Making a raft

>>1052922
If you make it wider than it is tall it'll be incredibly hard to tip over.

A keel will do nothing unless it's counter weighted which will reduce the buoyancy overall.

>>1052948
How would a counter weight work for a keel? A mast? Also why do you need that?

>>1052948
I have no option to make it wider, at least not to the extent that it will be stable relative to its centre of gravity; therefore a keel is imperative.
And doesn't a keel, by definition, include a weight? either way I intend to use one as marked in my sketch.

>>1052922
What kind of structure are we talking about? A diving tower? A roofed shed? Unless we know what forces the raft will be subject to, there's no telling what design is optimal for your purpose.

That being said, look into how center of load/center of gravity/buoyancy center etc work for ships. Might give you enough data to do your own calculations.

I imagine that if you attach two sheets of plywood to "v"-blocks and attach weights to the bottom of the V and rocks inside it, you get the dual effect of a counterweight and a fin that slows down motion in the direction perpendicular to its main plane.

But really, the only truly safe option if you can't increase the area of the raft is to moor it to a weight on the bottom of the lake/shore you have the raft at.

>>1052977
>>1052991

A keel isn't really meant for stability though. It helps a ship go straight through the water rather than sliding.

Same as ice skates vs shoes.

It doesn't do a whole lot to keep a ship upright.

See

>>1052991

>>1053013
>A keel doesn't do a whole lot to keep a ship upright.
Guess you won't mind me removing that 400+ lb lead fin under your sailboat, then?

>>1053024
Sailboats have high center of gravity due to the sails. Rafts without sails have lower center of gravity. Keel won't do crap for that application but get hung up on weeds.

>>1052922
not 2

>>1052922
No matter what you're putting on top. Option 1 is the best; the greater your vessel's angle, the bigger the momentum in this scenario.

If you hang weight on a rope, it will do less when it's needed more.

>>1053054
I seriously don't see how you can say that and still think you're proving me wrong. Sailboats with or without finned keels have fucking keels. Almost all small ships have weighted keels. Without them, or a catamaran hull or similar, they fall over or can only use smaller area sails. Large ships use ballast tanks to regulate center of gravity.

Keel is the name of the bottom part of a boat, whether you think you know hydrodynamics or not.

>t.nautical scientist.

>>1053136
>nautical scientist

Why is it I don't believe you?

A keel on a sailboat counter acts the force of the wind pushing on the sail, well above the boat. So yes, you're right about that.

However OP isn't building a fucking sailboat.

>>1053231
How is it relevant what force you try to counter? OP wants to lower the center of mass to increase the stability of his makeshift barge. A weighted keel does just that.

>>1053237
He should just make it wider.

OP checking in here.

After reading your replies, and /sci/'s replies, and consulting a much more experienced skipper friend, I've decided to widen the base.

Current plan:
2.1*2.1m square base, structure will stand about 1.75m tall, a buoy will be tied to each of the 4 corners.

I just really want to know what this is going to be used for. Don't leave me hangin.

File: HumanBallast.jpg (266KB, 680x453px) Image search: [Google]

266KB, 680x453px

>>1053072
good answer

>>1053365
best plan

how to stabilise a small sailboat?
human ballast to windward!
pic related

>>1053054

>>1053382
Lol, nice troll.

That's for racing or really small boats. Balancing the boat with "human ballast" is a technique with larger (24-40 ft) boats too, but hardly hanging off the side.

File: 13151910_10153494233126003_3685072312740160265_n.jpg (72KB, 641x960px) Image search: [Google]

72KB, 641x960px

Thanks for all info, discussion and assistance, everybody.

>>1053378
It's for an Effigy at a burn event*.

*a regional burning man event we are holding at sea!

>>1053448
Oh, well in that case, a "keel stick" with a sack of bricks works just fine.

Post pics here of the thing before during and after burning! :D

>>1053491
i doubt the thread will still be alive by the time i get back to data access...but i do wish i could share it with anyone who helped heheh..

>>1053496
if it isn't just post >>1053448 that pic and say you're the raft guy. We're not that many, and a lot of us are regulars. :)

>>1053498
fair enough! i'll leave this window open while flying away and hope my computer is on when i get back XD

>>1053500
Look into "settings" in the bottom right of your 4chan window. You can subscribe to threads and change your user experience to the better.

>>1053394

To go further off-topic; your comment isn't entirely true. With small boats it is needed to stay upright, with bigger vessels however, it's only to get a better windflow into the sails.

>>1053686
What, balancing the boat? Windflow is one thing, hydrodynamics is another. The boat has less resistance when not leaning too much, so leaning works two-fold.

>>1052922
Number 1.

Numbers 2 and 3 don't apply righting force to the platform. The weight hanging down can't apply torque to the platform.

Also, in waves, the up and down motion of the platform will repeatedly jerk the cables to the weight and will have to be sized for the load.