Removing floatation

SURV1969 · Post by **SURV1969** » Tue Apr 01, 2008 8:17 pm

Does anyone know if the ballast is flooded or not?

Terry · Post by **Terry** » Wed Apr 02, 2008 7:54 am

It does not look like the floatation in the cabin top beside the daggerboard starboard above mirror is contributing to anything in the sinking demo, it is above the water line. I was also thinking of using that space for stereo and other electronics. There is really not much up there as I have had it out to install deck hardware then put it all back in (a whole bunch of small pieces) why...I don't know, should have left it out. Next time I will leave it out, it is a nice spot for other stuff.
I like the big air bag idea, a couple of them could be used under the aft berth as that is useless for storage anyway. Self inflating co2 would be the way to go.

Trouts Dream · Post by **Trouts Dream** » Wed Apr 02, 2008 8:09 am

Got me thinking

On my X I don't use the area under the panels in the rear berth for storage. Long tubes filled with air would displace water in the bilge forcing it into my view before there is enough to cause problems and giving extra flotation.

Great idea guys, thanks

Catigale · Post by **Catigale** » Wed Apr 02, 2008 9:49 am

Has anyone SWAGGED the flotation value of 6 inch PVC pipe - you could cut 3 foot pieces, load them under the main berth, and then glue them shut with PVC cement to make that area positive buoyancy.

I SWAG flotation value of PVC in 6 inch as roughly

2 meters (6 feet) of pipe

Volume is PI (1.5dl)^2/4 * 20 dl = 60 dl^3 or 60 Liters

Thus Volume displaced is 60 kg of water (130 pounds roughly)

Engineering toolbox tells me 6 inch PVC weighs about 1.5kG per foot, so subtract 9 kg from the above

A 6 foot piece of sealed 6 inch PVC would give me about 50 kG (110 Pounds) of flotation.

Someone check me on this since Im on a bouncy flight and am metricating while I write this.

Trouts Dream · Post by **Trouts Dream** » Wed Apr 02, 2008 11:42 am

Catigale wrote: Someone check me on this since Im on a bouncy flight and am metricating while I write this.

Are you allowed to do that publically in the US

Trouts Dream · Post by **Trouts Dream** » Wed Apr 02, 2008 12:27 pm

All in metric (convert at the end)
diameter 6 inch = 15.2 cm
length 6 ft = 182.9 cm
Volume = pi*(r^2)*length = 3.1416*(7.6^2)*182.9 = 33,189 cm^3
Water density = 1 g/cm^3 (ignore temp and salt water)
Weight of volume displaced = 33,189 g = 33.2 kg
6" PVC pipe = 3.53 lbs/ft = 9.6 kg for 6 ft
Bouyancy = 33.2-9.6 = 23.6 kg = 52 lbs per 6 ft length
It would take about 4 - 6 ft lengths to support the weight of 1 average sized man BUT if I can get 4 lenths in back end it would provide enough flotation for me to justify a 70HP engine for the back of my X.

Catigale · Post by **Catigale** » Thu Apr 03, 2008 10:21 am

Havent found my error yet, but Trouts looks correct.

Trouts Dream · Post by **Trouts Dream** » Thu Apr 03, 2008 12:55 pm

Catigale wrote: Volume is PI (1.5dl)^2/4 * 20 dl = 60 dl^3 or 60 Liters

Looks like it was in the Volume calculation.
Formula is correct. Check the batteries in your calculator.

Catigale · Post by **Catigale** » Thu Apr 03, 2008 3:50 pm

Source of error - Global waming has melted my slide rule.

Boblee · Post by **Boblee** » Thu Apr 03, 2008 3:57 pm

If the photo and the blurb that goes with it are correct they drilled a hole in the bottom of the boat, I thought I saw somewhere a while ago that Mike limmin was there but may be wrong.
If the photo is fair dinkum the boats have an awflul lot of spare flotation to rely on, the ballast would almost certanly be full as the boat would capsize but even so there is heaps of flotation in the upper deck and above that water line.
There is no way I will remove any flotation without replacing it somewhere else but the flotation bags sound feasible.
Even if the boat is split in half you could reasonablly expect to find something to hang onto, I would think.
Even our tinny has heaps of extra flotation as I don't float real well and regard under the water as not the place I want to be.

Catigale · Post by **Catigale** » Thu Apr 03, 2008 5:22 pm

If the boat gets busted Im guessing the stern with motor heads for Davey Jones locker while the bow will stay up.

Frank C · Post by **Frank C** » Fri Apr 04, 2008 3:50 am

PVC at 6" diam is REALLY BIG PIPE. Are you sure you could fit 4 under the aft berth? I don't think even one would fit under there. Anyone really intent on replacing flotation this way, consider a Plastimo water bag, filled to limits of the space, but with air instead.

Trouts Dream · Post by **Trouts Dream** » Fri Apr 04, 2008 6:41 am

That's what I was thinking Frank and as an aside less capacity for bilge water. Water would show up on the cabin sole earlier if some of the bilge had Plastmo water bags in place.
Probably have to line the bilge first so the fiberglass doesn't rip the plastimo bag.

Terry · Post by **Terry** » Fri Apr 04, 2008 7:47 am

Boblee wrote:If the photo is fair dinkum the boats have an awflul lot of spare flotation to rely on, the ballast would almost certanly be full as the boat would capsize but even so there is heaps of flotation in the upper deck and above that water line.There is no way I will remove any flotation without replacing it somewhere else but the flotation bags sound feasible.

Yes, I noticed a good portion of the cabin top remains above the waterline in the demo pic.
I just took all that styrofoam out yet again (cabin top starboard of daggerboard trunk) to see where I would run a thru deck for my new VHF cable and where I would run the cable aft to the port side of the companionway where the radio is mounted. I see it requires a long convoluted route requiring too much length of cable. Anyway I see I forgot just how much styrofoam they pack into that little space, I filled a big plastic bag with it, enough to make me re-think leaving it out, or perhaps position it elsewhere. There seems to be a lot of goofy little pieces though and I think the styrofoam has more flotation than the PVC pipe. BTW Frank is spot on about fitting a 6" diameter pipe under the aft berth, that is not going to happen, I checked and one would be lucky to get a 4" diameter under there. Back to the drawing board. Air bags or styrofoam, the latter is more economical, perhaps I could reposition my big bag of pieces under the aft berth somewhere. Actually there are a couple other unused places I could use also, plus I could aquire more styrofoam, in larger pieces to place in other places as opposed to all the little pieces I have. I don't really have a need for the cabin top space today but in future I would like to put electronics there.

parrothead · Post by **parrothead** » Fri Apr 04, 2008 7:48 am

Probably have to line the bilge first so the fiberglass doesn't rip the plastimo bag.

I you really wanted to do this, Plastimo bags would be a good choice because they are actually a bag-within-a-bag. The outer bag of woven nylon material protects the inner PVC bladder - so no extra lining of the space should be needed.

MacGregorSailors.com

MacGregorSailors.com

Removing floatation