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This was just dropped from AUD$450k to AUD$375k today. One for the lovers of traditional, but with modern materials.

https://www.boatsonline.com.au/boat...yle-timber-motor-sailer-brand-new-2022/286347

AND

https://www.boatsonline.com.au/boats-for-sale/used/power-boats/2022-timber-cruiser/279879

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Art said:
I would think it not to difficult to engineer some form of bow buoyancy design that would kinda split the difference between submarining and bouncing upward too feely into/onto waves.
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Wave piercing has several advantages.

Boat goes faster. Wave piercing is usually done with very fine entries. Boat doesn’t stall hitting a wave but rather pierces. There’s enough reserve buoyancy that she rises more slowly so pitches considerably less giving a much smoother ride. There’s sufficient reserve buoyancy that she rises to meet the next wave. For LOD there’s more LWL which also improves hull speed at displacement speeds.
Downsides are how to run ground gear so during deployment and retrieval neither chain nor anchor strikes the hull. Also as stated above more green water over the foredeck in sporty conditions. Both are solvable. For ground gear have snubbers off the bow and short sprits off the side so roller(s) are free of the hull or a longer sprit off the midline. For green water divert flow to sides in forward third of the boat.
Question is whether the modifications required for a reverse stem are worth it. Or is a very fine entry with extremely low prismatic coefficient sufficient. Think sometimes the reserve stem is done for a “sexy” look. But you never know without studying tank testing and computer modeling. The fine points are above my pay grade
 
Hippocampus said:
Wave piercing has several advantages.

Boat goes faster. Wave piercing is usually done with very fine entries. Boat doesn’t stall hitting a wave but rather pierces. There’s enough reserve buoyancy that she rises more slowly so pitches considerably less giving a much smoother ride. There’s sufficient reserve buoyancy that she rises to meet the next wave. For LOD there’s more LWL which also improves hull speed at displacement speeds.
Downsides are how to run ground gear so during deployment and retrieval neither chain nor anchor strikes the hull. Also as stated above more green water over the foredeck in sporty conditions. Both are solvable. For ground gear have snubbers off the bow and short sprits off the side so roller(s) are free of the hull or a longer sprit off the midline. For green water divert flow to sides in forward third of the boat.
Question is whether the modifications required for a reverse stem are worth it. Or is a very fine entry with extremely low prismatic coefficient sufficient. Think sometimes the reserve stem is done for a “sexy” look. But you never know without studying tank testing and computer modeling. The fine points are above my pay grade
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My engineer could figure that out [not that he/we have time nor desire to do so].

My company works in-depth with fluid dynamics regarding heated airflow buoyance, convection/turbulence [CFD]. Looking at the video of that boat's bow "wave piercing"... seems to me that computer programed, quick action manipulatable, streamline water-foils could be just above waterline. therein enabling the bow's entry profile to rapidly adjust to wave/speed conditions at hand. In essence... keep horizontal plane of the boat closer to a 90 degree angle with water plane. That would accomplish a better ride [reduced bucking] and less fuel burn, due to less friction area and fewer speed adjustments.

I see these foils as inflatable/flexible materials. Maybe 20' long above waterline on both sides. With air pumps [or knuckled internal "stretchers"] for their contours to be quickly adjustable by computer program that understands best shape needed at that time to not allow submarining while also not having the bow climb the wave.

Cost - $250K +/- But, heck what's a couple extra $100K when money's no object compared to comfort when you're aboard a multi million $$$$ boat in water conditions you should not be in the first place!!?? :dance: :thumb:

We also work a lot with materials... :D
 
long-cours.62 said:
Don't know if this one was already posted ?

https://www.yachtworld.fr/yacht/1993-malcolm-tennant-awesome-8609853/
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Nice boat

But one of the things I really miss about multihulls is the shallow draft.
CS hull shape takes that away.
And, makes a narrower hull internally.

But, if only aiming at speeds around 14knots as a max, the CS hull shape is not needed.
It can be argued, as most aluminium Ferries don't use it and travel at high speed, that it is not needed at all.

Personally, shallow draft and high internal space is what I would insist on.
 
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Simi 60 said:
It can be argued, as most aluminium Ferries don't use it and travel at high speed, that it is not needed at all.

Personally, shallow draft and high internal space is what I would insist on.
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I think there might be a difference in fuel economy though. Those fast aluminum ferries are hungry.

I'd like a 40' version of that boat.
 
DDW said:
I think there might be a difference in fuel economy though. Those fast aluminum ferries are hungry.

I'd like a 40' version of that boat.
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There is a 45 foot version of the Tennant powercat stranded out in Fiji or somewhere like that and it is a very good value. With bladders already on the boat you could get it to Australia I think. It looks to be quite well kept.

I think Multihull Solutions has the listing and have had it for a long time.

Scoop and score....
 
DDW said:
I think there might be a difference in fuel economy though. Those fast aluminum ferries are hungry.
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Well they do carry a hundred or more passengers, so plenty of weight and weight needs HP.

I think that has more effect on fuel economy than hull shape.
 
klee wyck said:
There is a 45 foot version of the Tennant powercat stranded out in Fiji or somewhere like that and it is a very good value. With bladders already on the boat you could get it to Australia I think. It looks to be quite well kept.

I think Multihull Solutions has the listing and have had it for a long time.

Scoop and score....
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Yeah, have seen that. If I was looking for a boat I might be looking that direction. I think the location has depressed the price considerably - though it would cost a bit to get to the NA West coast. Tennant did some 40 ish boats that were said to be trans oceanic capable, I don't think that particular example was set up that way, but would do what I want. Still like to stay <40 though.
 
There is a 45 foot version of the Tennant powercat stranded out in Fiji or somewhere like that
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I looked at the Multihull Solutions site; can someone link me to that cat, please; I could not find it there.
 
Mako said:
I like the island in the galley. Gotta figure out how to fit one in my next boat.
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An island doesn't necessarily need a ton of space to fit. My boat has a peninsula in the galley for extra counter space, an eating space, and to divide the galley from the salon. And we're only a 38 footer.

I don't have a great picture of it, but here's one from the salon looking into the galley while I was using the bar top as a desk one day. There's a counter with cabinets below it and the sink just beyond the bar top (not visible in the picture). Galley is open on the right side of the picture where the bar top ends across from the stove.
 

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BruceK said:
Fits the thread nicely:
1_4.jpg

https://www.boatsonline.com.au/boat...ered-and-in-excellent-order-throughout/125763
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Interesting pics. Some appear to much newer than others. Most of the outside pics don't show the stabilizer installation . . . wonder when they were added, and what the boat looks like NOW?

Otherwise, really nice, older electronics, but they can be upgraded. I really like the engine room, but am curious why the Gardner required rebuilding . . . .Maybe they purchased it used, and had it rebuilt prior to installing it in the boat?
 
slowgoesit said:
Interesting pics. Some appear to much newer than others. Most of the outside pics don't show the stabilizer installation . . . wonder when they were added, and what the boat looks like NOW?

Otherwise, really nice, older electronics, but they can be upgraded. I really like the engine room, but am curious why the Gardner required rebuilding . . . .Maybe they purchased it used, and had it rebuilt prior to installing it in the boat?
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The stabilizers look carefully tailored to the hull,suggesting thought went into them.
Could be wrong, but are there any new Gardners? Maybe the 'new" ones are all "old"ones rebuilt as they gradually wear out and get rebuilt.
< Had that axe for 30 years, 3 new handles, 2 new heads, a great axe>:)
 
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Mako said:
Yes an interesting vessel but I’m not so sure about those bat wings
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Pretty well known method of stabilization, just not as well known as fish and fins in the recreational world. In some parts of the world, bat wings or fish are the choices. Bat wings have a lot of advantages, but may not work quite as well as fish according to some research papers.
 
Batwing stabilisation is common in Australia, especially in Qld, and on commercial vessels. That powered installation looks excellent. I was looking at that vessel myself; it ticks a lot of boxes. @Mako: what don't you like about batwings?

If reducing roll is the goal, slight differences in efficiencies between the different solutions (hydraulic, paravane, batwing) IMHO are non-significant. For me, batwings offer decent stabilisation, and with the powered implementation on the boat we are talking about, much easier (and safer) to deploy than paravanes, I feel.
 
Kit_L said:
Batwing stabilisation is common in Australia, especially in Qld, and on commercial vessels. That powered installation looks excellent. I was looking at that vessel myself; it ticks a lot of boxes. @Mako: what don't you like about batwings?

If reducing roll is the goal, slight differences in efficiencies between the different solutions (hydraulic, paravane, batwing) IMHO are non-significant. For me, batwings offer decent stabilisation, and with the powered implementation on the boat we are talking about, much easier (and safer) to deploy than paravanes, I feel.
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Can't help but wonder what chance of bad effects to the hull in big seas if an in use Batwing stabilizer gets ripped off due to flotsam impact?
 
Art said:
Can't help but wonder what chance of bad effects to the hull in big seas if an in use Batwing stabilizer gets ripped off due to flotsam impact?
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I'd hope they're attached in a way that given a big enough impact, either the batwing itself breaks apart, or it breaks off the hull without tearing the hull apart. It's one of those structures you don't want to be super strong relative to the hull itself.
 
That is my understanding too, @rslifkin, that the inside of steel hulls are reinforced, and that the hinge mechanism is the sacrifice part (outside the hull), but I do not have personal knowledge of this aspect myself.

And the fishing boats that are the most common users of these devices are out in all weather, so can only assume that they work. I do know a yard that does these and if I get a chance to talk to a designer, I will report back.
 
Art said:
Can't help but wonder what chance of bad effects to the hull in big seas if an in use Batwing stabilizer gets ripped off due to flotsam impact?
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So I was asked what I didn't like about Batwings, and Art's comment above just about nails it. Have two of those giant appendages sticking out at the water-plane doesn't feel right. Catching lines to crab pots, fishing nets, logs, etc. Also, they are not active, just oversized rolling chocks. Unless they are hydrodynamical shaped for downforce, like paravanes. Anyway, those are just my thoughts, but if someone has owned some and can comment on what % roll reduction they estimate, it would be very helpful.
 
I'm not sure their detritus catching ability far exceeds fins or paravanes, and they can be retracted, fins can't.

Perhaps you haven't considered how they work: when rolling to starboard, the starboard wing sees a relative upflow of water and generates upward force, while the port wing sees a realtive downward flow and generates a downward force. You want a symmetric airfoil here because it helps going both ways, like fins. Parafoils can provide no upward force through the flexible line, only downward, and only one (the one trying to go up) is doing anything.

There is a research paper out of the University of Quebec comparing batwings and fish on sisterships. Sadly not in very challenging conditions, and they aren't really sisterships. The bottom line of that paper was they provided less roll control but still significant, and the local fishermen seem to prefer them due to safety and ease of deployment.

Sailors have known for centuries that a deep centerboard or daggerboard will reduce rolling, so not really a new concept.
 
You can find

Mako said:
So I was asked what I didn't like about Batwings, and Art's comment above just about nails it. Have two of those giant appendages sticking out at the water-plane doesn't feel right. Catching lines to crab pots, fishing nets, logs, etc. Also, they are not active, just oversized rolling chocks. Unless they are hydrodynamical shaped for downforce, like paravanes. Anyway, those are just my thoughts, but if someone has owned some and can comment on what % roll reduction they estimate, it would be very helpful.
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on Canadian website they made a report to compare this equipment to paravane (in term of drag, consumption, damping of roll etc )

But sorry I don't remember where :confused: normally I even load the PDf but :confused:
Alzheimer !?
 
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