Oversized underfilled ballast bags - ok?

Hi, trying to decide between ordering expensive custom bags, or affordable "off the shelf" bags:

Say I have a reinforced space that's 19x19x42, and I can get a good deal on a 20x20x50 bag.

Is there any downside to using the oversized bag underfilled in the space?

Thanks! Keith

yes they can put too much pressure on the surrounding walls (possibly doing damage)where the bag itself would have otherwise supported the weight

If the space is reinforced enough to take the pressure of the water pressing against it (same amount of pressure as if you filled the space with just water), you should be OK, but there is one thing you should be VERY careful about if you go for it. If the bag is not rigged up to automatically overflow when filled to the point where it takes up the available space, if you forget to shut off the fill pump at the proper time, the bag will act like a giant hydraulic ram and can exert enough pressure to break things up. So you either need an overflow system, a pop-off pressure valve (like the pop-off on a turbocharged car to keep it from overboosting), or iron discipline to make sure you shut it off on time.

if they're so full that they hold their shape, and if there's enough room, they could roll around. this is much worse.

the confined rigid space issue is very real, but i think the only way the size of the sack could help you there is if it was small enough to rupture before it caused damage.

Its really not a big deal if it can take the pressure, it should not mess up the sac as long as the area around is smooth. but i have had 550lbs sacks in an area for a 375 its no big deal. save the money and get the bigger ones

Thanks for the replies! These are for the rear of an SSV if that helps?

I would get the gravity games bags for the boat. You should be able to get them through your dealer or call Fly High direct. I believe those are made to fit that space exactly. They are a little expensive but I think it would be worth it. In your case I wouldn't worry about the extra inch on the width and height, but I think the extra 8 inches on length will give you some problems when trying to fill them. I would guess the bag will get bunched up and be a real pain to fill. Either sac you go with if you are automating it definetly put in a overflow. I just installed a gravity games front sac in my friends boat and put a over flow in it, it worked great.

Keith,

I had the same delima with my SSV. I saw the GG sacs for the rear which are supposed to be 800 lbs each. There is no way those things fit in the rear compartment of an SSV without touching the walls of the compartment. I also can't see how they could possibly fully expand.

Being nervous about damaging my compartment as you are, I opted for Fly High's Pro X series V-drive sacs. They weigh 400 lbs each and fit nicely in my compartment. However, if I had to do it over again (and I may) I would go with Fly High's Pro X 750 lb sac in each compartment. I want a little bigger wake than the 400 lb sacs can produce. I think the 750 lb sacs would do the job. Basically you are talking a difference of 2 inches. The 750 lb sac is 50" long and the compartment is 48" (if you remove the dummy wall on the driver's side).

I wouldn't worry about the pressure because the SSV has a pressure release. When the sac reachs full pressure the water spits out the drain. With my sacs water starts spitting out the drain before the sacs are at their maximum capacity. Therefore, I would be fairly certain that water would spit out the drain before any damage is done to the compartment. If the water didn't have any place to go it would be a different story, but with the SSV that's not the case. The water has a place to go. If it was a problem Supra dealers wouldn't be selling GG bags to go in their boats.

I think the 750 lb sacs from Fly High are the way to go. Having the 400 lb V-drive Pro X sacs in my boat I can say that they are top quality. The fittings are identical to what came stock with your SSV. After all, Fly High makes the GG bags as well. The Pro X sacs are the same, just a little smaller. They are also a lot cheaper at $149 per sac as opposed to the $700 price tag for the complete set of GG bags.

(Message edited by nauty on April 28, 2005)

GG sacs for the rear are only 500-550 lbs each NOT 800.
Front GG sac is 900-1000 lbs.
Total for a SSV GG edition is right around 2000 lbs.

800 lbs per side no way!!!! Think about it. Could you put 95 gallons of water in each side of your engine compartment????

95 gal X 8.4 lbs gall = 798 lbs

According to the 21st edition of The Machinery's Handbook, 1 gallon of watter weighs 8.337 pounds

Thanks again for the replies! Appreciated!

Nauty summed it up exactly - the 20x20x50 bags are sooo much more affordable, and larger, than the "custom" GG rear bags at 19x19x42.

Keith.

E Double U,

Speak with Mike at Fly High (the maker of the GG bags) and he will tell you different. The GG rear sacs will hold 800 lbs each.

I fully agree that the compartment will not hold 800 lbs of water. If you read my post above I make the point pretty clearly that there is no way the compartment of the SSV will let these bags fully expand to their maximum capacity. Therefore, why spend the money for an 800 lb sac that you don't need?

E Double,

Also to clarify, the sacs that come in the rear compartment of the Supra SSV Gravity Games Edition are not the Gravity Games sacs. Supra will not put these sacs in their boats because of liabilty. A Supra dealer however, will sell them to you independently. The GG sacs that I am speaking of (and what I assumed Keith was asking about), are indeed 800 lbs each for the rear compartment. They are the ones that are actually used in the GG competition.

Richard,
Thanks for the clarification.

I was just trying to make the point that it is nearly impossible to fit 95 gallons of water in that space. Like you said those sacs may hold 800 lbs but will not fully fill up.

I do understand that you have to order the GG sacs specifically for the GG edition because the regular sacs come with that boat. I am at the Supra Dealer alot and they have the GG bags there for sale and they are huge!!!

Everybody have a great and safe summer!!!!

Ok, I'm confused:

The rear GG bags sold by BI are 42x19x19:

Using a volume calculator (google it) the above rectangle works out to 8.74 cubic ft.

Multiple the above cubic feet x 7.48 = 65.37 US gallons.

Multiple the above US gallons by 8.337 = 545 lbs.

So that's 545 pounds per rear 42x19x19 SSV GG bag from BI.

Where does the 800 lb figure come from?

That is a very good question. Here is how Mike at Fly High explained it to me when I called asking what the real weight of my stock front sac was in my SSV.....

The dealer says that my stock front sac is a 650 lb sac. I think that thing is huge. I thought there was no way that it could only be 650 lbs when comparing it to a 580 lb Skylon Fat Boy. The Supra sac is much, much larger.

Mike explained that the stated weight of a sac is for the dimensions only. In other words, if the sac never expanded past the seams it would weigh the stated number. I'm sure you've seem how sacs buldge greatly when you fill them up. They buldge far past the seams. If the compartment will allow the sac to buldge it will hold more than the stated weight.

With the example above using my stock 650 lb sac, this sac will actually weigh between 700-800 lbs. However, the compartment that the sac is in may not allow it to expand enough to hold that much weight. Therefore, in regards to the GG scas holding 800 lbs, as we stated in the posts above, it is unlikely that the compartment will allow it to expand to hold that much water (weight). I think it would be safe to assume that these sacs probably are closer to the 545 lb mark when used in the SSV rear compartment.

Sounds good! Thanks Richard!

FYI for the sake of completeness, I spoke to Mike at BI earlier today. He says the GG SSV bags use a thicker material than the Fly High Pro X bags - that's why the GG bags are more expensive.

So I ordered the GG bags.

Thanks! Keith.

Keith,\
How much did you pay for them. I am also looking to get some.
Thanks

I wanted to get the GG sacs, but they were just a bit more than I wanted to pay. My dealer offered a great deal on them (thanks WSDB), but I opted to go another route.

Boarders Paradise will make custom sacs to whatever dimensions you need. I just placed an order for two 19x19x42 sacs with three valves. The total price to my door was $184 for both.

I realize that the GG sacs are much thicker and more durable, but the price I paid was much more appealing. The sacs from BP are the same material as most regular sacs, such as the ones made by Sklon or Launch Pad.

I used these types of sacs in my old boat for years and never had any problems with them. Heck we were crawling all over those too. I figure with these being safely tucked away in compartments they should be alright.

No matter which sacs we choose I'm sure we'll all be happy as long as the wake is BIG.

(Message edited by nauty on May 06, 2005)

Sorry I'm not at liberty to disclose how much I paid - call a BI dealer for a price?

These are replacements for my current 2 year old rear GG bags which have the old style (blue) waterbed fittings. I gave up trying to fix the leaks from the waterbed fittings - which made the carpet wet and mildewy and meant I had to keep drying the area - aaagh!

My new bags on order have the new fittings on them - BI assure me they will not leak!

So I'll be selling my old rear GG bags in the next couple of weeks on the wakeworld classifieds, once I get the new rear bags. I'm thinking $120 for both my old rear GG bags, including all the old waterbed fittings too - any early takers feel free to PM me.

Thanks! Keith

(Message edited by keithf on May 08, 2005)

I have a 16x16x70 700LB BI fat sac for $85 plus shipping if anyone is interested. The sac is new in the box and is gray. It has the new quick connect fittings and is made of Valmex material like the Pro-X Series. Email if interested.

bigwakes@bellsouth.net

Yhea check out Boarders Paradise's custom sacks. I have seen several customer's boats with these and they are sick.