Power Trimarans?

Richard...

Why do you do this; Throw-out broad statements of fact and then later get incensed to the point of tossing insults when someone suggests that you define the issues more distinctly?

Crag merely suggested that from his experience, you had missed the mark with your post. You come back with the "you should keep your mouth shut when you don't know what you're talking about!" routine.

Disagreements are fine as long as you keep them civil. This comment you posted should not be a part of your expressed lexicon if you want to remain well-regarded. It sounds very much like a bully who wishes to shout-down the opposition.

 

"So could a 40 foot power boat with a 7 foot beam be built in such a way as to be stable at sea? I'm not sure if that hull form (with a sharp, plumb bow) would even qualify as something you could use as the center of a tri as it might be too beamy?"

WE are still looking to build a similar boat 39ft LOA 7.6 BOA with an Atkin Box keel and reverse deadrise.Shippable in a container and easily trailerable.

One huge advantage is the boat would be beachable , or can run aground with no damage. We like it for the ability to stand in a shipping container and the claimed efficiency at SL below3.

18K would be a fine cruise speed , and with a simple interior should go in under the EU 8,800 lb weight .

With much help from Rick W we believe great COASTAL CRUISING COULD BE DONE , yet the boat would be safe to make an offshore passage.

There are threads BOX BOAT , and others that discuss this perhaps modest (Below SL3) speed efficient concept.

WE hope for 5nm/gal at cruise, with Ivecio mechanical injection 6 cyl diesel

FF

 

5 nm/gal at 18 knots would be quite an impressive achievement in a four-tonne boat, Fred. The concept certainly sounds like it's worth exploring.

As to CatBuilder's requirements. Given the European canal-cruising use profile, long and slim would seem to be the order of the day. (I should note that in the Canadian canal systems I cruise, lockage is charged by length, but beam is not penalized so long as you can fit through the gates. Thus, a beamy multi has an advantage here that it does not have in many European systems.)

But then there's the issue of ocean crossing. A 40' x 7-8' power cruiser is not a large or heavy boat. Ocean crossing under power requires substantial fuel reserves; if a large portion of your displacement is gas tanks, it may be hard to fit enough room to live comfortably while underway.

A kite sail rig applies fairly simple (although often rather large) forces to the hull, at an attachment point much closer to the waterline than any masted rig. As a result, the heeling moments would likely be much lower than for a conventional rig. I think it should be feasible to design a powerboat that could have a kite rig added at a later date, without compromising any of its powerboat characteristics.

If you look at most of the big ocean-going power tris (Earthrace, any of the big Nigel Irens record-hunters), it becomes evident that most of them are really just skinny monohulls with little "training wheels" as outriggers to keep them upright. They end up being extremely long for their weight and usable volume. In smaller sizes, I think there's something to be said for proportionally larger outriggers, especially when you're trying to get a lot of usable deck space in a given length. But if container shipping and really narrow canals are in the picture, sticking with just a single self-righting hull might make more sense. It sounds like a 40', 5 tonne version of the 83', 40 tonne Dashew FPB is an appealing concept?

 

Look at posts #2 #3 Matt, he is exactly at that point.


Here is another interesting concept of a power tri

http://www.trybrid.org/trimaran/about/the-long-thin-hull/

 

You guys are great at keeping a man thinking!

I have been reading this forum like I have a wire going straight in to my brain. I have learned so much in only a week or so here. Thank you for all the insight.

I think I am after a Dashew style boat, but was thinking trimaran (or maybe some flopper stoppers) more for anchoring comfort than anything else.

There are a lot of outside (not boat related) factors here I am trying to consider as well:

*Low build cost
*Longevity (lasting many years both in terms of hull and machinery)
*Canals
*Portability
*Comfort

 

Just some thoughts.
You have to give up the idea of a too narrow hull and a too lightweight vessel, IMHO. 40´by 7´something is just not sensible, where would you live in? A deckhouse will be impossible and the hull will be so narrow, thats close to living in a telefon box (European style). The windhorse concept cannot be scaled down to a 40ft boat I think.
But the designs I already pointed to, are very, very economical vessels and able to fit your needs in my opinion. Though much heavier than the original idea you had.
Give this a look too:
http://www.kastenmarine.com/greatheart36.htm

No, I do´nt get a commission. They are just nice and well designed.

And maybe I have missed that, but, why portable?

Regards
Richard

 

Richard, a very similar boat (although it is a sailboat) is this one:

https://www.yachtworld.com/core/lis...rrency=USD&access=Public&listing_id=1852&url=

She shares the same features and dimensions, with the exception of needing a heavy power plant. The interior is liveable enough if it allows me to come back to see the world on a budget. I already live aboard a 34' boat right now, yet she's a catamaran, so it's plenty of room.

I think you're right at 40' x 7', we are no longer talking about a Windhorse because the L/B ratio is growing much fatter.

I am looking to portability (shipping containers) to help facilitate an economic way to travel the world. Crossing an ocean on your own bottom is prohibitively expensive unless you build a Wharram style catamaran with all the low tech gear you can find. Container was to help offset costs.

 

>>>She shares the same features and dimensions, with the exception of needing a heavy power plant.<<<

and not to forget she has a heavy keel to keep her upright! A powerboat of that size would better not need that!?

 

Of course. I didn't say that because I figured it was obvious.

 

What about this?
http://www.multihulldesigns.com/designs_stock/38tri.html

 

"But then there's the issue of ocean crossing. A 40' x 7-8' power cruiser is not a large or heavy boat. Ocean crossing under power requires substantial fuel reserves;"


Ocean CRUISING would be fine for a boat of these dimensions,
a CROSSING would be done snug as a bug inside a 40ft steel container.

I would only hope the vessel she is being transported on has enough fuel.

Once a more modest coastal range is accepted 500mi? 750 mi? 1000,mi?

The weight and volume of the fuel are mostly a concern if the fuel is used as ballast , and the boat more dangerous in Light Ship condition .

Although these days with no discharge rules , a dual bladder tank might compensate .

Fuel out , waste water in.



FF

 

Exactly!

That's the type of boat I was picturing and I recently did take a look at Kurt's site. Looks like this has (mostly) been designed already.

 

I'm just receive the study plans for the tri trawler last week,I just love the comcept of this boat, like the idea of "trailerable"(a folding system would be perfect) but I dont kow if is good for an ocacional tripp to the Bahamas,I'm in florida.

 

It just has one serious disadvantage! (if not more) It will not fit in a 40´container! And just one centimeter too large for a standard container and you add a zero to your freight rate! Thats not much but we live in a metric world you know?