Floating a boat trailer

[troy]

Need to float a 14ft boat trailer across 6 miles of sea .
How many 44 gallon drums would i need to keep it afloat as i will be towing it with my boat.
No cat comments needed. ;D ;D
Troy

[Blackened]

G'day....
Go ask the physics classes at the local uni. Haha seriously though....... wich island have you moved to and yould you really want to dunk your trailer in salt water for that long?
Dave

[Figjamm]

Unhitch the trailer at the boat ramp with the boat still strapped firmly to it.... then drive the boat to your destination.

[Spaniard_King]

Bev,

I gotta feeling troy is taking a 14ft trailer on a voyage with his 6.25m cruisecraft. I cant see the cruisecraft making it from Troys house to the water on a 14ft trailer ;D ;D ;D

Troy, 2 to be safe incase 1 gets away from you as 1 would do the job

Cheers

Garry

[Blackened]

G'day
Just had a surge of inspiration.
Use the barge
Dave

[seatime]

2 x 44s would nearly do it, lash them on top of the mudguards and down around the axle. U may need a smaller drum on the winch post.

It might work!

Steve.

[Figjamm]

I gotta feeling troy is taking a 14ft trailer on a voyage with his 6.25m cruisecraft. I cant see the cruisecraft making it from Troys house to the water on a 14ft trailer ;D ;D ;D


Ok, point taken Garry.... I must learn more about the original poster and his/her boat before replying. ;)

[blaze]

I think 1 litre will float 1kg, so a 200l drum would float 200kg less the weight of the drum
cheers
blaze

[saurian]

Simple scale troy, 1 cubic metre of floatation per 1 metric ton of weight.
Not sure of length versus / weight / placement of floatation.
Hey how bout strap it to the bottom of the cruise craft , oh i suppose
she would not handle it.
Hey get a cat and put it up top , could on mine.

[troy]

There is no barge and the only way of taking the trailer over is by towing it.
I have a 3.95 tiny over at our beach place and i have no choice but to float the trailer over there.
Troy

[Owen]

Blaze is on the money.

Here is a calculator used for scuba tanks
http://www.subaqua.co.uk/cgi-bin/cylinder-buoyancy.cgi

I guesstimated the weight of a 200l drum at 30kg and the cylinder pressure at 1 bar and got


Using Archimedes principle, buoyancy is equal to the weight of the displaced water minus the weight of the cylinder.

The cylinder is made of 30 kg of steel, (which has a density of 7.8 kg/litre).
The steel therefore has a volume of 30 / 7.8 = 3.85 litres, so the total volume is 200 + 3.85 = 203.85 litres.
The density of salt water is 1.03 kg/litre, giving 203.85 x 1.03 = 210 kg

Air has a density of 0.0012 kg/litre.
The air in a full cylinder weighs 0.0012 x 1 bar x 200 litres = 0.2 kg.

The cylinder when empty has a buoyancy of 210 kg - 30 kg = 180 kg
The cylinder when full has a buoyancy of 210 kg - 30 kg - 0.2 kg = 179.8 kg


cheers,

Owen

[isaac]

Remove axle, springs, cut it into 3 parts with a cut of saw, weld flat bar as connecting tabs back to the inner and outer of the trailer where you cut it and then drill holes throught the tabs and trailer to slot bolts into to bolt it back together. Each part of the trailer is easliy handled then and you may fit each section in your tinny seperately. Thats what my old mans mate did with a similiar sized trailer that he takes to up the cape in his ute. If afraid of cutting up trailer, continue with the 44's. ;D Ben

[saurian]

Ok , no cat comments this time.
Pull it to bits, drawbar of frame with springs , remove axle , do not cut it up , get some people together lift it on rear deck , slew drawbar up port gunnel, pad and strap the crap out of , take your time.
What about larger boat/bigger deck ???
Mount it on zodiac, tow it over ?

Hey owen, density of alloy 5083 ?, also coke bottles how much floatation in 1.25 l , 2 lt. ta

[troy]

Simple scale troy, 1 cubic metre of floatation per 1 metric ton of weight.
Not sure of length versus / weight / placement of floatation.
Hey how bout strap it to the bottom of the cruise craft , oh i suppose
she would not handle it.
Hey get a cat and put it up top , could on mine.
Saurian offer taken with a lot of thanks and when will you be up in Nth Qld. ;D ;D ;D
We might have to put the trailer under your boat to gain more of a better ride. ;D ;D ;D
Troy

[saurian]

Troy live mackay .

[timddo]

i've seen a fella do it at in the brisbane river,

Attached 6 44 litre drums to your trail, 2 at the back, 2 at the front, then one near the tow hitch. Attached to the tow hitch some strong rope and tow about 5 meters apart. The only problem is it's a slow journey. Similiar to towing a car.

[saurian]

Troy, have we put foot in mouth or am i south/north of you.
By foot i mean the nasty un"needed" comments about my tunnel.
Ta....

[griz066]

Might be a silly question BUT if there is no barge to island and you need a trailer to put a boat on.

WHAT R U GUNNA TOW THE TRAILER WITH ON THE ISLAND????????????????????????????????????

[MattsFishing]

He's saving that question for the next post. ;D ;D ;D

[DaveSue_Fishos_Two]

Griz, I have been wondering the same thing myself! Maybe Troy has a winch type of set up on the island to pull the boat and trailer from the water.
Troy, 2 x 44 gallon drums will carry the weight of that trailer no worries. To aid an easier tow, lash the drums forward of trailer centre so they will ' kick up ' a bit at the front.

Cheers

Dave

[blaze]

put the drums under the trailer, strap iether side of the axle and one 20l right at the front under tow hitch.
cheers
blaze

[DaveSue_Fishos_Two]

Good idea Blaze.

Dave

[Fishin_Dan]

There's a lot more drums involved to float the car.... But if you leave the back wheels in the water, and put extra "flaps" on the tyres, you could drive it over ;) Just don't try and steer!!! ;D ;D ;D

[troy]

Saurian only joking mate and i am north of you.
Others have asked what will i tow it with when i get it there.
I have a tractor which was taken over there when the barge was here.
Been told i will take about one and a half hours so that's going to be a lot of fuel.
The trailer i made myself so taking it for a long swim will not worry me as there is no bearings or springs involved only bush bearings where you just have a piece of galvanized pipe bolted onto the rim and you just slip it over a narrower piece welded to the trailer and drop a pin through.
Thanks
Troy

[griz066]

I would be tempted to buy 2 ski tubes and lash trailer to them then drive like you stole it ;D You may wanna lash the drums to the top of trailer for safety ::)

[catchy_fishy]

Just in case, you should have an "anchor rope" tied to the trailor so you can recover it if you have to cut loose on the journey. It'd be terrible to get halfway and lose the trailer.

Also

Would it not be better to make a proper raft with several barrels - say 8-10 barrels, and lash the trailor to the raft, and the barrels - might make the journey a bit easier (the towing part).

Involve the local sea scouts and let them have a good go at coming up with it. Check the link out for your local scout group.

http://www.seascout.org/ships/international/Australia/index.html

Mike

[snapattack]

Helicopter. You should be able to find hire for around $400 per hour. Iwould expect you could actually do it in 1 hr, 2 at worst.

[propdinger]

why not borrow a small tinny and put some wood studs across the top put trailer on the tinny upside down tie rope from the seats to the trailer to hold in place and tow the tinny much faster and safer and alot less drag

[saurian]

Sounds like 2 to 4 drums is the concensus.
But troy how are you to tow it without turning it over etc....
Typical, crappy cane bin cut down with wheels on it..

[cajunnsw]

why not borrow a small tinny and put some wood studs across the top put trailer on the tinny upside down tie rope from the seats to the trailer to hold in place #and tow the tinny much faster and safer and alot less drag


Sounds like a plan to me ... :)

[blaze]

why not borrow a small tinny and put some wood studs across the top put trailer on the tinny upside down tie rope from the seats to the trailer to hold in place #and tow the tinny much faster and safer and alot less drag


Sounds like a plan to me ... :)

To top heavy and a small swell would likely see the dingy on top of the trailer
cheers
blaze

[saurian]

Blaze , tend to agree, but if troy gets his old but out of bed early enough
might get away with it...???

[seabug]

Hi Troy,
What about building a raft as per drawing.

Plank at back of drums is below the main frame.
plank at front of drums is above the main frame

This would give you planing hull

Rise would depend on how thick you made the rear planks
Make it wide as you like for stability.
Drums lashed to timbers.
Regards
Seabug

[seabug]

You could ,if desired ,have timbers along both sides of the drums to form a cradle,to wedge the drums more securely

Cheers
Seabug

[catchy_fishy]

have you tried to charter the old barge, is it still around ? could be cheaper than a helicpoter ?

[troy]

The old barge was sold as a package deal with the previous owners beach place and the new owner is retired and does not want to go through all the dramas of getting different licences.
I will try the drums as i have seen it done before with bigger trailers but these trailers that they are using now have at least 6 tyres on them which they use instead of rollers.
So the 9 tyres all up plus the drums would give them a advantage compared to my trailer.
Thanks
Troy

[Mr__Bean]

200kg displacement per 44 gallon drum is correct.

What is the estimated weight of the trailer?

For the point of discussion lets just say 400kg to be safe, that would mean 2 drums to equal the weight.

Sure you could make it three drums for safety margin, but that would still have the drums 2/3 below the water and the trailer in the water unless pefectly balanced on the three. Now I understand it is galvanised and the affect on the trailer isn't of concern. But jeepers dragging it through the water for 6 miles should be.

For that reason, I would place many more drums under the trailer than you need to float it so that the drums actually sit up on the water and be safer to tow, the last thing you want is for it all to pull apart halfway over.

Another thought, can you get access to a couple of tinny's?

I reckon it would be easier to use 2 tinny's that have been attached together with cross boards that make them into a catamaran. They will plane on top of the water and will tow much easier than you will drag drums along. Just a thought in case there are many with tinny's at the island.

- Darren

[Roughasguts]

Interesting subject, Think I would try 10 lenghs of 14 foot pvc sewer pipe lashed underneath the trailer with end caps.

That way you could lash it up at home with sturdy Zip ties and still tow it to the boat ramp. (maybe no sharp turns)

The flat raft shape underneath would be easier to tow less resistance and likely more stable. think it would carry 400 or so kilos.

You would find a use for the pipe after you get it over as well.

And take the twenty end caps back for a refund.

Hope you take pictures through out the voyage.

[familyman]

Troy I saw on mythbusters once about a trailer left strapped to the boat and the owner was complaining of poor performance of the boat .Got me to thinking you could suspend the trailer under the cruise craft held fore and aft with ropes and just idle over to its new home,disconnect the ropes and throw the forward rope to some one on the beach then just haul it out of the water.If you are worried about the trailer and the boat bottom touching then tie some tires onto the trailer then pull it up tight to the hull.Otherwise go with the 3 44gl drums ,one on the hitch and one each end of the axle.
Cheers and good luck
jon

[seatime]

I would consult a naval architect b4 assuming a 200lt drum displaces 200 kg. I believe the shape of, and the fact they are sealed will affect the displacement. I reckon they might displace quite a bit more than 200kg. Anyway, you'll need at least 2 to stop it rolling over IMO.

[saphire]

This thread reminds me of the Myth Busters episode where they launched a trailer and boat into the water together to see if it would work. Urban legend says that this was done by someone after purchasing a boat then they complained to the people they bought it from saying that the boat did not function well. I know its got nothing to do with what you are trying to achieve but just wanted to mention it anyway.
All the best in your endevours.
saphire.

[seatime]

Just to expand on my last post, the "generic" stability calculation of 1kg weight = 1kg buoyancy only applies in freshwater and to a box shape vessel.

#The 44gal or 220lt drums are neither box shaped or floating in freshwater!

#You will get more buoyancy in saltwater ie, 1:1.025 ratio, fresh to salt.
And I don't want to think about the calculation for a sealed drum, but someone has probably done it somewhere.

#

[seabug]

"The 44gal or 220lt drums are neither box shaped "

Does not matter what shape,200lt. of air displaces a similiar (approx.)volume of water.

Regards
Seabug

[seatime]

that was uncalled 4

[seatime]

sorry, reread the posts!

[Mr__Bean]

Seabug was talking of displacement.

If you push a 200 litre drum under water you have displaced 200 litres of water, doesn't matter what shape it is to displace the water.

Buoyancy may be a different matter but displacement will occur regardless of shape.

[Grand_Marlin]

What about floatation tyres? ::)

[seatime]

Displacement won't float ur boat, buoyancy will.

[Owen]

All ya gotta worry about Troy is that Murphy's Law probably trumps Archimedes principal ;)

cheers,
Owen

[PinHead]

propdinger's suggestion was by far the best...just strap the trailer onto a tinny..bugger trying to work out how many drums required..if a tinny cannot carry a small trailer then how could it carry a couple of large lads in it...other than that...just strap the bloody thing to the CC..not as good as a cat so no point in worrying about it

[seatime]

Seabug was talking of displacement.

If you push a 200 litre drum under water you have displaced 200 litres of water, doesn't matter what shape it is to displace the water.

Buoyancy may be a different matter but displacement will occur regardless of shape.

Displacement in water is a measurement that sometimes requires complex calculation involving the weight of the vessel, any loaded weights and buoyancy. Simply put though the weight of the vessel is measured by the weight of water that has been displaced or moved out of the area the boat is occupying. Forcing a 200lt drum underwater is not a displacement calculation. A 200lt drum floating by itself is a displacement calculation.
There is no way 200kg of weight is going to force an empty 200lt drum under water, so it can't be displacing 200kg. They might displace 200lt of air but once u start applying force to push it underwater it's no longer a simple displacement of water calculation. For example a 6m Stabicraft with sealed pontoons weighs 670kg and has 2000lts of reserve buoyancy (same as 10 x 200lt drums). The Stabicraft displaces 670kg not 2000kg.
An empty 200lt drum displaces about 20kg of water, the weight of the empty drum. If u turned the drum into a 20kg solid block then it would displace 20kg of water.
Back to the original query, the trailer may displace about 200kg in the water (it's weight). 200lt drums displace about 20kg floating (their weight) and have a reserve buoyancy of about 600kg (just a guess).
regards, Steve.

ps. seabug and mr bean if u don't agree please check with a naval architect.

[Mr__Bean]

200lt drums displace about 20kg floating (their weight) and have a reserve buoyancy of about 600kg (just a guess).
regards, Steve.

Steve, there is no guess work in it and it cannot displace more than its total volume.

What you have said about the 20kg displacement is correct for an empty drum floating on the water.

The reserve buoyancy is therefore 180kg, the remainder of the 200kg of water that the drum can displace.

There is no other magical 400kg's out there somewhere, sure a boat has additional displacement due to it's freeboard, but a drum has a fixed volume that it can displace.

Once it is under it is under.

- Darren

[seatime]

Darren, Ok u picked me up on a wild guess. I did say it was a guess, and it was drums plural, I don't know how many drums will be used.

Displacement is weight v floatation. Floatation is buoyancy. U can't have displacement without the forces of floatation/buoyancy acting upwards and weight acting downwards (Archimedes' principle). And u can't have displacement with outside forces acting on the vessel, like someone pushing it under water. In your displacement theory the laws of floatation don't exist.
If I understand ur reasoning correctly u r saying 200kg placed on or under a sealed 200lt drum will push it underwater, as 200kg is it's displacement. Not possible IMO.

"boats have additional displacement due to freeboard" freeboard has nothing to do with displacement. Didn't u say shape has nothing to do with displacement, how then does freeboard effect displacement, or the volume of the drum for that matter. regards

[bungie]

Interesting subject, Think I would try 10 lenghs of 14 foot pvc sewer pipe lashed underneath the trailer with end caps.

That way you could lash it up at home with sturdy Zip ties and still tow it to the boat ramp. (maybe no sharp turns)

The flat raft shape underneath would be easier to tow less resistance and likely more stable. think it would carry 400 or so kilos.

You would find a use for the pipe after you get it over as well.

And take the twenty end caps back for a refund. #

Hope you take pictures through out the voyage.

This is the closest. Only you use 2 - 6m x 150mm PVC pipes with end cap, but the last one metre you put a 45' bend on the pipes facing up. you end up with two ski's. Should be able to get the trailer up on a plane and be over in ten min's #;D

[seabug]

''If I understand ur reasoning correctly u r saying 200kg placed on or under a sealed 200lt drum will push it underwater, as 200kg is it's displacement. Not possible IMO. "

Mr Bean is correct, it will.

Drum under water is displacing 200lt of water =200kg approx
+ the volume of the material that the drum is made of.
The steel that the drum is made of is heavier than the water it displaces
It is this difference that would cause the drum to sink.

Regards
Seabug

[Mr__Bean]

Let' s agree to differ.

We are drifting way off topic.

- Darren

[seabug]

Good Idea. :) :)

[Angla]

If you could get it onto a plane on the way over..............Then all you need is a self draining deck.

Good luck Troy

Chris

[FNQCairns]

Sounds like a great project! 2 44s either side and 2/3 or 3/4 toward the back then a half sized one on the drawbar will float the trailer without it hardly gettin wet, stability may then be a problem (suspend under?) no idea what you will encounter along the way.
20L drums are like ******* everyone wants to got rid of them, hard to believe your 14ft trailer would weigh more than 250kg even at a stretch.

It's a hard sized trailer 44s are too big 20L are too small but safety in numbers.

Bugger me I would (attempt to) just strap it under the cruisecraft nice and solid it would do it super easy.....honest :), your craft would carry near double the trailer weight topside deck, although I have no idea where you are traveling to or what the weather would be like etc. troll some lures on the way.
Don't forget the GPS to mark that new artificial reef if things go awry :-[.

cheers fnq

[Alex9797]

Any ausfishers out there own a gin palace with a davit ? Just a thought. ;)

Alex

[saurian]

Troy , pretty calm this past weekend , did you try any of the few....
theories proposed ?????
Drums still winning .
Gelsec, 200 l is 200 kg in murphies law.
Give or take a bit , what holds it down might not come back up.
Anyway good to see it has hit a nerve .
Troy get off your but and send some photos of said trailer. might get 200 more posts....???

[Reef_Ranger]

I would take the wheels off, tip the trailer upside down, attach two 14ft longs sheets of any old roofing iron, bend up the fron as best you can. Tip the trailer back over and attach two 44s on the top of the trailer.

The plan being, get ther trailer in the water, the 44s will keep it from sinking, attach two strong ropes to the front and get it all up on the plane. You will be over there in no time. The calmer the day the easier it will be.

Sounds like fun ;D,

Sam

[bungie]

what ever you do ............ get lots of photos :)

[seatime]

Ok then, I wasn't going to reply but saurian has brought me back into it.

What I think some well meaning poster's might be failing to grasp in this exercise is, and I'm not trying to be patronising. Here me out.

When you have attached something to a sealed 200lt drum, like lashing on a trailer, you now have a trailer/drum composite unit. Displacement calculations now include everthing! Whatever is attached to the drum has become part of the drum. There can't be any further calculations of the drum in isolation. Something is applying the force to either the top of the drum, or something is pulling from under. Like a trailer. Whatever is producing this force must be included as if it was a permanent part of the drum. So the shape or dimensions of the original drum have changed dramatically, and it's weight, and it's ability to float. It's now a trailer/drum.

In a pure theoretical sense, the 200lt = 200kg is true, in a pure theoretical sense.
The only way I can see this happening, in this instance, would be to fill the drums with the water. Then they would displace 200kg, sitting on the seabed, unattached to anything else.

I don't think this is what troy was looking for :)
cheers
Steve :)

[seatime]

A bit clearer; to learn the displacement of an object floating in a fluid we need to find out how much of that fluid it has moved aside. How do we do this?

We now need to measure how much of that object is immersed in the fluid. Because this will be how much fluid it has moved aside. It will move an equal weight of fluid to the mass of the immersed part of the object.

By measuring the waterline area from pre-calculated data, and assuming 1lt = 1kg we can calculate the mass of the immersed object.

In an exercise like this if the trailer is slung under the drums the only way to know how much seawater will be displaced is to know how much space will the trailer occupy underwater. Lots of external dimensions on a trailer.
If the drums are under the trailer, the waterline area and underwater area will be needed to calculate how much seawater has been displaced then convert to kilograms. Another tough external dimensions of a ribbed cylinder calculation.

I will emphasis that a 200 litre drum is an internal measurement not an external measurement. The only time you can get a 200 litre drum to displace 200 kg would be to fill it and immerse it in water. Then it would occupy a space in the water equal to a 200 lt drum, a little more including the drum casing.
regards

[blaze]

well me being a practical sort of fellow, I would tow the trailer down, get a couple of mates to lift the bugger up . Slide a couple of drums parralel to the axle, one front and one one the rear of the axle. Then I would get a heap of rope and lass them in place. Now I would put a 20 litre plastic drum and the tow hitch. Now I would get my mates to help me push it in the water and see if she floats, at this point if in any doubt I would lass the required 20l plastic ones on the extremities of the trailer (this would also help stabalise), now I would tow the bugger to where I wanted it.
So being prctical
my brain is still clear (to think about more inportant things), I havnt had to do a heap of calculations, My mates have probable laughed their butts off, we have all had a fun time and the jobs done
NOW LETS HAVE A BEER
cheers
blaze

[catchy_fishy]

I still say get the sea scouts involved. Build the raft, lash the trailer to it with barrels just in case the raft falls to pieces and get going - test it first in an estuary if you must.

the two tinny cat idea is also a good call - so is the cutting up of the trailer and re-assembly.

Please remember th poics even if it means a thriod tinny is used.

have you thought about asking who would be prepared to use their tinny ?

[troy]

Catchyfish i could use my own tinny which is a 3.95 avalon but i tend to agree with Blaze that it might roll if the sea gets a bit rough half way across .
Troy

[catchy_fishy]

Goodluck anyway