Flotation for boat rebuild

[ALMS2018]

Im at the last 5% of my boat rebuild, and now considering flotation. Upon buying the boat, i stripped out the old poly blocks,as they were covered in rat and mice crap, waterlogged and horrible.

I was told Plastic bottles, the PPE type, like coke bottles and large juice bottles are great flotation.

Is this correct ??

if I wash and dry a lot of bottles, and use a neutral cure Uv waterproof silicon, can you see this being a problem, i can keep locked tight under cavities with a few random hits of expandafoam. not to much, as i know expanda is not closed cell, and will hold water, but just a few small bursts to lock all the bottles up tight.

what do you guys think ?

Its a 20 year old boat,on a budget refurb, so can't justify spending to much on this,as I have a fairly large area to cover, but obviosuly want it seaworthy and able to float, So,if it is not safe to use bottles,I will pay whatever i have to,to do it right, but just hoping to get away with this method, by the way, Its a gullwing boat, so it already has 2 sealed, 3 metre pods attached to each side, which are self buoyant anyhow.

[myusernam]

I think the main issue is they dont stack very well/ have a lot of wasted space whereas foam can be cut to maximise the area.

[DATCOL]

P1290004.JPGStart with 5 liter oil bottles & use smaller bottles to fill the gaps i got a heap of oil bottles from a oil recycling place at Narangba

[inveratta]

I did this on a smallish sailing boat(4.7m) when I replaced the rotten foam buoyancy with pet bottles because we wanted to keep it light ....works ok in that application,and we have turned it over a few times!

I guess you could do a quick back of the envelope calc....Im thinking 1 litre volume gives 1 kg lift...how much reserve buoyancy do you need.. What is the approx volume of foam you are replacing..etc..The 5l oil bottles look to be better for a power boat as they would be more robust and less prone to wear.I would see if you can dab silicon to keep them in place...every time I see that foam if it gets wet after a few years its not in good shape.

[ALMS2018]

yes, thanx Invertta and others for replies, Id love to get my hands on soe oil bottles but im in a rural area and wouldnt know where to. I currently have 100 2l and 1.25 pet bottles, and need another 200-300 more i reckon. Its a big boat. I was thinking of using silicon to hold in place and as said eareir,i will be using small squirts of expanda foam to lock them all tight. Boat weighs around 750kg loaded.

[rayken1938]

i would be worried about he durabillity of the plastic bottles the soft drink ones do go brittle with age.
Cheers
Ray

[Chimo]

5 lt pool acid bottles are another option.
Have you considered pouring part A and B foam in the correct volumes into upright tightly contained oil or acid bottles as well?

Under gunnel bouyancy is the optimum. Check out MAST in Tasy>

Cheers
Chimo

[Chimo]

FYI

https://www.mast.tas.gov.au/recreati...ance/buoyancy/

[catshark]

what about those pool noodles the kids use in the pools. i like the oil container idea mixed up with smaller bottles, By the sounds of it your half way there with positive floatation with the two air sealed gull wings , 3mtrs long that would have to provide some lift , same like a stabicraft pontoon setup.

[catshark]

what would you use on the sides under the gunnels, or wouldnt you need it? The foam under most bench seats in tinnies, still comes under as basic floatation. If one were to fit out heaps more floatation, would you then go ahead and change the build plate, i guess depending on whether that floatation can be taken back out.

[catshark]

good read that, im thinking how much foam i could put under the floor and BAM , too much will cause the hull to capsize, so keep the foam high up as possible and in strategic locations, know where can i get this foam and start shaping.

[Noelm]

Not too sure what you mean by too much foam will make the boat capsize? Pool noodles will fall to bits in no time, don't use them, PET bottles also are not so flash, they will go brittle and be useless after a year or two, why not just use the right foam, do it once and do it right?

[PixieAU]

Not too sure what you mean by too much foam will make the boat capsize? Pool noodles will fall to bits in no time, don't use them, PET bottles also are not so flash, they will go brittle and be useless after a year or two, why not just use the right foam, do it once and do it right?

Agree. Its not the sort of thing you want to regret your decision on.

[Red October]

As I believe you are in Yamba, like me, I would suggest you go and see the guys at Yamba Welding in the industrial area and they can order you in some closed cell foam that they use in all of their boats. It does not break down like normal foam and is used in all boats built to survey. It is not that expensive as they get it at the right price.

[gazza2006au]

Remember to screw your floor down really well 40-50 bottles is a lot of buoyancy since there is nothing holding the bottles down there is nothing stopping them from pushing the floor off the screws