Anybody ever weighed the sacks when full?

Brodie, Ben, and I were having this discussion while riding last nite. I have an 03' X-2 with 900 stock. Then we add the Fly-High sacs as follows.... (weights off website)
370 Tube on the floor in bow
400 V-Drive width-wise in bow on top of Tube
400 on the floor width-wise in back
155 Brick next to the driver
Two more 400 V-Drive sacks (only about half full) in the back storage

So, if they weighed exactly we figured 2500. But the question is, we fill those 400s on the floor and up front super full. Are they 400 if exactly a square(like wedged in a perfect rectangular spot), or does Fly-High account for the bulging when rating? We were thinking about leaving her sacked out and going to a cattle scale. Anyone already done it?

A gallon of water weights 8 lbs.

BRILLIANT David!!! I dont happen to have a meter on the Tsunami pump telling me how many gallons are going in either. Question still applies. lol

The Tsumami either fills at 800 gph or 1200 gph depending upon which one you have. How long does it take to fill the bags.

1200 tsumami: 20 gallons X the amount of time (in minutes) to fill = # of gallons in the bag X 8 lbs = the ballast weight.

So, you start filling and it takes 2.2 minutes to fill. That would be: 20 X 2.2 = 44 gallons of water X 8 lbs = 352 lbs.

Not trying to be an a-hole here but this is simple math.

(Message edited by dabell on October 17, 2008)

Yah, water weight has always been a mystery IMHO. Some people fill those things not even close to full and claim they are running "full". Others fill them until they bulge. When I was talking to a cat from Fly High on the phone about the V-drive sacks he was saying they they would weight more than 400lbs when full if you let them "bulge" out.

I am not too concerned about the actual number of lbs I am running as long as the wake is mackin, but yah I have been curious as well, if you had time in the winter it would be an interesting study. You could almost calculate it (roughly unfortunately), by timing the amount of time it takes to fill one up, taking into account the pump rate, water weight etc. Like if you had a pump that pumped 1100GPH and it took 5 mins to empty most of a sac (I say empty instead of fill that way there is no "head force of pumping against gravity), that would be approx 92 Gallons * 8 lbs = 733lbs. You could also get a couple 5 gallon buckets and measure the amount of water coming out that way. I know this was done to figure out how much weight a wakesetter locker would hold on themalibucrew.com.

Based on their published dimensions, most that I've calculated are very close, but the "L" shaped surf sac is light by about 300# from the stated weight.

doesnt water weight change with temp ? I think it's like 1gal of water weighs 8.34 lbs at 71 deg. F or something like that

^^^ maybe only tenths of a lb every X degrees, good question, dunno.

"A U.S. gallon (determined by fluid volume at 72 deg. F, at sea level) of fresh water weighs exactly 8.3452641 lb"

Quoted from WikiAnswers

(Message edited by lovin_the_wake on October 17, 2008)

"Yah, water weight has always been a mystery IMHO." I agree with you on that

Montgomery, yes water does change with temperature. You are referring to its density. As the temperature increases from 0*C (Canadian terms haha) its total density changes in kilogram per cubic meter. Water is at its heaviest state between 0-5*C, below that the density will decrease, and above that, the density will decrease.

And with the sacs, the mass that they stick on the side of it is a number based on a calculation of the size and volume of the sac itself. Its not as if they filled it and stuf it on a scale and said ...boom, 300 lbs. Its all calculated so you will never be sure to get an exact same amount each fill, will most likely always change.

You guys crack me up. Pumps vary by age, use, hose irregularities(partial kinks), and impellor wear. Brodie's same pump was a good minute slower than mine, same pump. Good info M-Dizzle, the wake was mackin!! Just another one of the random conversations 3 wake-tweakers have on a boat during the 5 hours we all sit 3 feet from each other. Thanks Fellas!!

A gallon of gas in Canada weighs 8 pounds and a gallon of water weighs 10 pounds. Might it be that 'heavy water' the reactor guys are using, or maybe it's just our bigger gallon.

A bit more on topic. My sacs in lockers can't fill to there maximum shape but I bet they get to within 15% of the maximum. One of these days I'll put the trailer on scales before and after I fill the sacs.
I wonder if I should add the weight of the water I spill filling the sacs too?

I Love You Guys

i doubt those pumps really pump at that rate. it's doubtful the manufacturer accounted for whatever vertical height you're lifting the water.

i think you'd be better off filling the sac at home on a hose and using your water meter although you could easily get more accurate.

Or you could go with a 55 gal drum and fill that up a few times by emptying the sacs. The real question is...Can you get the boat on the trailer, off the ramp and to your house safely without: sliding the tow vehicle into the water or breaking something on the trailer.

Timing the pump won't produce an accurate weight. The gph ratings on pumps are maximum flow rates with zero head pressure. Head pressure is how many feet the pump needs to lift the water and the more head, the slower the pump will flow. In our real world applications of filling and emptying ballast, the head is approximately 3-4 ft filling and 2-3 emptying.

Check out this Tsunami bilge pump, which is the identical 1,200 gph pump most of us use. It's flow rate slows to 900 gph when its lifting water to the height of the thru hull.
http://www.premiumpowersports.com/Attwood-Tsunami-Cartridge-Bilge-Pump-T1200-p-258.html

Hence why i asked if anyone has ever WEIGHED THEM!!!!!!!!!! WEIGHED!!!!! I'll let it go, obviously the answer is no. lol

Jarrod if your wondering and want and exact answer. fill a 5 gallon gas can to a certain line on the can. Weight it. Then when you are pumping out a sac pump it into that can, count how many times you fill that can, when it doesn't fill the can all the way up take that partial can home weight it, add that to the number of cans you fill times the full can weight and there you go. IF its that important to you.
I understand what you are saying about the boat conversations we talk about some stupid stuff too.

Does anyone know if I was to drop a filled sac into the water if it would float or sink

I think you would put a serious strain on your trailer if you trailered it loaded with 2500. You are looking at 7000-8000 lbs total weight with the boat, trailer, ballast, and other items. Good luck with it.

Still don't know why you are so upset with the result of your post when several good answers were provided to accomplish what you are looking for.

As far as the weight of water at temp, you are talking about differences like 8.3389 (4 C) vs 8.3453 (room temp) lbs

Kevin, I know it would put a strain, hence I've never done it.

I was just joking, hence the 'lol'. I'm aware of flow rates, etc. It was a question of 'has anyone ever weighed' it, not smart-alec waker comments about how much water weighs.

All in good fun!!

water is most dense and weighs 1000kg/m cubed at 4 degrees celsius. its most dense at 4 degrees celsius otherwise lakes would freeze at 0 degrees celsius from the bottom up and life wouldnt exist.....one of the only things that i remember from my limnology classes in school. who cares how exact your ballast is though, when your friends get on board your boat do you ask them exactly how much they weigh so you can come on wakeworld and tell everyone you were rockin 3,456.789 pounds of ballast on the weekend?

Jarod, a buddy of mine and myself filled the v-drive sacs in the back of his truck and then drained the sac into a 5 gallon bucket. We got 11.5 buckets at 40lbs per bucket, so ya when bulged they hold around 460lbs. I also did this with the integrated bow sac that claims to be 650lbs and i only got around 550 out of it. I run 1 way spring loaded check valves on my over flow lines on the v-drive sacs so they actually bulge before overflow starts, and they stay bulged out. I replaced the hard tanks with these sacs, 05 X2.

Steve seems to have the most scientific approach yet. Thanks, Steve.

For sure pumps are going to work at different rates, as said above. And calculating based on flow time is not going to be accurate at all.

You are going to need to do some serious calculus if you are going to calculate the volume of a bulging bag. A tank on the other hand would be a slam dunk any high school graduate should be able to do.

Sacs float, I have dropped lots in the water! We have a brick on my swim deck that has found it's way off a few times. We just grab it and re-attach. Hope that helps.

M dizzle...pics of your wake are always mackin.

Fill the sacks in the back of the truck, weigh the truck at the dumps.

^^^^^^^that is what I was thinking

I've always just figured the volume of the sacs by their measured dimensions. Fresh water is 62.4 ish pounds per cubic foot, so the calculation should be pretty close if you don't over fill...

i emptied a full rear seat sac bucket by bucket to get the weight cuz i wanted to get the weight for a tank being built to replace it. it was about 800 lbs if i recall and it was filled to the max

so what weighs more? a pound of WATER or a pound of LEAD.

uhhhh doesn't a pound weigh a pound john....?

The real question John is what weighs more when the boat gets swamped? A pound of water or a pound of lead?

lol... nice art. in that situation they both STILL weigh a pound, however, I would rather have 2500 lbs. in fat sacks than in lead.

This is great!!! love the discussion as only a science teacher would!!!

Just take your boat to the local dump once with the sacs empty and once with them full and ask for the weight.