2016 Surf bags

[DrPorter]

I took out my stock surf bags to compare them with the wake 9 custom bags I bought for my 2014 z3. As you can see in the photos the difference in the bags is minimal when comparing both Port bags. When comparing the starboard bags there is NO difference (photo not included). That being said I have a set of custom Wake 9 bags for sale that will work on a 2014 and up Z3 and probably even a Z1. I paid $1350 for the set plus shipping and fittings. They are for sale for $1000.
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[BJM]

Did your wake 9 bags push the side seats up at all on the Z3? How close were they to the top hatch in the rear compartment?

[DrPorter]

Did your wake 9 bags push the side seats up at all on the Z3? How close were they to the top hatch in the rear compartment?

They fit perfect. No they did not push the top seats up and they were 2-3" below the hatch in the rear

[Germaine Marine]

If the wake 9 bags are 1300+ per side then that is a difference of 400+ total in the rear. Thats a ton....

[Germaine Marine]

Dr Porter I would love the bags. So Im calling first Dibs

[DrPorter]

If the wake 9 bags are 1300+ per side then that is a difference of 400+ total in the rear. Thats a ton....

I'm just saying that either Tige under states the weight or wake 9 overstated because there is no way the difference is 400+ lbs

[ragboy]

2 things...

1. We tested over and over, went though 3-4 sets until we got bags that DID NOT push up on the seats because that drives me crazy.
2. We based our weights on testing using consistent pumps over time. Testing with known sizes and pump speeds and doing it several times. Our testing was done with the bag IN the boat, which makes a lot of difference.

The 2015 Surf XL bags for the Z3 were based on our 2014 bags, but made a bit smaller on the port side. So they basically took the starboard side 2014 wake9 bag and put it on both sides for the 2015 Z3 with Surf XL.

I believe there have been a couple of changes in 2016, so I can't really answer that.

[Dandy]

If the wake 9 bags are 1300+ per side then that is a difference of 400+ total in the rear. Thats a ton....

Nope, 400 lbs is actually 20% of a ton ha ha ha ha

[chpthril]

I'm just saying that either Tige under states the weight or wake 9 overstated because there is no way the difference is 400+ lbs

based on the 2015 surf xl art work PDF I got from tige, the bag is spec'ing out about 950.

[Dandy]

based on the 2015 surf xl art work PDF I got from tige, the bag is spec'ing out about 950.

It sounds like ragboy calculate based upon fill times and you are calculating by volume.

I would say that volume calculations are going to be more accurate.
(Volume (Cubic Feet) X 7.48 (Gallons Per Cubic Feet) ) X 8.3 lbs per gallon of water = total lbs

By using pumps and times, the output of the pump can easily change based upon any head pressure that it needs to pump against or how the pump is being "flooded". If ragboy's calculations seem high, they very well could be as the pump volume will most likely decrease over time as the bag fills, due to head pressure and change of pressure in the "vessel" that it is pumping into.

Not taking sides, but my thought is calculating by volume would be better than pump run time. The only way using a pump system would be accurate is if there was a flowmeter in the line to calculate how many gallons were pumped in to fill and then multiply by 8.3 lbs per gallon.

So, to me the ultimate way to measure the volume in a boat would be to place a flowmeter in the line. There is also potential that the bag will not be able to fill to the same volumetric area due to the confines of the boat's structure (think Z1 bow sac) that it would in an open environment.

It's Fun With Numbers Monday

[UNSTUCK]

Definitely a bad idea to base weight on time. Everything that Dandy stated, plus you are also assuming that the pump does not lose any of its duty cycle. Also, every pump is rated for x GPH at a specific regulated voltage, or should be anyways. Any variation in voltage will speed up or slow down the pump.

Flow meter would work, but I think I would just put the boat on a scale.

[ragboy]

No, that is not correct. You can take the artwork and base on volume. First of all, look at the artwork its shows rectangles. Then look at those pictures of the bags filled up with air, they are not even close to rectangles.

One of the first tests we did was fill up bags out of a boat and on the ground. they can hold much more water than the VOLUME calculations of rectangles calculate to.

The best way to measure, is to use a flow meter and measure exactly what you put in WITH THE BAG INSTALLED. Another way is to use a pump in the boat and timing filling bags that carry a KNOWN capacity, like a 750 or 1100 in a controlled place where you can monitor that the pump is fully primed and using the same setup, etc.

I think I even did a video way back in 2010 where we did just that, I would have to find it. We also showed the pictures of the bags being filled on the ground, and in the boat, etc.

Our first tests were backed up by values given to us from Wakemakers a long time ago.

That all said, when we did these bags in 2014 they were to replace the small 550 or so bags in the corners. It was clear and obvious that my bags held MUCH more, and I was never selling a WEIGHT, I was selling a WAKE. I always made sure that I rounded UP on everything because from my standpoint, people were worried about TOO MUCH weight. So if I rounded up a bit, I wouldn't get in trouble that way. At least, at that time, that was the prevailing concern. So if I said these bags would do about 3000 lbs of total ballast in your boat and you installed and if it turned out it was only 2800, you would be fine, as long as the wake was what I showed. And as far as I know it always was, because we always filmed with the same bags that we sold.

Now I am not speaking for any boat manuf., but you could possibly see that they may have reasons to round the other way.

[chpthril]

First let me say that we all know that running changes can and have been made. Those early specs could have been with the 250# in floor tank was still part of the 2015 build. The dimensions may have been adjusted when they dropped the tanks. Looking at the pics above, I see maybe a 100 lbs difference in the port side sacs.

As to calculating dimensions. Unless the sac is grossly undersized as to the locker dimensions, we will not see the same bulging as seen with those sacs out of the boat filled with air. So, this brings us back down to the volume capacity based on rectangles, being reasonably close.

As to using a pump with a known capacity for a time based sac capacity. If those calculations were used with aerator ballast pumps, everything known, is incorrect. First, as noted above, you have to a constant and regulated voltage supply. Any pump will have a different flow rate between engine off 12.5 and dropping, and engine running 13.5 and fluctuating. You would have to regulate the supply at the same voltage as the manufacturer used in their testing. if not, your results will be incorrect. 2nd, you have to factor for head pressure. This is a combination of hose length, hose elevation and fitting restriction. We all know how the sac fittings effect flow rate, right? Those results are around here somewhere. We can see up to a 25% reduction in flow rate from the peak rating to what we actually get at the sac. This could result in over calculating the sacs capacity, as it is taking longer to fill then the flow rate used in our equation.

If the time based calculations were factored using an impeller pump, they may be closer. Impeller pumps are less susceptible to head pressure, but still effected. Again, your supply voltage has to be regulated. Engine running or running the pump off a static battery, is not regulated. Further, for testing, you would want to fill through the top of the sac, rather than the bottom. Filling through the bottom as we do with a typical ballast install, will have increasing head pressure as the sac fills with water. In other words, your starting flow rate will be faster than the ending flow rate. Not a huge difference, but a difference none the less that will skew the test results.

In the end, its very hard to and not practical to, get an exact measurement on a sac. Especially, when you have a dozen different custom sacs for different boats. We estimate the capacity as best we can and hope the customer sees the results.

[ragboy]

First, using a pump or even better a flow meter with the bag INSTALLED is by far the only way.

Yes, it is true that the bags are confined, and that moves it back, but there are many more issues.

1. There is the divider like triangle that divides the lockers from the long arm on most of the boats at least before 2015. This triable crimped the sac at that spot.
2. You can make a rentangle for that rear locker, and assume it will fill, but it may not. The height has a big impact. And as the height grows, you have to seriously reinforce the walls of those lockers because they want to blow out bad.
3. Venting can occur before the sac is filled all the way, and then even more more when listed.

The only way to accurately measure water weight in the bags is to fill them in the boat installed and if listed, in the water. This is why weighing on the trailer on a scale isn't even as accurate.

The flow meter is best, and an aerator pump that you have "calibrated" and with the engine running at idle works well, just not perfectly.

As an example, the custom bags for the 2015 Z3 were a b*tch and there is a reason I never tried to make those to sell. Wakemakers has asked me about it, but it requires SERIOUS reinforcement back there. Since the hard tank is removed, the bags fall lower and so they have lots of room above. I had to try a couple of times to get the height right, and then had to adjust the inner size much smaller to prevent the boat from exploding. Haha, it wasn't that bad, but we were popping stuff back there all the time. I finally got it right and Tige helped me reinforce the walls thoroughly.

Rob Harrington has the only set and that wake on that Z3 is a thing of beauty. Had to go through 3 sets of bags if I remember, and a crap load of fittings. Not to mention the 2 prototype ballast king pumps for cross over. Man, that was a great boat, glad to know its still "in the family" so to speak.

[Germaine Marine]

So what's the story then rag on exactly what those rears are vs what's in the 16s like pictured above....

I'm still looking for the answer...