What to do that Amas (Outriggers) aren't "dead space" for a Tri ?

[Skip JayR]

Within my own search for a Trimaran, by sure it will be a "used one" many different questions running through my head... Since couple of weeks I have one as following in mind:

What to do that Amas (Outriggers) aren't "dead space" for a Tri ?

I recommend for better understanding that I search for a Trimaran where living + working (mostly brainwork on computers) is possible. The racing performance is not of highest priority but giving me the chance to come from A to B (>20 knots on the log)... more important on board of a Trimaran to get the maximum out of space in the centre hull. (Rec.: I wont start here some discusssions about the alternative of a roomy cruising catamaran which I know by sailing and living on them.)

... as we see Amas are just "dead zone", nothing else than floaters with the function of "righting moment" (and eventually "wave piercing") being connected by cross beams (akas) with the main hull.

I have seen amas on 30-40 Footers with no single space in side.... even no single hutch window. Just a screwd plate as "inspection hole", e.g. for the rudder pole.

... simply glas fibre epoxy, carbon or marine plywood wrapping "space of air" for uplifting moment.... eventually with some trimming units, e.g. uplifting foils.

What to do with kind of bigger cruising trimaran, one gets the chance to buy ???

Taking the saw, open the ama for creating some extra storage room with installing 1, 2 or 3 hatch windows ?? (In the picture its a Farrier F-82 in Turkey)

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If possible... what kind of storage ?? - Packing each two of 4 heavy weighted gel batteries into the port and starbord ama to get more space in the centre hull ? Or just keeping it light weighted for storage of little things like fenders and sheets in it ? - Or just glue some solar panels on it ?

Or creating something more valuable space, e.g. integrating a berth (as known from Wharram Catamarans) or a toilet ?

No joke... the toilet is seen on the starbord ama of Trimaran Tritium ... see vid starting at 02:49...
https://www.youtube.com/watch?v=9-0iZpVv8R8


Feel free to share how you expanded your amas into some valuable extra space... without damaging the sailing abilities and substance of the boat.

 

[Gary Baigent]

Unless you have a narrow overall beam, very, very high buoyancy floats (like the 1950s early '60s slow and heavy cruising trimaran designs), then filling floats with accommodation or equipment of later trimaran designs is totally unsafe (for leeward float) - but water ballast in the windward float can be very useful, if beams are designed to carry the heavier weight and loads; however it would be suicidal to carry water ballast (or heavy gear) in the leeward float - unless that is your purpose, capsizing over it I mean.
So the "dead zone" to leeward as you call it, although empty and appears wasted, has a fairly essential purpose, like retaining power, stability and buoyancy so that you're not shaking hands with Mr. Death.
Alternatively you can reduce the dead zone floats to small flotation but carry foils to compensate the low stability.
Maybe, if you are concerned with wasted space, that is the answer for you.

 

[Skip JayR]

So the "dead zone" to leeward...

I am aware about the risks... and I know from the ORMA 60 they used Water ballast tanks. 6 water ballast hull sections in each 57 foot ama. The Virbac-Paprec MOD70 had a 350 liter water ballast tank in the transom in the interests of keeping the bows out. Okeys... 60 and 70 footer are a different league... and for racing. But still nothing against the Open 60 Vendee Globe round-the-world vessels, designed for variable displacement. E.g. Xena built in Australia had a standard displacement of 68 tons including 3 tons of variable water ballast. . Another story...

Let's go back to the F40 and start with a scenario to get a more clear picture: E.g. Lets assume, we'd need a big Battery bank (not a small one) to run all the elctronic devices on board (for working).

Instead packing these batteries in the centre hull, then probably only two can be stored (the heavy weighted gel batteries of 45 kg each).... with the reconfiguration in each outrigger are deposited 3 or 4 leight weighted batteries. I suppose they wont have a heavily bouncing effect as the batteries can be positioned neutral for the longitudinal trim 2 (+) against 2 (-).

There exist light weighted batteries of 25 kg each in the market. So in total each side, port and starboard ama max. 75-100 kgs... plus some cables. Converter will be kept centralized in the mainhull. Related to the total displacement a difference of maybe 60-110 kgs. The equivalent of one crew member, roughly.

Regularly a floater has the volume of 1.8-2 x of the complete displacement. As Trimarans are leight weighted, I'd calculate for the cruising version of a 40 footer max. 4-4.5 tons in total (as given by the designer); one float has something between 7.2 - 9 tons volume.

So packing on each side 75-100 kgs is roughly 1% and equally to having extra 2 people on board (inclusive luggage), e.g. a 4 headed crew. If the Trimaran is sailed short handed, max 2 persons, the "overweight" by the two battery banks might be compensated, isnt ?

I am not a naval engineer or designer... just try to figure out some possibilities maybe sounds nonsense ???

 

[cavalier mk2]

These questions are going to give Gary the horrors, he takes minimal to a smaller dimension. I think it unfortunate that tris have just become associated with speed because the configuration is well suited for cruising too.

I'll repeat my cruising world post that amas are best suited for bulky light items if storage is used. Weight must be kept out of the ends to preserve diagonal stability. Boat payload is not increased but carrying weight in the amas changes the roll moment of inertia slowing the boat's motion. This can be good or bad depending on sea state and boat type. Things stowed in amas should be things that can be easily moved in my opinion. Fresh water that can be transfered would work, batteries would best be centralized imho.

I barnstorm a relic but it is excellent for our purpose of fast wilderness cruising and exploration. We need to haul things like canoes and mountain bikes and are willing to trade a few knots for the internal volume, payload and deck space to pull it off. And we can do it with more than 2 people. I think you need to rethink your design purpose. A formula 40 is a beautiful fast racer or dayboat but isn't well suited to living aboard. For a suggestion find something to simulate the space and headroom you are contemplating and practice moving around in it, cooking etc....then have your friends over.

Space can still be fast if it isn't filled up and is a true luxury. A cruiser/racer design would be more versatile and dryer than a overloaded racer. Back when they were campaigning Newick's 40' Ocean Surfer it was nicknamed Ocean Suffer for the firehose treatment. In cold wet climes being dry counts for a lot. Try listing out your requirements then look for designs that fit.

 

[Rurudyne]

Speaking as one who actually likes those old slower cruising designs (if I won the lottery that I never buy ticks for that 104' Horstman design would make for a nice extended-family cruiser): I don't know if this will be of any use but I read somewhere that as a matter of comfort it's generally a good idea to keep weight away from the extremes in any boat, either fore/aft or side-to-side. This is because weight farther to the extremes tends to increase the motions of the boat.

Trimarans tend to be comfortable because, while their motions may be quick, they are not large. Also, accommodations tend to be lower down near the waterline which helps the range of motions remain small. This is why some credit tris as being more comfortable than similar cats who have their weight concentrated farther out and may also have higher accommodations if using the bridge deck.

When a cruising trimaran has heavy accommodations in the amas the accommodations are still low near the waterline so even if the up-down is larger and still quick there's not a lot of rolling in with that — same as with a cruising catamaran. The difference is that the cruising trimaran has less of its displacement farther out so even if, as on some designs, there are accommodations higher up there, weight and displacement are more centrally supported than with a cruising cat. I have absolutely no idea how important that really is for any given design, just that it could matter.

 

[cavalier mk2]

Weight spread evenly out into both amas actually does slow the roll. The analogy I use is its like a longer or heavier tight rope walking pole. This can easily be tested on any tri by moving crew out to the sides evenly.

 

[Rurudyne]

Weight spread evenly out into both amas actually does slow the roll. The analogy I use is its like a longer or heavier tight rope walking pole. This can easily be tested on any tri by moving crew out to the sides evenly.

Increased amplitude is what I thought I was getting at. Sorry if I wasn't clear enough (I usually blame the writer, especially if me, for any lack of clarity ... it's why my personal motto as a writer is: "The last edit you do is one edit too few.").

 

[cavalier mk2]

There is a big difference between pitch and roll on a tri as weight is moved to the extremes. The ama length and sail pressure provide much more damping for roll than the fine hull ends do for pitch.

Just adding weight into the windward ama makes sense from the sail power perspective. Moving the fresh water supply eliminates the parasite weight of pumping in seawater. These things only make sense on long tacks though. For cruising you are better off carrying your light bulky things like fenders, garbage and recycling in the amas that use up that cabin space luxury . For cruising these things should be carried evenly in case of getting caught aback etc... And there shouldn't be enough weight out there to make a difference.

The big cruising tris are really like 3 hull cats compared to modern square tris. When the cabins cover the amas they are still kept light, used as hallways for wing bunks and a place for another head.

 

[Doug Lord]

60' Serena

Jay, a friend of mine designed and built this tri in California in the 60's and early 70's and sailed(most of the way) from there to Titusville ,Florida. Meticulous workmanship. I like the twin outside cockpits and inside pilothouse.
The amas had full headroom.
click on picture for larger view:

 

[Skip JayR]

The solution on board of a Dragonfly 35

I'll repeat my cruising world post that amas are best suited for bulky light items if storage is used.

yep... thats why I started spinning around... after I have seen, that it is realized on a Dragonfly 35 Tri. As the Danish constructors build sportive Tris I suppose they know what they are doing. Cant be wrong...

Just did some screenshots from the promo video...

Here the video you can see the astern hatch opened from 01:49 min.
https://www.youtube.com/watch?v=oh4q2bt61EY


Such paddling kayaks can have a weight between 65-85 pounds roughly. This would be the equivalent for round about two leight-weighted A123 Military Batteries (round about 20 kg each) for long term use.

The Dragonfly 35 has another hutch window on deckside of the amas... so some more storage there...

Just by feeling I'd like to have on a 35-40 foot Trimaran extra storage weight of 150-200 kilogrammes, each side port + starbord. - It can be compensated by a higher mast, bigger main sail for righting moment, e.g. a 40 Foot Trimaran has a 60 Foot Mast... and some uplifting foils in the amas plus more stiffy construction materials to connect the cross beams safely, e.g. using foam-kevlar-epoxy.

Would be interesting to make some detailled cost calculations. Having 300-400 kg more transportation volume in the amas makes sense for long distance cruising Trimarans, isnt ? I'd like to get free 300-400 kgs more volume in the main hull using for other equipment.

With wave piercing bows the negatiely bumping effect of heavier weight shouldnt be too extreme. I will ask some multihull naval architects I know to get a more clear picture about such items...

 

[Rurudyne]

Jay, a friend of mine designed and built this tri in California in the 60's and early 70's and sailed(most of the way) from there to Titusville ,Florida. Meticulous workmanship. I like the twin outside cockpits and inside pilothouse.
The amas had full headroom.
click on picture for larger view:

I've seen that boat before. Love the way they handled the transom.

 

[Skip JayR]

Bridge Deck Trimarans of the 60th/70ths...

Jay, a friend of mine designed and built this tri in California in the 60's and early 70's and sailed(most of the way)...

Yes typically design of that time. Similarly with the Pivers. Real scaring fighting monsters...

I cant help me when seeing these "room miracles" the deck design remembers me a Russian war ship and the silent movie of 1925: "Броненосец Потёмкин/Bronenossez Potjomkin".

Trailer of this movie with English subtitles...
http://www.youtube.com/watch?v=tCZLlBGJq5s

(Rec.: if one want watch this movie, it is available in fully length on YT.)

The thematic of this movie is around the Russian battle ship Potemkin (original name: "Knjas Potjomkin Tawritscheski") built 1904/05.

I suppose for the first start (as my first Trimaran boat) I will take something sportive.... and maybe in some years expand into something "bigger with more space".

Some Pivers now 50 years old are still floating and cheaply for sales...

Impressive underwater ship of the central hull such a 40 Foot Piver Victress

I suppose such a boat would let me feel too old.

 

[Skip JayR]

more loads in the amas + water ballast trimming (windward)

Moving the fresh water supply eliminates the parasite weight of pumping in seawater. These things only make sense on long tacks though.

hm... yet I have not thought about that idea... naturally I know about water ballast, but in my brain its mainly linked with "racing boats" (and monohulls). But I like it... smart.

Actually I have a 40 footer I am negotiationg to buy. This week I had a good talk with the designer. (Guys, dont ask me after the name of the boat or the designer. You will undertsand that I keep it silently for now.)

The boat has a water tank capacity of 500 litres... which is huge for a racing-cruising Trimaran of 40 Foot length. It is already planned a water maker for this boat to be independent from water delivery services which can become very costly and time intensive in some places on this planet. So not urgently it is needed to have the 500 litre tank steadily filled.

Total weight of the boat - as planned by the designer should be 3.6 tons... actually built at round about 4 tons (by some decisions made from the owners + warft builders).

Putting the batteries into the amas, each 3-4 leight weighted ones 75-100 kilogrammes and then balancing it newly with a fresh water ballast system windward 200 litres might be an interesting option. Cool... I will think about.

An electric pump needs round about 2 minutes for a 600 litre tank... as Van Gorkom Yacht design realized it. Quickly done in the time dimensions of long distance sailing and well preplanned manoevers (without any regatta hectic).

.

Not too complicated...

Just reading about.... "Why a Water Ballast System is Worth Thinking About"

Does anybody know a sportive Cruising Trimaran where such a "trimming unit" with fresh water was installed ?

 

[cavalier mk2]

Another battery storage option to bring it inboard would be a external main hull fairing or something within the aka fairing near the root.

 

[Skip JayR]

Another battery storage option to bring it inboard would be a external main hull fairing...

Cavalier, the boat shall not become ugly .

It same should fit my esthetical taste, too.... beside covering the functionally needs. If not, I could find a way to install on deck the new TESLA POWERWALL (a fully battery backup system for electrification of a house) and the problem is solved..

So no change of the optical look as it is now. Only some very view changes I would allow, e.g. wave piercing bows... as done with the Triamran Pipeline3 (a Kurt Hughes design)...