Erutan,
| I mentally have a tough time contemplating telescoping beams because of my experiences with my current trailer.If I may, that's metal on metal, right? Much higher friction coefficient, I think, than slippery plastics and the right lube.
You're right for the most part, but there are also rollers involved. It works a lot better when the boat isn't on the expanding/contracting trailer. The boat would be largely unloaded, so less force on the mechanism, though I imagine that the mast(s) would want to sway back and forth.
UHMW PE on UHMW PE should be fine in terms of smoothness. I wouldn't want any lubrication other than SailKote or another dry lubricant.
The trick would still be in keeping things parallel. With enough bury it might not be a problem.
I am not sure an expensive, heavy, super cool, marine screw is the best fix.. But I can see a thing to tighten is needed. But perhaps coolness trumps all.
Lashings like the Wharrams are probably the simplest, lowest-tech, cheapest, and least failure-prone option.
But after that, I still like the screw. Huge threads so you never have to worry about cross-threading it or getting it jammed with a touch of salt and grit. Lots of metal so there's little worry about with stress fractures or crevice corrosion.
For the folding mechanism on the Ex40 and Air 40, you'd only need one screw per beam assuming the hinges are snug. Carry four and you've got two spares.
(Though to argue against myself, four screws in a telescoping or sliding arrangement would be rock solid assuming the ends are bonded to the ulls)
And I think you loose interior to the swing, perhaps?
I think the loss of space in the hull on the Mark 1 version of the Ex40 was due to putting the masts through the beam ends to tie all the sailing loads and structures together into one super-solid whole. You could probably keep everything outside, but that said, I'm not sure that the internal space outside the beams and masts is useful in a hull that size.
Speaking of which, Rob and Steinar's take on the Mark 1 folding version is really growing on me. It's simpler than cat2fold and it allows for a shorter folded LOA.
Which actually makes me re-think the tender. It's a really elegant design, but most years I probably wouldn't use the tender for anything other than driving the boat. In which case, building that outboard well in the lw hull would probably end up being a less costly and simpler solution. In which case I could go with folding instead of telescoping.
I suppose at this point I could be lightly nudged to one side or the other by another stroke of design ingenuity.
Water?
Not for me. Each hull can have its own tank. Heads will be compositing, so no water or plumbing needed there. Just a small tank for washing hands in the lw hull, if there is indeed a head in there.
I was guessing there was no way to have tender clearance under the ww hull. But perhaps that guess is off? Or we make it so.
There's probably not enough width for a standard 8.5' width trailerable, but if we don't mind pushing out to 10' to 12', there's probably enough between the hulls for a tender with 5' of beam. The trick would be as you point out -- clearing the foot well and steps down into the main ww hull. Maybe if the tender were attached only at the nose, the transom would end up being low enough to allow the rest of it to clear the footwell.
Was there not a rendering that had a rendering (AIR40?) with the tender between the hull when folded?
The Air 40 is a great design. I'd still want an Ex40 myself, but every time I look at the Air 40 I'm impressed.
I believe the renderings showed the tender to the side of the boat when folded. Though it also looks as if there's enough room between the hulls for a tender as long as it's low enough to avoid the stairs/footwell.
Nice! You know, we cannot run with scissors.
Good one. But... we might be able to reach. (sorry)
I was thinking we seem to want highest beam clearance to lee, as the ww clearance is very little/not needed?
That's what I would normally think. But if the tender is connected to the higher beam on the leeward hull, and you telescope down to collapse the boat, the tender is going to run into the cabin/deck. If the lower section is to leeward, the tender can just slide under the main hull once you drop its aft end into the water.
Where do we put the toy box and bench seats when marinaing?
On the Ex40 you could probably build the box in a way that lets you stash it between the masts, provided you weren't planning to get on and off the boat in that section.
Seats would work. Or a toybox. I'm bot sure about both. Perhaps they fit together like Russian dolls.
I'm not sure about the Air 40, with its (very nice) design of putting those seats over the leeward hull when folded.
- Mike
| > The telescoping seems able to get good structural bury and great extension very simply and lightly. Mike, et. al. Any thoughts?
| I mentally have a tough time contemplating telescoping beams because of my experiences with my current trailer.
If I may, that's metal on metal, right? Much higher friction coefficient, I think, than slippery plastics and the right lube.
| Plus the look is non-optimal.
Ha! If you keep telling me whats sexy I may end up with a sexy boat!
Seriously, keep an eye on the curves. I am almost blind to them.
| Not just the profile, but also from above -- I'd like beams that aren't parallel, as shown in a lot of the older harry's, and scissors (or the Ex40 renderings) can handle that.
Sure. But why? Just ascetics?
I was thinking spread beams give better distance between sails, but I am not sure it does matter for sails.
Now I think spread beams just makes a larger more perpendicular surface to the wind.
| That said, I'm a bit of a problem child in this area, and I have a feeling I'll be in the minority.
As a sophisticated modern man, I listen to minority views...
| The scissors are going to weigh more, plus are going to cost twice as much.
And I think you loose interior to the swing, perhaps?
| > So lets just assume tillers?
| >> Definitely. And with telescoping extensions.
| >>> Mike said this was preferred anyway, IIRC.
| It won't get simpler, less expensive, lighter, or less failure-prone than tillers, especially if you're folding on the water.
|
| There are no cables to tighten, or which might hop off a quadrant, no hydraulics to maintain or leak, and nothing to remember when you're folding (if you forget to collapse the tiller extensions, the worst thing that happens is that you then do it). And nothing to disassemble when transporting the boat or dismounting it.
|
| Perhaps two cables -- one for communications/electronics, one for power.
Water?
| I"m also quite partial to tillers for steering. I always feel like I'm sailing with tillers, but often feel like I'm driving a bus when I'm on a wheel.
Oh, neat. I totally do not get the wheel thing. I was thinking I missed something.
| > So, if Mike is a once a season guy, Arto is a cruiser, and I am the 2 hour guy. How does optimizing for me tick the other two off?
|
| I think it just enlightens us and expands our horizons of what's possible. Besides, if it works for the 2-hour guy, by definition it's going to work for someone who stays in a marina for a few days, or someone who folds/expands a few times per year.
Ya, I am thinking fast has got to be attractive. But still have no idea what the trade offs are.
| > Are there any we have not addressed? Or not addressed enough?
| I may have had a brain pause on the tender-mounted outboard motor.
|
| It's a brilliant design, but I'm not sure how it would work when the boat is collapsed/folded on the water. It's probably not a show stopper for trailering if you have a boat ramp where you can tie up for five minutes, but you'd definitely want a working motor when finding a slip in a marina.
|
| Maybe there's just enough room between the hulls when the boat is down to 12' for a narrow-ish catamaran tender with an outboard.
Neat! That solves the trailering issue too, right? I was guessing there was no way to have tender clearance under the ww hull. But perhaps that guess is off? Or we make it so.
Sliding beam on the T40? It's sliding beams all the way down!
Was there not a rendering that had a rendering (AIR40?) with the tender between the hull when folded?
| But then you'd have to detach it from its normal beam mount and reattach in the new position.
I know nothing, but, one is pretty much gonna have to drop the tender no matter what, to fold? I mean, the deck, which the tender is a big part of, is folding to nothing, and the tender is moving under the ww cabin.
| Unless you have telescoping beams, and the leeward section is the lower section (or outer section, depending upon the design), where the tender attaches.
|
| Hmm. I still want the darn scissors folding mechanism, but I probably care more about the tender/outboard than I do about the scissors.
Nice! You know, we cannot run with scissors.
| The other option I'd contemplate would be a well inside the lw hull
If that's where we get to, fine. But why carry 2 motors? And a bunch of other costs.
| But there's a lot more to be said for the simplicity of the tender/sled, as well as for having a hard tender onboard all the time (and an easy way to load/unload).
Yep yep yep.
| > Lowest beam to windward, and highest to lee?
| Probably the opposite if we want the tender to work when the boat is collapsed.
|
| Though if one side is lower, putting that side on the lw hull, which is being pushed down into the water when loaded, is a bit backwards.
I was thinking we seem to want highest beam clearance to lee, as the ww clearance is very little/not needed?
Perhaps the same mounts as the beam has for the T40 are also under/ the ww hull, for use when folded.
|
| Maybe inner/outer telescoping beams instead.
What you think Rob?
| > Can those beams get good strong bury to each hull and still let the other beam slide in that deep?
| Likely. The forces are known, and there's that big cabin/cockpit area to allow for a good amount of overlap.
|
| One a related note, I've always worried about telescoping beams creaking and working things loose over time when subjected to rough weather. I never though the joint could be tight enough for a solid total structure that resists wracking, while still being loose enough to allow the beams to expand and contract.
|
| But what if we had some of those big screw-in pins from the cat2fold mechanism that fasten using a winch handle?
|
| Would 0.5 mm clearance still allow for easy telescoping, particularly with a UHMW PE surface, and yet also be small enough to allow the system to be tightened down and solidified without damaging the structure?
|
| Maybe if the beams overlap like Rob's latest image, then it's a non-issue. The sleeves could be loose-ish, and then the pin mechanism could really pull the upper and lower sections together to make them behave as one.
It a reasonable point. Any slip joint has to have clearance to move. That clearance allows movement which will just be worked, wear, and break. A tightening/clamping system takes that clearance away, which just makes sense.
I am not sure an expensive, heavy, super cool, marine screw is the best fix.. But I can see a thing to tighten is needed. But perhaps coolness trumps all.
| But that brings us back to having the lower beam sections on the lw hull.
This lost me. Would not the screw work no matter the beam layout? What did I miss?
| I suppose I'd lean towards an inner/outer telescoping mechanism as long as it could be tightened well.
I think Rob just did a quick sketch to explain a thing. Kinda sure Tightening is a given.
I don't know if there is a up down/left right preference in Rob's mind.
My guess is, the structure naturally resists loads in a stacked layout vs inner/outer, and the wraps just limit racking or guide the movement, vs a lot of load on the wraps.
Guessing continues into the slippery tip of a lower beam riding along the bottom of an upper, might slide better than side loading and twisting forces on the wraps. But perhaps the wrap slides give much larger bearing surfaces and that, with a touch of lube, makes for smoother deployment.
We might find a specific amount of 'slop' in the wrap makes deployment easier. The idea we can easily cut them off and redo them seems great.
If we can get ~22' beam, are we thinking EX44? Or bigger?
Where do we put the toy box and bench seats when marinaing?
Posted by: Mike Crawford <mcrawf@nuomo.com>
| Reply via web post | • | Reply to sender | • | Reply to group | • | Start a new topic | • | Messages in this topic (26) |