frame - 3

[waywardson]

hello everyone.
if all goes well,
i will have some time to work on the fish trailer during january,
i really want to have it completed soon,
because i have another project waiting in the wings,
reading all of the recent posts about trailers, i started a thinkin'
why not mount an axel to the pvc frame ?
(sorry, i forgot to say what the next project is to be)
its to be a pvc frame houseboat (shantyboat variety)
that utilizes 2 liter drink bottles (foam filled) for flotation,
i havent worked out all of the details,
(any math whizzes interested in assisting ?)
my plan has been to dry fit assemble at my house,
disassemble and transport to the river,
then reassemble and glue,
but, if it could be designed and constructed to have a removeable
or hinged metal tounge and i could bolt an axel onto it,
it would be its own trailer,
anyone have an opinion ?

thanks, george, wayward son,

[angib]

This does sound interesting - in a slightly cracked sort of way!

What type/size of PVC tube are you thinking of? I presume it will be big diameter (>12"?) to give some strength, in which case I'm not sure if the drinks bottles are needed, as the tube may provide enough bouyancy. If the tubes are small (<6"?), I can't see how they would be strong enough.

The drink bottle bouyancy goes like this:
2-part bouyancy foam is typically 2lb/ft3 (pounds per cubic foot), but let's assume 3lb/ft3 to account for any under-expansion of the foam.
1ft3 = 28.3liter
A 2 liter drink bottle has 2kg of bouyancy = 4.4lb
2 liter of 3lb/ft3 foam weighs 2x3/28.3 = 0.2lb
So each bottle provides 4.2lb of net bouyancy.
I'm ignoring the weight of the plastic bottle itself, by assuming it is neutrally bouyant in water - it will be slightly better than this, but only an ounce or two.

The PVC tube and drinks bottles aren't madness for a houseboat (this is going nowhere near any waves, right?) as all the loads, both weight and boutancy, are distibuted over the whole structure. But a trailer is the exact opposite - almost all the weight goes onto the points where the axle fixes on.

So I think the only way to carry the structure would be to build a trailer with full-length bunks - and I mean full-length, the whole length of the houseboat.

And if anyone wants some historical reference on the use of strange bouyancy aids, you might like to know that the Bluebird K3 speed record boat built by Malcolm Campbell (the father) in the late 1930s had a huge number of table tennis balls sewn into many pillowcases as its ultra-lightweight emergency bouyancy.

To avoid the expense of buying that many good balls, tests were carried out on reject balls that wouldn't bounce right and they were found to withstand a moderate water depth - handy, as the manufacturer was willing to give these away for free!

Andrew

PS I think the last part of this scores 10/10 on the old fart scale.

[waywardson]

thanks for the reply,
I told my wife last night you would know how to do the math on the bottles bouyancy, (which I didnt know how to do, thanks!)
reading your post i am now assured this project is "doable",
as far as the size of the pvc pipe, i have been thinking it would be constructed out of 2" & 1 1/2", nothing bigger than that,
I should be able to construct the main frame with the 2",
the framing would need to be "engineered",
(btw, I know i'm not smart enough to do this on paper)
last week I dry fitted a 10' long ladder from 2" and it was a pretty strong assembly, this of course was with straight rungs and my plan has been for the rungs of the assembly to be on an angle, built as a floor truss (familiar with those?) would be.
my plan has been to construct at the waters edge on a private concrete ramp and then roll the assembly into the water,
(because I have thought there would always be a certain amt of flex in it,
but if its "engineered", the flex should really be minimal)
the cabin framing which will also be constructed out of pvc should provide rigidity to the deck framing,
I guess I should stay with my original plan which was to avoid constructing a trailer, I only started thinking about bolting an axel to it after reading the posts about the frameless trailers,
If I'm reading and understanding your calculations, 9 bottles which equals approximately 1 square foot of deck space would weigh 1.80 lbs and support 37.80 lbs, since the bottles stack (2 tall) theses numbers would double giving me a total weight of 3.60 lbs per square foot and would support 75.60 lbs, If these numbers are correct, they are better than what i had anticipated, so if the framework was 12' x 24' it would contain approximately 2300 bottles per layer x 2 layers for a total of 4600 botles which would support 20 thousand pounds and weigh about 900 lbs, Is this correct ? If the numbers are correct, I can reduce the total number of bottles needed, so anyway, thanks andrew for the assistance, Its a plan in progress and if im understanding correctly I know it will work, george / waywardson