I’ve entered the 2008 Capitola Begonia Festival float parade. I have an idea for a float but am concerned on whether it will work or not. The “barges” supplied by the committee are 8’ x 12’ (three sheets of plywood nailed to a 2x4 frame and floated by “standard” Styrofoam billets). The float can be no taller than 8’ because it has to pass under a bridge. But taller is better in the judges eyes.
Here are photos from last years entries. And here is my idea. The top of the lifeguard tower would be about 7.5’ to 8’ high. A 150 human is proposed to stand on top of it (the tower being situated in the center of the raft).
My question: Will this be stable? The float will be moving slowly (powered by a trolling motor) and there will not be much wave action to contend with. I’m concerned that the design will be top heavy and flip over.
Will what be stable? The tower? Why wouldn’t you firmly attach the tower to the base of the float?
Or are you asking if the entire float stucture is stable? That would depend on the undercarriage structure of the float–presumably it has wheels, yes? Wheelbase and weight distribution are important here.
And what’s “wave action”? Or, wait. Is this a water-bourne parade? If that’s the case, then the floatation structure underneath is what’s important. “‘Standard’ Styrofoam billets” doesn’t mean anything to me, I’m afraid.
The stability doesn’t look dicey to my eye, but a lot depends on the materials. Last year’s floats seem to be lightly constructed, with skins of chicken wire and paper.
From your plasticene rough draft, I’m guessing you have a sea serpent with 2 parts visible. On a stack of rocks or muffins, there’s a person gesturing toward the creature. He’s singing “Beyond The Sea,” perhaps. Or maybe he’s trying to train it. “Jump, Nessie!”
Anyway, only the center pedestal needs to be substantial, to support the man’s weight. Your raft has an 8 ft. beam and a flat bottom, so it won’t be tippy, even with the guy on the pedestal If it’s an actual person, I presume he’ll climb down to duck under the bridge. I’m picturing him running across the bridge, and remounting the float on the other side. :eek: By the way, if there’s a big rain before the parade, the water might rise and reduce the clearance.
An 8 X 12 raft won’t be very boatlike in handling. I’d recommend mounting the trolling motor at the front, and a simple fixed fin at the rear will make a big difference in how well the thing follows the motor, especially with a little cross wind. Stashing a paddle or two somewhere, just in case, is something to consider.
Are there rules about Personal Flotation Devices? Technically, it’s a 12-foot motor boat, even with the dinky electric motor. Find out what you need to have aboard. Probably, just having one PFD per person is enough, and they needn’t be worn. Find out.
Yes, it’s water borne as the linked photos show. I don’t anymore about the Styrofoam billets, standard is all they provided. Sorry. The barges are provided and must be used.
Yes, I can firmly attach the tower. I guess what I was asking about is is there a way to calculate how far off of center could the whole affair lean before tipping was eminent. Eight foot wide float, tower in center, 150 pound person 8’ up in the air. These are all the exact specs I have. But I don’t need answers down to the millimeter, just a back of the envelope calculation as to whether this float would be reasonably tip worthy.
More or less you’d need to calculate the approximate center of gravity which would depend on what materials you’d use. Lighter materials would mean a CoG closer to the ground. Then determine if it’s possible for that center of gravity to shift or sway beyond the base (wheelbase?). That’s when tipping would occur. Heavier the base, the lower the CoG, and the less likely the CoG will extend over the support base and result in tipping. Having a heavy frame and most of the weight near the floor is what keeps double-decker buses stable.
EDIT: :smack: Just realized this will be a float-float and not a parade float. I doubt my post will help any.
How much does the standard platform weigh? How thick is it? Personally, I’d be hesitant enough about calculations to build a model. Scale the weights and the sizes, float it in a bathtub, then poke at it to see how hard it is to tip. I wouldn’t scale the whole design, just the base, tower, and human weight at the top.
Seriously, I’d want to see the model taking waves and righting itself after you gave the human on top a shove.
Probably your best bet is to just do a dry test. Move the platform into an open yard and mount the chair to it. Put 200# of ballast or friend on top. Have four or five strong type guys grab one edge of the platform and lift until either you’re satisfied that it will be stable or it demonstrates that it won’t be.
You can also place weights on the corners to bring the center of gravity down.
You need to construct it in such a way that tipping it tends to submerge more of your buoyancy volume - which will then generate the upthrust to right it - the trouble is that a high centre of mass like you have will tend to lift the other side up.
There’s a righting moment calculator on this web page that I think can be adapted to your needs - it’s designed for boats, but treat it as box hull and put the CG high and see what happens…