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Old 28-12-2007, 14:04   #1
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tuning tips for multihulls

from the vast wealth of knowledge on this site , what about a boat tuning thread ? there must be so many ideas on getting the most from our multihulls, we all decided to buy a faster breed of yacht - so what have we all learned ? put those tweaks into print , lets hear them - i will start the ball rolling . this year i moved my anchors and chain from the bow lockers to the mast foot lockers along with the windlass - result ? less pitching and weight centred to level hulls out . it also meant a shorter run for the power cables which means less power loss . the forward lockers are now dedicated to the fenders which have been cleverly filled with--air ! lets see your best tips ...
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Old 28-12-2007, 15:23   #2
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Getting weight in the center is always good. I moved my Spectra watermaker which the PO had mounted in the stern compartment to the center bilge next to the centerboard.

As the boat's water tank is in the bow(!) we only carry a small amount of water and make it as we go. Our sailing these days no longer consists of offshore passages, so we're never in any danger of running out.

On the future list (pending practicality) is moving the anchor chain and rode to a compartment which is currently a hanging locker which we don't really need Inside the boat it would be totally waterproof and have an overboard drain above the waterline.
I'll make a hawsepipe opening on the starboard deck for it nearly even with the mast.
(The anchor is already carried and deployed from the inner end of the starboard forward ama.)


Steve B.
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Old 29-12-2007, 06:06   #3
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This is a good thread, photos would be nice along the way.
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Old 29-12-2007, 08:47   #4
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In the decrease weight department, I am planning to modify my fuel delivery lines to enable either engine to draw/return fuel from/to either diesel tank. (Currently, only the port tank can supply the port engine and vice versa. I can't believe Catana didn't build in the flexibility to use only one tank from the beginning.) This will allow filling only one tank for those times when a long passage isn't in the near future and emptying the other for cleaning, etc. This will also permit filling the tanks from different sources and thus having some insurance over getting a bad batch of fuel.

Yes, running one tank full will offset the weight to one side or the other a bit, but, oh well.

Also in the decrease weight department, I think emptying beer bottles is a huge tuning benefit. Not only does it decrease weight, the more bottles I empty, the better tuned my sails look.

Dave
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Old 29-12-2007, 09:20   #5
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I agree about having flexibility with your fuel tanks, including a transfer pump between the two tanks, however, a couple things to consider are (and probably the reason manufacturers do it that way):
If you leave the valves in the wrong position you can pump all the return fuel into one tank, filling it up then start dumping fuel overboard through the tank vent.
By having separate isolated systems you prevent cross-contamination if one of your tanks gets the bugs.

I also like your idea of filling different tanks at different locations, that’s good thinking.

Now my question, I have been on a cat with twin dagger-boards, is it much different in handling then a single, center dagger-board?
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Old 29-12-2007, 10:19   #6
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We at African Cats build in 4 separate tanks all positioned on either side of the mast.
For shorter cruises the 2 inner tanks are filled and optionally we can open valves to increase tankage to 180 US gallons.
the left or right tank can be used and the back flow of diesel is also directed to the tank where the flow is set from.
In the save weight department we have made drastical effort to get the weight down from the original 9000 kilo,s or 20.000 lbs to the 5000 kilo (11000 LBS )that the last boat came out at.
Some of the weight saving where simple , taking the 50 meters of 10 mm galvanized
and change it for 25 meters of Duplex 8 mm chain and 25 meters of weighted line.
Just this change saved over 100 kilo or 220 LBS. chaging from glass windows to Lexan marguard saved another 115 kilo or 255 Lbs
The biggest single weight saver was taking the lead acid batteries out and putting in Lithium Ion Phosphate. this saved over 200 kilo,s or 440 LBS
All cabinets and locker spaces are build within 10 ft or 3 meters of the centre of gravity. the anchor chain locker is under the mast step together with the winch.
The generator and the batteries are mounted under the nav station and seatin area right on the centre of gravity.
We changed from Lewmar winches to Harken and Meissner winches and this was also a good one , 40 kilo,s ( 88 LBS ) less on the scale .
Are cats are build on 4 load cells so during the building time we can measure all weights coming on board and we can keep the weights at the right locations .
Another weight saver is chaging the porcelin Toilets most of you use to the RM 69 Plastic toilet, a weight saver of 25 k. or 55 LBS per toilet.
Changing from a normal powr distribution system to a Buss system saved 128 kilo,s or 280 LBS.
For the Rigid inflatable we changed from a 85 kilo Caribe to a self build carbon fiber and Hypalon Rigid inflatable in the same size but a weight of only 28 kilo.
Because of this change we could reduce the size and strenght of the davits for a weight saving of 85 kilo.The ouitboard became smaller in the process, before it was a 10 HP Suzuki 4 cycle long leg with a weight of 39 kilo,s excluding the tank and now we use a 6 HP Tohatsu 4 Cycle with a weight of 19,6 kilo with a build in tank.
All control lines where changed from normal polyester to Dyneema 36 kilo.
The side stays where changed from 12 mm Dyform to Dyneema side stays . 66 Kilo,s
The roof originally constructed with glass and foam is now constructed with Carbon Fiber 110 kilo.We left out the Gell and flow Coat and now use Spray paint the boat with Awl Grip.This saved 850 Kilo,s. Optionally we install a carbon fiber mast and Boom for 185 kilos of weight saved.
We left out all inner linings originally made in Fiberglass/Epoxy 225 Kilos
etc.etc.

Greetings
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Old 29-12-2007, 10:32   #7
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Originally Posted by mdfixitman View Post
If you leave the valves in the wrong position you can pump all the return fuel into one tank, filling it up then start dumping fuel overboard through the tank vent.
Yep, gotta not be stupid! But once I get the mod in, this is the way I was going to start transferring the contents from one tank to the other, considering I do not plan to install a transfer pump - I'll just use the one on the engines.

I have not sailed a single, center board cat since the early Stilettos. I don't expect there'd be much difference in handling, assuming the single board was big enough to do the job.

Dave
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Old 29-12-2007, 10:38   #8
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Of course a good way to loose about 6,000 lbs is to loose one of the engines, like the new Lagoon 420 Hybrid Diesel Electric. Interesting idea.

http://www.cruisingworld.com/boats-and-gear/boat-reviews-and-previews/lagoon-420-hybrid-mini-review-49367.html
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Old 29-12-2007, 10:45   #9
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Yes you are right they have lost one engine but How come the 420 weights well over 13.000 kilo,s and even misses one engine ?
They have gone wrong somewhere Just do not know where.
It is by far the heaviest 42 footer around !!!
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Old 29-12-2007, 10:51   #10
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fastcat , how do you keep your boats in the water! , fascinating to hear of all your weight reduction techniques , very inspiring . how can a mere mortal get the dyneema shrouds ? i am thinking of replacing mine before an atlantic trip next autumn , as its now 8 years old / dyneema , what can i use for end terminals , bottle screws etc.?
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Old 29-12-2007, 10:58   #11
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This is a good thread, photos would be nice along the way.
Here you go.

Steve B.
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Old 29-12-2007, 11:12   #12
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Fastcat,

I'd appreciate a link for the RM69 plastic toilet as my original (nylon?) head is showing its age.

I'd also appreciate a link for the Lithium batteries.

Thanks in advance,

Steve B.
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Old 29-12-2007, 11:33   #13
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FastCat - That is an impressive vessel! I will have to take a closer look.
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Old 29-12-2007, 12:05   #14
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For the RM toilets the link is Raske en Van Der Meyde, Marine Toilets
The Link for the Lithium Ion batteries is Valence Technology | Products | Epoch Power Systems | Overview
for the Dyneema rigging http://www.gottifredimaffioli.com/en/news/news6.php
Hallo Gramos we use a Rocna 25 kilo anchor to keep the boats in the water.
A fantastic anchor down from a 40 Kilo Plow anchor used before.
Since our cat went on a weight watchers diet we have gained 30 % in speed are sailing closer to the wind than ever before and the most fantastic thing is the average speed gains with light winds are over 50 % and most of the times we have wind speeds of between 8 and 20 knots
10 knots of wind speed at 90 apparent gives us 9 knots of speed and I intend to improve on that to 10 knots of speed
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Old 29-12-2007, 12:30   #15
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Another weight saver is chaging the porcelin Toilets most of you use to the RM 69 Plastic toilet, a weight saver of 25 k. or 55 LBS per toilet.
Yikes! What toilet are you comparing to? My Jabsco/Par only weighs ~20lbs and it is porcelain.

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