Mark44
Katie's Boss
- Location
- 100% one place
I believe the us coast guard site has the flotation formulas online.
The calculations are tedious but not difficult.
Mark44
The calculations are tedious but not difficult.
Mark44
SJ build - removing bulkhead entirely?
- Thread starter SuperJETT
- Start date
1 cu ft of water weighs ~64 lbs, so if my ski ends up weighing 300, then if I displace 5 cu ft with the hull/engine/foam/turf/etc it will be slightly positively buoyant and will float.
In a normal foamed ski, there is around 3 cu ft of foam under the tray.
In a normal foamed ski, there is around 3 cu ft of foam under the tray.
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
So if there is 3 cubic feet that means an additional 192lbs plus you have to know the amount of water displacement for the complete engine and hood area as it will be filled with water also,I know my SX would barely float when full of water,nothing sticking up but the ride plate,after cutting the gunwhales off the ski and losing that amount of foam I don't think it will float as is when full of water.In comparison the SX weighs 250 lbs dry,that floatation test was with the heavy handlepole removed as well as the fire ext holder and brackets ,waterbox and rubber mount were replaced with a PJS waterbox and I was running a 550 gas tank that holds 3 gallons and a very small sealed battery .You might want to consider foaming the inside of the handlepole also.
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madscientist
chilling with these guys.
- Location
- good old p'cola
you need to support the water lines as well. they will/can break from vibration w/ there being only the 1 point of thru hull. 2 points of mounting will eliminate the stress of this effect.
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Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
You could run all rubber hose from the pump housing area all the way up, nothing to have to support.
?
Just a 3" piece of tubing through the hull, hose on both sides of it.
Think outside the box with me man!
I think you're missing the point of displacement/buoyancy.
I'll do some actual calculations and see how I feel about it.
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
Nope just considering all the variables in the equation,I know my SX is lighter than a Superjet,it has at least as much floatation foam,it barely floats,now you take away over half of the foam and add more weight and you have now exceeded your floatation parameters.I will be foaming the large pockets in my new hood as well as the nose section to replace the foam I took out,minimal weight gain maximun floatation gain!
Mark44
Katie's Boss
- Location
- 100% one place
I believe Darin's point was this: There is no need to "know the amount of water displacement for the complete engine and hood area as it will be filled with water also".
Water doesn't add weight in a bouyancy calculation - it's neutral.
All you need is total weight of the vessel, and volume of water displaced by the flotation material. (Foam in this case).
Volume in the engine bay is irrelevant.
Mark44
Katie's Boss
- Location
- 100% one place
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
Okay point taken and recognized as being correct ,let me throw another monkey wrench in the machinery though.There is a safety factor also to be considered,the ski should be able to not only float itself but also safely float the rider if something was to happen.Now I realize that all of you are wearing only USCG approved life jackets right? I am also sure that all of you never ride alone either right? It that is truly your case then no worries,if the answer to either of those two questions was no ,there might be a problem there.Just something to consider.
The only torque the bulkhead sees is what is created by the drag of the intermediate bearing/seals which is fairly minimal.
Mark44
Katie's Boss
- Location
- 100% one place
p
Also if you sink in shark infested waters you may want to stand up on the hull as to keep the sharks at bay. J/K :smile:
Mark44
Also if you sink in shark infested waters you may want to stand up on the hull as to keep the sharks at bay. J/K :smile:
Mark44
Endo
Non-tree hugger
- Location
- Northeastern Indiana
Yep
X2
And as long as the foam is dry....and density of foam plays a small part to the equation.
Mark44
Katie's Boss
- Location
- 100% one place
WFO Speedracer
A lifetime ban is like a lifetime warranty !
- Location
- Alabama
I am not just posting to be a azz here,on my Thunderjet build I am considering doing pretty much the same thing but I will be leaving the bulkhead as is,the halves were foamed seperatly and then put together,so far I have seen Kayak floatation bags posted,just looking for ideas just like Jett and making sure I have all my bases covered before I seal up the two halves for good.I will be doing everything that I suggested earlier before that happens.:argue:
I am glad I went with foam that doesn't absorb water, party for the reason you mention.
Mark44
Katie's Boss
- Location
- 100% one place
o
Just kidding its a J/K........ :biggrin: I am in a funny mood today. :biggrin:
Mark44
Just kidding its a J/K........ :biggrin: I am in a funny mood today. :biggrin:
Mark44
Mark44
Katie's Boss
- Location
- 100% one place
Hollow balls from McMaster carr they are used to stop evaporation in open top tanks come in all sizes.
Mark44
Mark44