Average Human Weight, Safe Excess Weight, &c.

[Free Pirate]

What is the standard weight for a person when designing a small craft? How many extra pounds of displacement, if any, should be allowed for safety?

I expect there to be 8 people on the craft I'm designing, and each of them will probably have a bottle of water or two and some food, maybe some rods and tackle.

Boat weight + (average weight of human)*(amount of people) + safety weight(?) + expected cargo weight = displaced weight at DWL (or at least what the DWL is supposed to displace)

Am I forgetting anything in the formula? Adding anything extra?

Thanks in advance for any advice.

[Raggi_Thor]

I think 80kg + 20kg for supplies (food, water, extra clothing) is "normal".
Then maybe americans are larger that norwegians :-) and drink more beer :-)

[Skippy]

Between a 180lb man and a 120lb woman, you have a 300lb couple, or 150lb per person. I think I figured I eat about 1% of my bodyweight in food per day. Especially in a mono, you'll get the extra flotation automatically by providing adequate freeboard and/or cabin space.

[Free Pirate]

Does anyone agree/disagree with Raggi_Thor and Skippy? I think 20 kg is a lot per person of food and water for a little weekend daysailor. Around 100 kg or 150 lbs a person seems about right. I'd like more opinions about this, since it's a pretty important factor on a little 8-person boat.

Since I could find out the weight of the crew almost exactly (since I know who'll be in it and could just ask them), would that the best way of going about it, also adding 2 kg of DWL mass displacement to that for water and food?

Is it better to be a few pounds over or under the DWL's mass displacement?
If you put one person in a v-bottomed rowboat designed for 8 people, how will it affect stablility, speed, and the factors I'm forgetting about?
What about putting in four people?

I'm trying to figure out the best way of going about finding out how much my boat should displace at the DWL, and where to put the waterline. (Also, how to shape the wetted surface.)

(Is there a better term for DWL mass displacement? Like designed mass displacement, something like that?)

[D'ARTOIS]

Are you from France?

If not - Skippy's answer is definately correct for US standards, for European standards you may count on Raggi Thor's reply.

Every designer has his own idea about weight people are bringing on a floating surface - whatever it will be. You must include not only food, but also weight for
water/cooking/washing up/ etc.

From my last boat, I needed a truck to load my stuff.

[icetreader]

Try this: http://www.halls.md/chart/height-weight.htm
Yoav

[DaveB]

Not sure, as just gettin' started in all of this, but I think a big thing to keep in mind is reserve buoyancy... With small boats you need a lot! Dynamics, people movin' around etc... think for 20' or less you wanna be able to float 3x whatever load you design for... Stability comes into this too of course... Nice for two people to be able to stand on one side of the boat without scarin' everyone else... Again.. just startin' out n' not too sure...

Of course it's key to establish the actual payload too.. I heard that 75kg is pretty conservative... add 10lbs of gear each, depending on the intended purpose n' you should have a reasonable number... This doesn't include vessel outfit (bailers, paddles etc...)

If you've got cad drawings I can do some rough stability calcs for you...
(messenge me if interested)

Cheers,

Dave

[ABoatGuy]

Std people in the ISO world weigh 75kgs. Used by ISO for stability calcs etc. I have no idea where they came up with it.

[Thunderhead19]

Design for 250lb man and 300lb woman.

[asathor]

In Minnesota fishing requires 2 rods and 2 tackle boxes and a 12pack per person, some chips, night crawlers and leaches and a frying pan, a stove, a cooler with ice, coffee, more chips and maybe some bean dip if it is getting late, a little brandy for the coffee if it is cold out, a TV if "the game" is on, a fish finder, a trolling motor, 2 batteries, life jackets, something to sit on, boots that you won't be needing and so on.

My vote is in line with Thunderhead 250-300 pounds per person

PLUS all the usual housekeeping/boatkeeping stuff: Bilgepump, bucket for bailing, bucket for puking, portapotti/wastewater, towels, kleenex, matches ................. I'd say 500 pounds over a bare boat for recreational/cruising use.

The highway scale never lies.

[mackid068]

When we use american weights for Persons alone, I'd estimate 170 lbs for a male and 150 for a female. This is just because over 50% of americans are obese. In regards to "stuff," I'd say about 40 lbs. per person (foodstuffs, clothes, PFDs)

[Skippy]

mackid068: I'd estimate ... 150 for a female. This is just because over 50% of americans are obese.

Just don't say that in mixed company.

[grob]

Remember that if you are designing a sailing catamaran the numbers you choose should be per hull, not for the entire boat.

Also dynamic stability is very important to stop pitchpolling

Gareth
www.fourhulls.com