Version 1.0

Heavily built 4x8’ plywood sections built of 2x6? 2x8? lumber, with cross pieces, and 55 gallon drums. Sections were bolted together.

Pluses

??

Minuses

  • Stresses were enough to bend the bolts.

  • Someone must swim under the platform to screw together the bolts.

  • Very heavy.

  • Drums must be sealed ahead of time for silicon to set.

  • It’s a big pain in the ass to screw the lids on correctly.

Version 2.0

Built of overlapping sheets of plywood with 27 gallon bins for floatation.

Pluses

  • The biggest advantage by far to this design is that is stacks into a very small space for transport and storage.

Minuses

  • It takes quite a long time and effort to assemble.

  • The deck is too flexible. Some screws pulled out when a crowd was dancing. And the center submerged when the platform was full of people.

  • Also, the bins fill with water when submerged.

  • Consensus seems to be that the design limit was reached at 20’x24’.

DIY 1.0

8’x8’ frame with plywood deck and 55 gallon drums for floatation.

Pluses

  • Simple to build and very strong.

Minuses

  • Design is limited to 8’x8’. No current design for expanding it.

  • 8’x8’ platform is a bit unwieldy to move around.

  • Drums must be sealed ahead of time for silicon to set.

  • It’s a big pain in the ass to screw the lids on correctly.

Version 3.0 (design)

Deck

Probably built in sections so that it can be easily transported.

4’x8’ are easier to move around and will fit into the existing construction space.

8’x8’ - Fewer points where we have to connect sections would be far better.

How to connect the sections?

Getting this right is probably the biggest hurdle. There will be tremendous stresses on these joints.

Floatation

Simple wooden V’s or canoes to create pontoons.

Even the simplest ones will take time and effort to build, plus probably require maintenance every couple of years.

Only real advantage may be that with the right design they could be stackable.

PVC pontoons

Very simple to construct. Probably shouldn’t require any maintenance. Unknown how durable 12”+ pipe is.

EPS Foam

One of the cheaper options and easiest to put together. This is why most docks seem to use it. Should be easy to work with. We can order any size and easily cut it to size/shape.

55 gallon drums

Free. But they’ve been known to leak if not sealed right, and they’re big, heavy, and rather hard to move around.

Notes on pontoon alternatives

(followup to discussion Sunday 19 Aug 2012 @ oakland boat hackers): it looks like a glassed foam shell is going to be noticeably cheaper than solid foam for floats; I did some checking on prices and calculation of material requirements. Details below. -dave w

Tradeoffs in material cost for pontoon float construction

Assume 2 ft. diameter cylindrical pontoon float x 8 ft. lengths (probably representative of material requirements for tapered ends.)

Solid foam: volume of cylinder - pi * R\^2 * L

R = 1 ft. L = 8 ft. Volume = 8 * pi = about 25 ft\^3

Glassed foam shell: area of cylindrical surface

pi * D * L = 16 * pi = about 50 sq. ft.

Assume 1 layer of 9 oz./sq.yd. (1 oz./sq.ft.) fiberglass fabric +

1 oz./sq. ft. mixed epoxy required. Foam shell thickness 1 in.

So 50 sq. ft. shell surface will need 50/12 = 4.167 cu. ft. of foam, about 50 oz. of epoxy, and 50 sq. ft. of fabric.

Rough comparison (representative material costs - see detail below) Solid foam:

25 cu. ft. foam x $10/cu. ft. = $250

Glassed shell:

4.2 cu. ft. foam x $10/cu. ft. = $42

50 oz. epoxy x $0.80/oz. = $40

50 sq. ft. cloth x $0.80/sq. ft = $40

total $120

Material price notes: Epoxy: about $1/oz. in quart lots; down to $0.60-0.70/oz. in gallon+ quantities. (TAP Marine Grade is about $120 for 160 oz. (1 gal/resin + 1 qt. hardener); 40 oz. for \~$40.)

Glass cloth: $0.62-$0.78/sq. yd. (Aircraft Spruce/TAP princes) for style #7500 (9.6 oz/sq.yd.); range of weights and styles available

Foam: Aircraft Spruce has blue small-cell extruded foam 2 lb/cu. ft. : 4 in. thick x 2 x 4 ft. sheet (2.67 cu. ft.) for $58 ($22/cu. ft.)

Universal Foam has same size white expanded (bead) foam 2lb/cu. ft. for $25 ($9.4/cu. ft.) - probably our best bet for thick foam.

Home Depot has pink extruded foam 2 in. x 4 ft. x 8 ft. (5.33/cu. ft.) for $29 ($5.4/cu. ft.) - this stuff is the cheapest (not surprising, a lot of it gets sold for building insulation) but I don’t know if any thickness over 2 in. is available.