- Location
- California
How deep do skis sink?
- Thread starter DylanS
- Start date
- Location
- Fort Worth, Texas
I wanted to chime in on this to let people know about the buoyancy needed for skis like this... This is an example...
My helium when I added in all the materials used and approx weights and density of each one in the build gave me an amount of foam needed to be neutral... not float, but just below surface be neutral. I needed approx 2.25-2.5 cuft. of foam. Now, that doesn't seem like a lot of foam. but really it is. a 5 gallon bucket is .67 cuft. so i needed 3 1/2 buckets of foam to be neutral..... That's a LOT of foam. I foamed the gunwells down to with-in 1" of the bottom so water could flow under, I foamed the nose all the way up to the pipe, and I foamed the complete hood except for a vent area for air to the engine. It came to approx 2 cu.ft. so, by my calculations, that ski if it filled up and the tank was closer to empty would be between neutral and 10# under the surface which for me was fine, i can hold 10lbs at the surface... and if there were any extra trapped air pockets, it would be even better. so foaming a tray generally isn't going to keep it from sinking, foam the nose, and hood if you can, and running thicker turf will help also....
My helium when I added in all the materials used and approx weights and density of each one in the build gave me an amount of foam needed to be neutral... not float, but just below surface be neutral. I needed approx 2.25-2.5 cuft. of foam. Now, that doesn't seem like a lot of foam. but really it is. a 5 gallon bucket is .67 cuft. so i needed 3 1/2 buckets of foam to be neutral..... That's a LOT of foam. I foamed the gunwells down to with-in 1" of the bottom so water could flow under, I foamed the nose all the way up to the pipe, and I foamed the complete hood except for a vent area for air to the engine. It came to approx 2 cu.ft. so, by my calculations, that ski if it filled up and the tank was closer to empty would be between neutral and 10# under the surface which for me was fine, i can hold 10lbs at the surface... and if there were any extra trapped air pockets, it would be even better. so foaming a tray generally isn't going to keep it from sinking, foam the nose, and hood if you can, and running thicker turf will help also....
Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
Errrr, Ski Sunk, not stolen.We all know that the person that claims the reward is clearly the person that stole it.
- Location
- California
I know, just was being a smartass about the reward suggestion.
Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
I'm just being a smartass in general because everybody here at work is on my last nerve. (Here being anyone work related).
Krenn the way I figured : 1 cuft. h2o =7.48 gal, h2o=8.33#'s per gal. 7.48 x 8.33= 62.3 #'s per cuft. 2.5cuft x 62.3#'s=155.75#'s. if ski weighs 250 aren't you still 95#'s positive ?
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An easier way to visualize it, look at your ski when it's floating. The volume below the waterline is the amount of volume needed to float it. Look at that volume compared to the entire volume of the ski, and you quickly see it is going to be really tough or impossible to find anywhere near that much volume in a freestyle ski to use for floatation.
Freakrider
X247
- Location
- Tampa Bay area
Superglue one shut lol.
Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
Or silicone.
DylanS
Gorilla Smasher
- Location
- Lebanon Pa
I had a 1000 or 1500 dollar reward out for anyone to just LOCATE it not even Dive lol
Neutral flotation scares me if the ski gets away from you.lf you can hold on to it great.But l have been preaching this not adding flotation thing for years.Mostly building smaller afternarket skis,there just isn’t enough areas to put flotation unless you @McDog it.Pool noodles everywhere!
l would rather let that bitch sink straight down.But in some cases like Dylan’s it is not such a good idea.lt’s just a risk we all take with a a/m ski.
Let the debate and math formula carry on.
SXIPro
JM781 Big Bore
- Location
- Here on the 'X' mostly
I'm sitting here with my ski cut open in the cellar and after all this math wondering if I should just say "phuck it" and not even bother loading it with pink sheet foam and just button it up tight and hope the trapped air keeps it at least as 'bouyancy neutral' as it would have been with the pink sheet foam. Ski is sealed really well, and no scuppers.
Of course if something catastrophic happened to the hull I'd be screwed...
Of course if something catastrophic happened to the hull I'd be screwed...
Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
Put the Pink Foam in there................. Its one of those "It cannot hurt to have done it".
SXIPro
JM781 Big Bore
- Location
- Here on the 'X' mostly
yeah, I will. Plus it's fun using the hot knife, and smells wonderful.
- Location
- California
The other thing to consider with all this flotation and neutral buoyancy math is that depending on how deep the area your ride in is that your floatation and buoyancy is dependent on air, either trapped or in the foam and air compresses. So at the surface if you are just neutrally buoyant once it goes under the air will start to compress and you are now negatively buoyant and the deeper it goes the worse it will get. This is why divers use BCD vests to add air as they go deeper to stay neutral and let air out as the rise and the air starts to expand.
I'm sure someone here that is smarter than me can make an inflatable bladder and air tank that is depth sensitive to like 15' that would go off, inflate and bring the ski to the surface.
I'm sure someone here that is smarter than me can make an inflatable bladder and air tank that is depth sensitive to like 15' that would go off, inflate and bring the ski to the surface.
That is a really good idea.
Quinc
Buy a Superjet
- Location
- California
Foam it then shove pool noodles or shave foam to fit along the sides of the engine bay like the stock hull has. As well as putting as much foam in the nose as you can. If it buys you another 5 minutes of float time that might be the difference of getting a tow rope on it or not.