Bolger 50' Wyoming into trimaran

"So many relations, so little railing...."

 

ASM, I have been thinking something similar to your concept for offshore cruiser that can be transported/trailered. Obviously my concept is little shorter and designed for more seas, but good sharpies with trimaran V-shaped sponsons and moderate buoyancy was my idea. It would be easily driven boat with good economical efficiency, minimalistic cruise amenities, hopefully good range, and lots of space for PV panels.
It should also provide much easier rolling motion than catamaran's snapping roll in broad chop.

ThomD, thank you for sharing the solar boat chronicle website. It is great ICW cruiser that can go offshore sustainably.

If anyone still think this is a dumb idea, please share your reasons. Bribing is what I do when I want to go offshore fishing with my buddies. But cruise? I want missus to be there, or some hot chick. How would Ostar Racer IV (or Tanton Sea-Eel) based trimaran cruise compare to Cat2fold and Seawind catamaran in terms of range per day, operational ease, efficiency, comfort at sea, cost (acquisition and maintenance)?

http://www.flickr.com/photos/hallman/tags/iv/
http://www.seawindcats.com/index.pl?page=671
http://www.cat2fold.com/

I don't want to side track this thread, but I am offering my concept to assist original thread response in positive direction.

 

Positive is highly over rated. The proposed idea of converting a perfectly good mono into a tri sucks.

If the OP wants a tri, then the aggregate of very good advice is to choose an appropriate design or get it designed by a qualified professional.

The reasons are many but 2 are safety- loss of life is a real and present risk at sea, and cost; Any 50 foot boat is going to gouge a massive hole in the wallet so why spend all that cash on a folly?

 

Good point Motorbike. A mono will be comparatively beamier then a dedicated tri's main hull, even an overly narrow mono like these Bolger box boats. It is indeed "folly" if you haphazardly morph a mono, into a 50' tri, just simply foolhardy. Again, a boat like this needs to be designed professionally, as a self designed or amalgamation of some sort, will be one costly experiment (read good guess).

 

Let's try this again.

What would be the best roll stabilizer for Bolger sharpies (Wyoming 50 or Ostar Racer IV)? Dual fin stabilizers attached to hull underwater, diving/plate stabilizers attached to swinging outriggers, buoyant sponsons on folding outriggers or gyroscopic roll damping system?

Impotant factors of good stabilizer for me would be reliability, performance, minimal maintenance and economy for a transportable boat. I would prefer any fringe benefit from this stabilizer such as additional space gain for recreation or solar panel installation. What would be positives and negatives for each system?

 

A small stabilizing sail combined with one of those anti-slapping plates Bolger and company came up with should from what I've read help keep you sorted out at anchor. I believe his Illinois uses an off-center center board for extra stability while cruising and you could put one in at the expense of some storage space beneath your galley with little problem. These would not be expensive, not out of the "motif" or increase minimum draft, and should help keep Bolger fans you encounter consistently positive.

Btw, on the centerboard, there is a fellow whose blog I came across who did something interesting: instead of swinging his board about a pin where the center of rotation was within the boat he relocated the center of rotation to a point just below the hull and moved his centerboard on a semi-circle slot. This enabled the board to have a somewhat lower profile in the hull, though it's aspect ratio in use necessarily increased as consequence (not necessarily a bad thing). I have not read anything more from him since so I cannot say how his own efforts worked out for him in the long run.

Light outriggers (you're not going into heavy seas in a Wyoming anyway) amounting to no more than 10% displacement or so (i.e. as with a stabilized monohull rather than a trimaran) could be dismounted for transport or docking or if encountering an upset mob of purists .

Has anyone tried skin-on-frame amas for such fare? As has been pointed out: the design is already sorted out and so if you want to experiment best not to have to commit yourself in terms of overall appearance or additional investment. With small SoF amas and a suitable support structure you could play around with how much buoyancy they gave, their shape -- different iterations would not be expensive in time or materials to make -- and possibly even how they are positioned relative to the hull; and, if in the end you decided you didn't like them it wouldn't be a big deal to remove them and hide/remove their former mounting gear.

 

What is this perceived need for stabilization?

 

Comfortable stability for sharpies with floating amas

Thanks Rurudyne for your positive input. As I am not a Bolger purist, I don't care about others aesthetic feelings. General public don't find Bolger design as fashionable. I find beauty in Bolger design for its' design concept. Maximize space, efficiency and function at minimal cost to environment and pocket. The OP wants Wyoming for calmer waters but my needs are 85% offshore. The thread discussion should be performance oriented in technical terms. OP wanted to see if Wyoming can be fitted with amas like trimaran for improving stability to cruise with his wife. For that matter, let's say objective is to improve stability of small miniature destroyer hull form (long, rounded, rectangular hull) with amas. Far as aesthetics go, I prefer stylized work boat (lobster boat, tugboat, NPW salmon fishing boat), early 20th century and ultra modern looks.

PAR and others on stability, the stability ASM (OP) mentioned here is NOT a hull stability whether it will sink or not. The stability ASM wants to satisfy is stability his wife feels comfortable at. And, I am also seeking the same comfortable stability. The minimal stabilization I need to attract family/friends for long camping like cruise on water is a catamaran without snap roll motions. So I am looking for a catamaran design that will meet all my requirements but mono hulls have certain values such as carrying capacity and lower deck height (more comfort at sea). The trimarans are even less carrying capacity than the catamaran and much more work to build. And the most current design trimarans have constant rolls since they are designed to submerge one ama at a time.



The stabilizing sail and rocker plates are valued by some boaties but not by typical landlubbers. Latest gyro stabilizer are getting much better but it takes too much space in a narrow 35'-50' boat.

https://www.youtube.com/watch?v=JQO2a52Qd6M

The thin floating amas with retractability seems to be workable solutioin and I would like to discuss whether it is so. The amas should be low buoyancy and not a light-weight, they should work together to reduce amas vertical travel speed at slowest rate. Low buoyancy will cause slow submersion and weight of opposing ama should resist quick lift above water surface. Well that is my theory, but I would appreciate any input from experienced experts whether low buoyancy amas will stabilize smaller boat rolls and pitches with out any severe consquences.

 

Par,

Can't speak for ASM or Noah, naturally, but since my own desires are for something a trifle on the tall side for its beam in the way of a modest sidewheel houseboat, I've been interested in a variation of the stabilized monohull concept for a while now ("variation" in that the LBR is just a smidgeon under 5:1 in the largest version I could possibly expect to be able to build, so not really slender).

I'd actually contemplated skin on frame for my initial amas, if I ever get to build, for precisely the reason given: the possibility of experimenting without a lot of added cost.

 

Noah, while I'm not sure where I read it, I have read that insofar as it is prudent to do so it can be wise to keep the weight down far from the centerline. It was claimed that weight out wide, or extreme front/back, has a tendency to make motions worse rather than better.

As I understand the stabilized monohull concept, the relatively low displacement of the amas means that they may not respond as rapidly to rolling as the large amas of a trimaran will, giving them a longer roll period that is more monohull-like: you don't need them to be heavy to dampen rolling. As for their placement, I've seen statements that they should be submerged like normal hulls to just kissing the water. Someone like a NA could help us there ... though there may be no truly "right" answer I suppose.

There is a paper I came across a while back that addresses resistance reduction for these — full title being "Numerical and Experimental Study of Wave Forms for Trimaran Hull Forms", http://www.hiper08.unina.it/cd hiper 08/HTML/Papers/11- Maynard_PRASANTA.pdf — that may be of help. Another that I've got is "Design and Hydrodynamic Performance of Trimaran Displacement Ships", http://discovery.ucl.ac.uk/1349379/1/342546.pdf .



PS: I was trying to be funny with those earlier fan or purist comments. I hope that came across.

 

There is a third paper that I just noticed I had on my iPad called "Roll Stabilization with Short Wings": a somewhat inadequate title because what it's really about is two rows of staggered "short wings" in place of the normal bilge keel. I also just noticed why I'd eventually forgot about it: that the conclusion section says it is very effective in the 15-25 kt range which is higher than my desired range of speeds; also seems like they say it is slightly less effective than a regular bilge keel when at rest. That and it is definitely someone's still active patent (though I suppose the worst they can do if you ask them nicely is to say no).

Still: http://onlinelibrary.wiley.com/stor...F0F52FB77613A3.f02t03?v=1&t=hvsjg0u2&c470cf20

 

Amas stabilized narrow hull motorsailer

Rurudyne, I think we are on same wavelength now. When I said 'not lightweight' it doesn't mean heavy. I agree that all weight should be near COG (and balanced longtudinally) so any motion doesn't accumulate into harmonic motion or accelerate roll/pitch motions. My amas (floats) would be low buoyancy and enough weight possibly from longer akas (cross bar), not from heavier amas.

Now, can this sharpie hull with stabilizing amas have a dory hull to improve LBR (~8:1) when lightly displaced and have still be seaworthy at maximum displacement (~5:1)? This still will have most of sharpie benefits as motorsailer too.
The amas should be deep V bottomed hull to minimize slapping and easier roll motion. The top of the amas may be v shaped or semi-circle. My amas hull design would have been made with same material as main hull. Light yet strong floats with maybe built in ballast.

What would be the merits of SOF amas? What is the shape of SOF amas? SOF kayak as amas may have some desirability for me, but the flat hull bottom and uneven underwater SOF hull shape will induce too much drag IMO. Although SOF framing design can be such that drag can be minimized.

 

As I've said: the merit is in the area of cost, though I suppose construction time too, if one were to experiment with different amas particulars for a given main hull. Thus a few different shapes, lengths, fine placement fore/aft, or degrees of immersion, can be tinkered with but at less expense or time involved than if all were properly framed and glassed only to be used until those trials were over. Then the final ama, one backed with some confidence that it "may be Scottish", to adopt a Mike Meyersism, to be used could be made conventionally.

I see no compelling reason why a skin of frame boat has to be kayak-like with a flat bottom, it is just a different way to cover a frame or parts of a frame (if a design had features, like a step, that couldn't be fabric covered those bits could be done in wood). I wouldn't be above using it unconventionally either, say for a fender/house for my paddlewheel(s), in order to save weight where it'll do me nothing but harm if I built heavier.

Now about your dory hull, I see your point, given how some of these, like the Grand Banks type, pick up beam as they are loaded. It's a neat idea that let's the boat be driven very easily when lightly loaded. Essentially your's would be a design intended to loaded down even if that's not the case. Since your hull isn't super duper narrow the only concern I have (I may be wrong) lay with the wing structure because the more you press down on those amas the more you're laying into those wings too. If, as you say, you're wanting to spend much of your time where it gets rough easier these are the parts that I would want to be most concerned about and this is the part that will probably be best served by a professional's efforts.

 

Dory Sharpie hull with Light Flexible Amas

This was referenced to my liking of SOF kayak as the floats and it such case 'my' SOF kayak floats will be draggy. Sorry it wasn't very clear in my previous posting. As mentioned above, light SOF amas has a merit during development and for an application different than mine.

You got that correct. When loaded for a daytrip or an weekend trip, the dory main hull will be light and narrow (8:1) and for a multi week trip, the hull will be at maximum displacement with provisions (5:1). I am hoping for a semi-planing speed if there is a need, hence I am keeping somewhat of a flat sharpie hull bottom.
As for your concern about the stress on the akas (wing) and burying of amas should be minimal. Since this boat is trailerable, the akas are folding type. There is some ability to adjust angle of akas. Also, the akas should be long and should have flexible properties to accomodate various water level or to handle waves and not roll the main hull when one ama is buoyed. Unlike rigid fixed wing like akas of modern trimaran, I am leaning toward flexible shock dampening type of Polynesian Proa akas that has enough stiffness to support some passenger weight and toys occasionally.