Make My Tinny Unsinkable

[abrogard]

My aluminium dinghy - small ten foot job - possibly (I've just learned) an old De Havilland - has three enclosed seats in it. Like there's aluminium panel front and aft of them, you can't see under them.

If I filled them with styrofoam would it be enough to make it unsinkable? Or what would?

[tuffy]

My aluminium dinghy - small ten foot job - possibly (I've just learned) an old De Havilland - has three enclosed seats in it. Like there's aluminium panel front and aft of them, you can't see under them.

If I filled them with styrofoam would it be enough to make it unsinkable? Or what would?

How do you plan on doing that, mate ?

Tuffy

[Geoff]

My aluminium dinghy - small ten foot job - possibly (I've just learned) an old De Havilland - has three enclosed seats in it. Like there's aluminium panel front and aft of them, you can't see under them.

If I filled them with styrofoam would it be enough to make it unsinkable? Or what would?

Can you get your hand underneath the seats. Are they sealed or open. If sealed they may already provide boyancy.

If open then the seat would need to be removed to filled with polystyrene.

In you fill the seats with styrene it may not make the boat totally unsinkable but would go a long way to acheiving the objective.

I recall an add by Quintrex back in the late 60's for their 12 / 14 footer boats.

The boats came with the 3 seat filled with styrene as standard equipment.

It was a selling point.

The add showed the boat filled with water + 3 or 4 guys & it was still floating with the water lapping over the gunawls.

Geoff

[Guest Aussie007]

Can you get your hand underneath the seats. Are they sealed or open. If sealed they may already provide boyancy.

If open then the seat would need to be removed to filled with polystyrene.

In you fill the seats with styrene it may not make the boat totally unsinkable but would go a long way to acheiving the objective.

I recall an add by Quintrex back in the late 60's for their 12 / 14 footer boats.

The boats came with the 3 seat filled with styrene as standard equipment.

It was a selling point.

The add showed the boat filled with water + 3 or 4 guys & it was still floating with the water lapping over the gunawls.

Geoff

yup i have the 14ft quintrex built 1970 it has floatation under all 3 bench seats its a good thing knowing you wont sink while out fishing

[arpie]

Hi

I remember seeing a pic of a tinny that had a 30cm wide rim of rubber/foam put around the whole tinny (on the outside) that added extra buoyancy so that in the event of a sinking, people could stay in the boat & still make headway towards shore or safety, even tho it was full of water. The external protection also acts as a terrific buffer against other boats, moorings & jetties & of course, sharp places, like oyster leases! Wish I could remember where I saw the pic!! The tinny had 3 or 4 people in it & they still had the outboard going, when full of water!

If you are not sure if the buoyancy is still in the seats (some of the older stuff deteriorated over time & fell out) you could always use one of those 'expanding foam' aerosols to squirt all around the inside of the seats - usually there is a couple of holes where the welds meet the floor, to shove the nozzle in?

In the meantime - Here is a good thread relating to buoyancy issues - front & back as well as under seats & around the interior edge

http://www.nmsc.gov.au/media/pages_media_files/files/buoyancy_in%20trailerboatsUpdate_nov11.pdf

cheers

Roberta

[danny412]

Just paint TITANIC on the side, should all be good after that:):):)

[abrogard]

Sorry to go missing for so long - screwup with my computer.

Thanks for all the replies.

I've been thinking I could just open the aluminium panels under the seats and fill the area with polystyrene foam.

I don't know the SG of it but it sure floats high in the water, doesn't it. Wouldn't be far from weightless. The volume of a litre of water replaced by polystyrene would be near enough to 1kg weight saved, I'd say. Or if we give polystyrene an SG of 0.1 then maybe it'd be 900gm saved?

So the big seat is about 1.2m x .3 x .2 = 0.072 google tells me. That'd be .072cu mt = 72 litres = 72kg I think.

Well with the other seat and the tiny bows seat I reckon I could about double that so I'd be looking at a bouyancy of something like 140kg.

So the question becomes: how much would the boat weigh? If it is less than about 140kg I should have a chance of making it floatable by my rough reckoning and if it is up around 200kg I'd say I've got no show.

I'll take it over the weighbridge when I get the trailer fixed up and registered - meantime maybe someone's got a ballpark figure for the typical tinnie?

[The Incredible Hull]

Hey abrogard,

My boat is unsinkable I think. Not sure if this helps, but heres the specs of my tinny:

http://www.boatsplus.com.au/boats-for-sale/quintrex-boats/quintrex-420-dory-wide-body/prod_1256.html

It has foam in both the front and back seats which runs the width of the boat. It is meant to keep the boat just slightly above water. That link should have boat weight and motor weight.

good luck.