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LionessRacing

Glass bottom Dinghy/Hard dodger combination?

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The pilothouse/hard dodger thread got me thinking about how to provide the function when desired and not otherwise. 

Why not create a hard dinghy out of vacuum formed Polycarbonate (lexan) or even some type of "origami" or hard chine like a "jon boat" or Dyer Dhow that has removable seats, transom and flotation (inflatable bags) 

It would be able to be stowed inverted on the cabin top of a 30+ footer and with the transom out, function as a hard dodger/ sea hood to protect the companion way and forward cockpit from rain, spray and wash while not obstructing forward visibility.

While sailing, it would allow you to stick your head out of the hatch, inspect the rig and horizon and not have to put on foul weather gear. If it's too sunny, merely snap a sunbrella panel, or mount your Solar panels inside as you prefer. 

When you arrive at your port, simply roll it upright, install the seats, transom and floation and have a glass bottom dinghy to explore in. 

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would think the material would make a poor dinghy (scratching, relatively heavy, not that stiff etc).

But you should look into thermoforming rather than stitch and glue - its one of the advantages of the material - can be thermoformed into quite complicated shapes relatively easily. 

As to 'gluing' - self-welding is often the preferred approach - you need to do decent work with a decently tight/smooth joint to weld...but it is then an easy and strong join. 

 

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I wonder if splitting this discussion into two threads is a great idea.

There is a polycarbonate kayak on a commercial tour boat near me. It has been getting hard use daily and been stored in the tropical sun for around a year or so. It is scratched up and a bit cloudy but it has held up much better than I expected.

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2 hours ago, weightless said:

I wonder if splitting this discussion into two threads is a great idea.

There is a polycarbonate kayak on a commercial tour boat near me. It has been getting hard use daily and been stored in the tropical sun for around a year or so. It is scratched up and a bit cloudy but it has held up much better than I expected.

The how to in the "Fix" forum made sense. 

there are vendors for a variety of thermo formed kayaks etc and you can get abrasion resistant polycarbonate.

Reasonable design would be to have skegs with sacrificial (SS) runners to handle the inevitable dragging. Multi-loop handholds can work for both carrying and as aids to passage around when it's inverted.

 

Thermo forming is probably a bit beyond garage fabrication, as I'd need a plan for the layouts, vs the existing panel designs. 

 

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3 hours ago, estarzinger said:

would think the material would make a poor dinghy (scratching, relatively heavy, not that stiff etc).

But you should look into thermoforming rather than stitch and glue - its one of the advantages of the material - can be thermoformed into quite complicated shapes relatively easily. 

As to 'gluing' - self-welding is often the preferred approach - you need to do decent work with a decently tight/smooth joint to weld...but it is then an easy and strong join. 

 

Solvent welding, of either but or lap joints is sensible, but preparing the but joint bevel might be a bit harder than using a void filling adhesive and reinforcing layup, including external/internal stringers to carry floors, transom thrust and abrasion resistance on hauling. 

If this made sense, having it fabricated by somebody who has the equipment to thermoform over an 8x5 ' mandrel would be sensible. 

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Beyond welding, I have seen 4 different types of adhesives used on polycarbonate

cyanoacrylate - decent for small spots but not gap filling and water exposure does apparently degrade it (!)

two-part epoxy- we all understand this and it works pretty well for the application but does usually yellow when gap filling

Two-part structural acrylics - I think usually a stronger bond than the epoxy but probably 'depends' on a lot of things.  Need static mixing nozzles to do best job

UV curable adhesives - I've never used, but am told this is the single best option - clear/non-yellowing, high bond strength.

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54 minutes ago, LionessRacing said:

there are vendors for a variety of thermo formed kayaks etc and you can get abrasion resistant polycarbonate.

Would it make sense to buy one; split off as much as is needed to fit the companionway; figure out a way to secure the split or add a new transom?

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One thing to be careful of when bonding in non-polycarbonate pieces is the high thermal expansion rate of polycarbonate - if the poly is expanding and contracting a lot, and say a ring frame of different material is not . . . it's going to create stresses.

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Back in the late 80's Jay Harman started knocking out Goggle Boats, similar to the one pictured.

( can't locate a picture of the Goggle Boat )

Made in Western Australia.

No External buoyancy bags though.

They had a lovely teak rub rail ,  hull shape was ok for round bilge rower, and were expensive for the time.

Scratched easily from dragging around on the beach.

Didn't seem to affect under water viewing much, but looked nasty out of the water.

Few sold.

 

 

 

image.png.8742c32fc6cd09d3a4b5ca2c5ad5094a.png

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scratches can be buffed out with tooth paste or or the right rubbing compound

it is common to do that on car headlite covers that yellow or fog up

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