still relatively vertical to prevent sea growth on the sides of the Ama when anchored. We had to do it this way as the TC600 has a very dinghy like shape on the undersides and it would be totally unstable unless at least 1 Ama is fully out or two half folded. 

 

image.png.078a5743dc8a78ad6e8ba31d2ccd110c.png

 

Phew, you wouldn’t want a boat wake arriving when folded like this. That’s a huge lever force acting against the cabin top happening there!

 

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10 minutes ago, he b gb said:

Phew, you wouldn’t want a boat wake arriving when folded like this. That’s a huge lever force acting against the cabin top happening there!

Theres a very strong ring beam with about a zillion layers of carbon just below that point

image.png.5ac656792777e5e396c2503133c8ce45.png

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I’m not saying that it would necessarily break things but there sure would be a lot of banging around happening. A Grainger tri called Trilogy was launched  (around the same time as Lukim Yu ) which had the single strut folding method. It was never folded on the water.

 

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Agree and the folding side of things has effectively stopped the build, every avenue seemed to end up with a downside somewhere to the point that I would change tack and end up down yet another path which on the water looked great but as soon as you want to trailer it ( which we did ) we found yet another snag, such as the rounded hull lines meant that the boat wouldn't sit in the hull cradles whilst raising the mast, instead wanting to rotate which meant we had to have the Ama's out which depended on the mast being up.

Ians system although heavy is really where I have got to as being the last thing to try. Pontoon moorings are important to most people and the ease which they can go sailing, here in the Euro region they come expensive if you can't fold.

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Wayne, I have been following your build with interest over the years and have wondered why it seemed to come to a standstill. It looks like a cool design as are all of Tims’ designs. Hope you get on the water in the not too distant future!

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15 hours ago, WetSnail said:

Would this do?  Blue is unfolded, orange is folded, the fat lines are the struts of the folding system (and the dolphin striker on the waterstay).

I haven't checked what that would do to shrouds.  You'd have to adjust the geometry to take care of that once you know how high up the shrouds attach.

Trimaran folding.jpg

I wouldn't have thought of this. I don't think it will work on my configuration which doesn't have deep vertical sides.

This topic reminds me of pedal drive systems for boats, which are a deep rabbit hole to go down.

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Another question I have is if anyone has had negative experience with a main hull that flares out above the waterline? I was sketching something a bit more extreme than the Radikal tri, but getting a bit worried about it throwing water to windward and up.  I used flare on the little Humdinger tri and don't remember it throwing water out, but it was much less flare. Any thoughts?

DSC01080 (1).jpeg

hanging.jpeg

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Russell, I had a tri plane windsurfer hull that actually had a chine that curved down at the very outside and it was very fast and dry.  If you deflect the side flow down by the time the wind catches the spray it can't climb up the hull.  I also did some edge surf boards with Tom Moreys' suggestion of silicon bead deflector edges, shaped with ice cubes that worked great.  Good luck, Guerdon.

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Sounds like a fun project Russ! 

There's a Supercat 20 tall rig that I was thinking about building a center hull for, but I figured the L7 sliding beams would be easier for a mere mortal to build. I like the updated version of the Sardine run trimaran with sliding beams. 

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When I built the F-32, I got 4 people round to help me fold it up for the first time. The thing almost folded itself! Very clever design

 

Still can't figure out what is going on........

 

 

 

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Attention Russell;

There are some photos here https://www.facebook.com/tomh151/media_set?set=a.1402421996720242.1073741831.100008573640993&type=3

of John Pattersons 21 foot tri, it uses a system that segments the beam, not a winner for my money but food for thought.

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I agree about the folding system, but that boat is just super cool. You found more photo's than I had seen before. it's hard to make a high-volume boat look good, but that one does. 

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On 8/13/2021 at 2:36 PM, Russell Brown said:

I wouldn't have thought of this. I don't think it will work on my configuration which doesn't have deep vertical sides.

You may be able to adjust for your needs.  I defined the lower point on the hull, and two on the beam.  I drew a circle around the lower point to define where the outer point on the beam, and the strut between them, would end up after folding.  Because you wanted waterstays, I thought I could attach the strut to a dolphin striker on a waterstay, which gave me a bit more freedom in where the outer and lower strut could go, and how long it had to be.  I rotated and shifted until the whole thing was reasonably narrow.  Then I looked at the two points on the beam, drew the perpendicular bisector between them, and where that intersected with the hull, that was where the inner strut needed to attach.  If that didn't give me something that looked right, I adjusted the points on the beam, and tried again.  It took only a few iterations.

I note that Farrier's system does not require the struts to cross over each other.  Mine does, and I don't know whether the whole structure might go a bit wobbly in that range.

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On 8/13/2021 at 6:48 PM, guerdon said:

 If you deflect the side flow down by the time the wind catches the spray it can't climb up the hull.

I agree with this idea. Really acute sharp chine edges help too, even if only horizontal.

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On 8/13/2021 at 6:16 AM, Russell Brown said:

I was sketching something a bit more extreme than the Radikal tri, but getting a bit worried about it throwing water to windward and up.

One thing i noticed on F-boats is that if the spray doesn't mqke it in front of the fwd beam it tends not to come up through the nets. Guessing it's because the airflow is mostly directed horizontally under the nets.

The only spray that hits you is the one that comes off the rapidly increasing flare just in front of the Fwd beam or any heavy one that finds the gap before the net right behind the beam.

Going downwind but plowing through waves coming the other way shows the spray pattern (although there isn't much on the windward side): https://m.facebook.com/Teampestou/videos/reaching-towards-hornby-plowing-through-the-remaining-se-swelldesolation300/1018360495660530/?__tn__=-R

Either don't start the flare until aft of the beam or make sure you have a sharp ideally downward pointing chine in that area.

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On 8/16/2021 at 6:42 AM, JanetC Gougeon32 said:

Sounds like a fun project Russ! 

There's a Supercat 20 tall rig that I was thinking about building a center hull for, but I figured the L7 sliding beams would be easier for a mere mortal to build. I like the updated version of the Sardine run trimaran with sliding beams. 

Our L7 beams slide very easily, out of water or in.  They do wobble a bit when deployed. Clunk clunk. But I think that could be worked around (rubber door stops?). Depending on the hull heights, you might have trampolines in the water when folded.  Other than that, clean and intuitive.  
 

As an aside, keep the raising shroud bases the same level as the mast step, without a center hull cabin if you can.  It will make mast raising a lot simpler, especially if you do it a lot.  Try a model.  

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1 hour ago, Zonker said:

You'll need something harder than rubber door stops. Solid hardwood.

Engine mounts?  

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3 hours ago, Amati said:

As an aside, keep the raising shroud bases the same level as the mast step, without a center hull cabin if you can.  It will make mast raising a lot simpler, especially if you do it a lot.  Try a model.  

Another method is to use temporary solid raising shrouds which attach to a sliding slug in the mast slot. Lateral stability of the mast is provided during raising and lowering without the base of the shrouds being precisely aligned with the mast base. It works.

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21 minutes ago, cyclone said:

Another method is to use temporary solid raising shrouds which attach to a sliding slug in the mast slot. Lateral stability of the mast is provided during raising and lowering without the base of the shrouds being precisely aligned with the mast base. It works.

I’ve done that & it works really well, along with a mast crutch with a 5’ sliding mast raiser within, but the question becomes where do you keep all that stuff?  Along with the gin pole, line etc etc.  

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20 minutes ago, Amati said:

but the question becomes where do you keep all that stuff?  Along with the gin pole, line etc etc.  

Fortunately in my case it all goes back into the barn. I agree that it is not the most convenient or elegant system for a boat that is trailer sailed but for twice a season it’s fine with me.

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Russell, we just splashed the min-ton and raised the mast on the trailer.  The shrouds were not on the same axis as the pivot point [the G32 was easy] however by using a ladder in the aft cockpit to start the vertical tilt@30 degrees.  The breakthrough was in using carabiners on the side stabilizers that slid as the mast went up we did it.  It scared my family because the mast was so tall@40'+the trailer height.  Me the lofty dreamer,[I was stoked to see that it could be done].  Let me know if you want more info.  Aloha, Guerdon.

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6 hours ago, Airwick said:

One thing i noticed on F-boats is that if the spray doesn't mqke it in front of the fwd beam it tends not to come up through the nets. Guessing it's because the airflow is mostly directed horizontally under the nets.

The only spray that hits you is the one that comes off the rapidly increasing flare just in front of the Fwd beam or any heavy one that finds the gap before the net right behind the beam.

Going downwind but plowing through waves coming the other way shows the spray pattern (although there isn't much on the windward side): https://m.facebook.com/Teampestou/videos/reaching-towards-hornby-plowing-through-the-remaining-se-swelldesolation300/1018360495660530/?__tn__=-R

Either don't start the flare until aft of the beam or make sure you have a sharp ideally downward pointing chine in that area.

I'm not sure I have a choice but to have the hull flare out above the waterline because I need volume inside. The flare isn't very pronounced ahead of the front beam but it's only around 10" above the waterline. The freeboard is higher than a Farrier. Still only sketches until I get past the folding system. Back to swing wing sketches.

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1 hour ago, guerdon said:

Russell, we just splashed the min-ton and raised the mast on the trailer.  The shrouds were not on the same axis as the pivot point [the G32 was easy] however by using a ladder in the aft cockpit to start the vertical tilt@30 degrees.  The breakthrough was in using carabiners on the side stabilizers that slid as the mast went up we did it.  It scared my family because the mast was so tall@40'+the trailer height.  Me the lofty dreamer,[I was stoked to see that it could be done].  Let me know if you want more info.  Aloha, Guerdon.

String bridles for temporary shroud attachments work too.

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7 hours ago, Amati said:

I’ve done that & it works really well, along with a mast crutch with a 5’ sliding mast raiser within, but the question becomes where do you keep all that stuff?  Along with the gin pole, line etc etc.  

with the trailer

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1 hour ago, teamvmg said:

with the trailer

Which is fine until someone waltzes off with the blocks, or you build a box on the trailer for all the stuff, drive through a big rainstorm and discover it wasn’t rain resistant :P enough.  But wait, there’s more….

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6 hours ago, Russell Brown said:

String bridles for temporary shroud attachments work too.

Suffered through that- if you don’t use them enough to remember what goes where, untangling the damn things every time you use them, putting them away where you can find them……… it gets old, tiring, frustrating, and tedious fast.  But then I look at the Broads Boats lowering rigs to get under small bridges while racing, and then raising them again immediately, so it’s possible to streamline the process.  Most I’ve seen raising masts do get frustrated and just grab the mast and muscle it up to get it over with, which ends up with a wrenched back or torn or pulled muscles, and then you’re supposed to go sailing? :lol:   Roger Martin’s mast raising system on the Presto 30 wasn't bad, and not too fiddly, (I suppose you could use a boom)  but those are unstayed masts.  So I went with a folding Gunter on the L7 ( as opposed to a sliding Gunter), but it still needs 2 people to raise the bottom mast.  And my wife is not too thrilled about that,  but with carbon spars, at least it’s lighter, with smaller sticks.  It’ll get there, I think, but with COVID, spending a lot of time down at the dock surrounded by the inquisitive friendly well meaning unmasked turns medium sized stuff into things you have think twice or three times about before just doing.  It’s like having a boat on Mars- you have to mask up before going out to do something. .  Add to that supply chain problems getting or making bespoke parts, or getting creative with lashing (and testing said lashings :wacko:) it takes a lot of time.  And I really don’t want to become a professional rigger/builder- sometimes I just want to go for a sail, come back home and play my cello.  Sorry for the rant.  It just seems like there’s room for some design and process simplification / development here, and Jan & Meade are gone.  :(

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9 hours ago, cyclone said:

Fortunately in my case it all goes back into the barn. I agree that it is not the most convenient or elegant system for a boat that is trailer sailed but for twice a season it’s fine with me.

I knew the new shed should have been twice as big…..:rolleyes:

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8 hours ago, Amati said:

Suffered through that- if you don’t use them enough to remember what goes where, untangling the damn things every time you use them, putting them away where you can find them……… it gets old, tiring, frustrating, and tedious fast.  But then I look at the Broads Boats lowering rigs to get under small bridges while racing, and then raising them again immediately, so it’s possible to streamline the process.  Most I’ve seen raising masts do get frustrated and just grab the mast and muscle it up to get it over with, which ends up with a wrenched back or torn or pulled muscles, and then you’re supposed to go sailing? :lol:   Roger Martin’s mast raising system on the Presto 30 wasn't bad, and not too fiddly, (I suppose you could use a boom)  but those are unstayed masts.  So I went with a folding Gunter on the L7 ( as opposed to a sliding Gunter), but it still needs 2 people to raise the bottom mast.  And my wife is not too thrilled about that,  but with carbon spars, at least it’s lighter, with smaller sticks.  It’ll get there, I think, but with COVID, spending a lot of time down at the dock surrounded by the inquisitive friendly well meaning unmasked turns medium sized stuff into things you have think twice or three times about before just doing.  It’s like having a boat on Mars- you have to mask up before going out to do something. .  Add to that supply chain problems getting or making bespoke parts, or getting creative with lashing (and testing said lashings :wacko:) it takes a lot of time.  And I really don’t want to become a professional rigger/builder- sometimes I just want to go for a sail, come back home and play my cello.  Sorry for the rant.  It just seems like there’s room for some design and process simplification / development here, and Jan & Meade are gone.  :(

Mast raising and lowering doesn't get much easier than a G32.  The boom is the gin pole, and the main sheet pulls the mast up. 

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Amati, if I played the cello, my world would be complete.  Since I don't, I have to sail upwind or surf to get that moaning power sensation.  

Every body wants to go to heaven, but no body wants to die.

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On 8/12/2021 at 4:46 AM, Waynemarlow said:

Just as a quick aside, its dirty and less aesthetic but you can also put a compression bar from the mid section of the beam to the top of the cabin roof to create a triangle sufficiently strong to have a similar effect to the Radical idea.

Is this angle oblique enough for effectiveness?

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2 hours ago, guerdon said:

Amati, if I played the cello, my world would be complete.  Since I don't, I have to sail upwind or surf to get that moaning power sensation.  

Every body wants to go to heaven, but no body wants to die.

Frankly, riding a Triumph Bonneville 750 is damn close.  (Or a Newport Finn with Bruder Mast) Cello playing is a lot like golf. Moments of glory, hours of agony.  ‘Nuff said.

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On 8/12/2021 at 12:22 PM, Russell Brown said:

What a beautiful tri, He b gb. More photos? Thanks everyone for the comments.

The boat I've been sketching has fairly high freeboard so good angles on the water stays and unlikely to drag. I've had some ideas about how to control the folding, but really want to learn about the Radikal tri folding system. I've made a bunch of models to try to get my head around the secondary link, but there seems to be no way to do it without 4 big molded recesses notching way into the hull. The metal parts count for the farrier system is huge and the loads on the beams are higher than if using water stays. I sailed a lot an a 35' Walter Green tri and it had water stays and very lightly built ply and timber crossarms. Very rigid in a blow.

Thanks Russell, here’s a couple of photos of Lukim Yu off the net. I’ve got a few of my own shots stored away in boxes as we have recently moved home, I’ll post a few when I find them. You can see the home made struts in the first of these photos. For the folding geometry I made 10/1 scale 2 dimensional models and tweaked the strut lengths and pivot points until the hulls nested. Because Lukim is about half a meter wider than the Farriers we had to winch the last few feet of the floats together when folding on the water as it was actually lifting the main hull a few inches, this was quite easy to do not requiring much winch power. Cheers,Gerald.

17024069-56D2-497E-BD0F-D24688931363.png

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"But then I look at the Broads Boats lowering rigs to get under small bridges while racing, and then raising them again immediately, so it’s possible to streamline the process."

Some Broads boats at least use a pivot point a few feet up the mast where the pivot axis keeps the mast on a fore-and-aft line, and a very heavy weight at the base of the mast to counterbalance it so it's easy to pull the mast up. Fine on a mono where ballast can be useful; not such a good idea on a multi :(

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 Amati, my dad didn't let me near motorcycles[knew I would die] but I did learn to sail on a Finn in the winter[broke three masts].  We are blessed with every breath of wind, and every moan of the cello.

 

 

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4 hours ago, he b gb said:

Thanks Russell, here’s a couple of photos of Lukim Yu off the net. I’ve got a few of my own shots stored away in boxes as we have recently moved home, I’ll post a few when I find them. You can see the home made struts in the first of these photos. For the folding geometry I made 10/1 scale 2 dimensional models and tweaked the strut lengths and pivot points until the hulls nested. Because Lukim is about half a meter wider than the Farriers we had to winch the last few feet of the floats together when folding on the water as it was actually lifting the main hull a few inches, this was quite easy to do not requiring much winch power. Cheers,Gerald.

Hi Gerald, Thanks for the photos. Still very attracted to this system; using the struts for folding and for holdng the beams up when the mast is down, but using water stays for the loads.  I'm not sure how you got the secondary link to work. All my modeling shows the inboard end needing to be way below deck level as the Farriers are. I'm thinking about not using the secondary links, but using a tube running fore & aft between struts to control bow up or down wobbles when folding. John Marples did this with a 26 footer. I'd still need the mast to be up for folding on the trailer and it would take some figuring out for sure.

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1 hour ago, Russell Brown said:

John Marples did this with a 26 footer. I'd still need the mast to be up for folding on the trailer and it would take some figuring out for sure.

John’s Constant Camber 23 uses the fore & aft torsion tube as well but the simple folding method although very sturdy when unfolded is not self supporting and requires an additional dolly and a jacking ramp with the boat still on the trailer. It also takes two people.Folding is only done with the mast down.

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On 8/20/2021 at 1:55 PM, Airwick said:

The only spray that hits you is the one that comes off the rapidly increasing flare just in front of the Fwd beam or any heavy one that finds the gap before the net right behind the beam.

Maybe I am not reading this right, but, my experience on F27s and F28s is that one can be totally douched in the cockpit from chop hitting the rear beam whilst reaching at speed in high winds and moderate seas.  We always have to close up the companionway to keep the interior from getting damp.

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Not sure how they do it, but Astus 20.5 is sliding tube design (arguably much simpler and lighter than folding).   Granted the slop in the tubes will likely be offputting but a little extra shroud tension might well alleviate that venal sin.  Makes for a really stable ride motoring to dock in a slip.  https://www.youtube.com/watch?v=pYTD2IqYMME

 

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Don’t you think sliding tubes would be more practical and reliable in carbon ?

Stiffer and more thermally stable. 
$$$$ of course but simpler and lighter. 

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The problem with sliding tubes is they really screw up the cabin space big time particularly if you are trying to maximise the space on a small boat.

The more I look at the Radical 1/2 way house, that of Farrier style arms controlling the folding and water stays to assist with the sailing loads, the more I think it’s really the only practical and lightweight solution.

As we discovered with light weight boats, do not attempt to raise / lower the mast without having the stability of at least one AMA out.  No matter how we tried to tie the boat down on the trailer, even the slightest side wind was enough to make the process fraught with things going wrong. We started with an older all Carbon mast which was OK but as soon as we went with the design brief of using entirely an F18 as a donor boat ( the earlier F18 masts are pretty stout and heavy ), the mast raising forces just seemed to over power the 120kgs centre hull and made it sort of squirm and move about on the trailer let alone on the water. There was just too much of a wing and prayer every time we raised and lowered the mast with the Amas in that we halted the project for a rethink.

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