Help me make a weight budget for a trimaran

[longjonsilver]

We are looking at buying a trimaran and are considering how big a sailboat we need/want. We see on many designers websites that both the dry and loaded weights are listed. As such one can figure out the payload. Right now we have a John Marples CC40 in our sights. Its payload is 2600 lbs. Target is cruising with a couple from New England to the West Indies and back for the winter. So we have the following listed on our spreadsheet:
Diesel 7.3 lbs/gallon
Water 8.3 lbs /gallon
Batteries 65 lbs each for golf cart batteries
Mantus 30 Kg anchor . 66 lbs
Fortress GX 37 18 lbs
Third anchor 35 lbs
Chain 5/16 150' .93 lbs/foot (3/8 1.41 lbs/ft)
People 2 @ 150 lbs each
Windsurfer 100 lbs each (estimate)
Dinghy 80 lbs

How much should we figure for food? Clothes? And all the other stuff i might have neglected to include?

thanks

jon

[longjonsilver]

Gemeinhardt flute and Yamaha guitar with gig bag 9 lbs
Icom IC-700 SSB radio telephone 18 lbs
Sextants 9 lbs
Binoculars 2 lbs
Full Propane Cylinder 37 lbs

[longjonsilver]

Fishing gear (so far) 18 lbs
2 full size bicycles with locks 44 lbs
12 volt Seafrost Refrigeration 105 lbs
8 life vests 7 lbs
Skin diving gear inc weight belt 10 lbs
Kitchen tools 46 lbs
2 harnesses 1 tether 4
Diesel Water Vapor Trap 1
Spinnaker and ATN Tacker 33
Bosuns Chair 4
Boat Hooks (2) 2
Spool 5/8 line 15
Spool 1/2 line and anchor hook 9
Sea Anchor and Flare kit 3
Wet skins (2) 2
Food at 5.5 lbs/person/day from DM Street from Gardner 20 days 2 people 220 lbs

i'm up to 2229 lbs with 5/16 chain and 2301 lbs with 3/8 chain

i have not included Jordan Series Drogue, Mast Ladder, Anchor rode, Flags, Radar reflector, Radar, Chart plotter, laptop, Solar panels, wind generator, BBQ and a bunch of other stuff that i will think of as time goes along.

[Boatguy30]

Some "basic gear" is include in the pre payload displacement numbers. So should need to count all anchors.

The windsurfers are something that is going to push you up there. But assuming the boat is built to spec and no heavy, 2600 of payload is plenty for a couple.

[Paul L]

Tools are heavy and required.
Dinghy outboard
Dive gear with wetsuits weighs more than you specd
Why no solar?
Engine fluids, oil, transmission, and filter spares
Epoxy and fiberglass for repairs
Dock lines and spare lines
Equipment manuals

[Anders]

We would not be able to go anywhere with only 2600 pounds payload. Just filling up the water and diesel tanks is close to half of that.
We have no bicycles, wind surfers or windgenerator and are rarely away from the shops for more than a few days.

[Cavalier MK2]

Couple quick notes. Only use a boat length of chain, make the rest rode.

Electrical is where you can save big in the battery dept. by streamlining your needs. Golf cart batteries?

The windsurfer weight seems high check the figures, they are also a bit impractical unless they can double as stand up paddle boards for exploring. I'd suggest a couple kayaks instead for weight and space savings as well as more practical exploration craft for the back waters. Add a sail to the dinghy for that and you'll still be ahead of 200 pounds.

[catsketcher]

The CC 40 is a dedicated cruising tri, you need to go and have a look at it.

We have a couple of sisterships of our cat. Most of them sit 50-70mm lower than ours. We have a simple fit out, they are luxurious. We can carry stuff to get our transom down, they start with their transoms in the water.

So check out the CC40 in real life. If its stern is high out of the water and it has a fair bit of gear on board then good, you can add lots more. If they have been silly and added a stained glass drinks cabinet, you can't take as much gear.

Probably the most useful thing to learn is the immersion rate. This tells you approximately how much weight will sink the boat a certain amount. The tri is 12m long on the waterline, about 1.6M (I am guessing here) wide on the waterline and has a prismatic co-efficient of 0.6 (ballpark figure). So area of waterplane is 12 x 1.6 x 0.6 = 11.52 metres squared.

Once you know the waterplane you can work out the immersion rate, which is the same as the volume depressed = Area x depth. So for 1cm the immersion rate = 11.52 x 0.01 = 0.115 m^3. The weight of 0.115 metres ^3 of water is 115kg (approx).

So if the boat is floating 8cm higher than designed waterline you can add 8x115 kg. If you can accept pushing her down another 4 cm you can add 4 x 115kg. All up total 1380kg.

But first you need to look at the boat. If she was built heavy then you have less payload to start with. Remember, you can't fudge this. A cruising boat with too little underwater volume is a bad way to start cruising.

Use the formula Lwl x waterline beam x 0.6 to quickly calculate the immersion rate of all the boats you look at. My wife and I lived on a tri that had a terribly low immersion rate - about 40kg/cm. (8.5 x 0.8 x 0.6) It was fun for a while but I would never recommend it.

About the windsurfers - I took mine a few cruises but ditched them afterwards. I was anchoring in nice calm bays out of the wind. I love taking kayaks though. Tris are great for taking kayaks and other light but large gear.

cheers

Phil

[catsketcher]

The CC40 was designed by a solid cruising guy so there should be heaps of payload - you just have to check that the builder and subsequent owners have not weighed her down over the years with heavy additions.

[longjonsilver]

Thanks everybody for your input. This really makes my decision easier!

Originally Posted by Boatguy30

Some "basic gear" is include in the pre payload displacement numbers. So should need to count all anchors.
But assuming the boat is built to spec and no heavy, 2600 of payload is plenty for a couple.

i have an email in to John Marples asking him what equipment is included in his "dry" weight.

Originally Posted by Paul L

Tools are heavy and required.
Dinghy outboard
Dive gear with wetsuits weighs more than you specd
Why no solar?
Engine fluids, oil, transmission, and filter spares
Epoxy and fiberglass for repairs
Dock lines and spare lines
Equipment manuals

Yes, tools will be included, but i have yet to make an estimate of what i will need. How much do your tools weigh? i am considering not having an outboard but just rowing to and from the anchorage. No scuba, just basic snorkel gear, and i weighed it on my scale. Solar will be included in a revised list. i added 12 lbs each for 4 panels. Thanks for reminding me about spares, fluids, filters, repair materials, manuals and dock lines.

Originally Posted by Anders

We would not be able to go anywhere with only 2600 pounds payload. Just filling up the water and diesel tanks is close to half of that.

Thanks for the feedback. i have started this thread to see if i should consider a CC40 with a 2600lb payload or wait for a CC44 with a 4000 lb payload. They both have 50 gallons of water and 30 gallons of diesel fuel, for 639 lbs weight.

Originally Posted by Cavalier MK2

Couple quick notes. Only use a boat length of chain, make the rest rode.

Electrical is where you can save big in the battery dept. by streamlining your needs. Golf cart batteries?

The windsurfer weight seems high check the figures, they are also a bit impractical unless they can double as stand up paddle boards for exploring. I'd suggest a couple kayaks instead for weight and space savings as well as more practical exploration craft for the back waters. Add a sail to the dinghy for that and you'll still be ahead of 200 pounds.

The 150' of chain is 50' for each of the three anchors. The rest will be rode as you said, i have yet to include the rode in my weight figures. How can i save on battery weight short of using Lithium? As for golf cart batteries, read Maine Sail's writings. And yes, kayaks are a definite possibility. i just guessed the weight of the windsurfer, as i dont want to get it down from the ceiling of the garage right now. A sail for the dinghy is a very real possibility especially if the dinghy i get has a centerboard, otherwise i guess i could add leeboards

[captlloyd]

Originally Posted by longjonsilver

Thanks everybody for your input. This really makes my decision easier!



i have an email in to John Marples asking him what equipment is included in his "dry" weight.



Yes, tools will be included, but i have yet to make an estimate of what i will need. How much do your tools weigh? i am considering not having an outboard but just rowing to and from the anchorage. No scuba, just basic snorkel gear, and i weighed it on my scale. Solar will be included in a revised list. i added 12 lbs each for 4 panels. Thanks for reminding me about spares, fluids, filters, repair materials, manuals and dock lines.



Thanks for the feedback. i have started this thread to see if i should consider a CC40 with a 2600lb payload or wait for a CC44 with a 4000 lb payload. They both have 50 gallons of water and 30 gallons of diesel fuel, for 639 lbs weight.



The 150' of chain is 50' for each of the three anchors. The rest will be rode as you said, i have yet to include the rode in my weight figures. How can i save on battery weight short of using Lithium? As for golf cart batteries, read Maine Sail's writings. And yes, kayaks are a definite possibility. i just guessed the weight of the windsurfer, as i dont want to get it down from the ceiling of the garage right now. A sail for the dinghy is a very real possibility especially if the dinghy i get has a centerboard, otherwise i guess i could add leeboards

I wouldn’t think you would need three separate chains.

[Paul L]

Originally Posted by captlloyd

I wouldn’t think you would need three separate chains.

I agree, they'd be much better off putting more chain on the primary and less on the 2nd/3rd if weight is the issue.

[Cavalier MK2]

At 40' of boat a boat length of chain on 3 anchors is 120'. And I'd make it only about 10-15' on one for easier kedging and use the 5/16" chain size for the 40.

[Mike Banks]

Just go ahead and oput everything you need aboard.

You can then discard those things you discover you do not need. I put all sorts of things aboard my trimaran--and it still out-sailed most monos. The important thing is to have ESSENTIAL equipment where it is easily retrieved or operated. It ios amazing just how much junk you need on a cruising boat, Fenders, warps, dan buoys, life-rings, outboards,

Just go ahead and stash the lot. Keep the heavy anchors too. You will sleep better when that anchor-watch alarm stays off.

Most cruising boats are designed to take a good load. Avoid buying racing or a high-performance trimaran and trying to turn it into a cruising tri. It will be cramped, low in the water and probably slower than a beamier tri with substantial storage in the amas.

Before you build a trimaran, think about resale value. A Tri uses about the same materials as a cat--but will be harder to sell and in some places almost impossible to insure--in Australia anyway. Trimarans of any size need diesel inboard engines--a substantial cat can use twin outboards--which makes them far easier to maneuver, and easier to repair. I loved my trimaran--nothing sails more sweetly than a well designed trimaran, but next time it will be fibreglass and will be a cat.
.

[Anders]

I would ditch the 3rd anchor completely and only use a short chain on the kedge.