WTC material Acrylic verses polycarb

[mikelat]

As I understand polycarb expands slightly when wet, however is stronger than Acrylic. What dose every one use? I want my WTC to be see through in case of any leaks condensation etc.

[Guest]

All plastics trend to absorb

All plastics trend to absorb a certain amount of water, nylon is one of the worst culprits.

In the case of model submarine pressure hulls I wouldn't worry about it too much.

The answer to your question is that you can use acrylic or polycarbonate for your wtc, either will work fine. OTW use acrylic, D&E use polycarbonate.

Although both clear, they're very different plastics. Acrylic is a thermoset plastic, polycarbonate is a thermoplastic.

As a result of this, polycarbonate is much resistant to shock loads (i.e. impact) and is very forgiving to cut and machine. Acrylic is somewhat more brittle, but machines very cleanly- when you know what you are doing. It's also more rigid, which means it's less likely to deform, however in practice for our boats this isn't an issue, as extruded tube tends to come in sufficient thickness to allow for pressure hull integrity to beyond 10 metres crush depth.

Acrylic polishes up better than polycarbonate, and I've found the latter tends to scuff and scratch more easily.

Finally polycarbonate tends to be about twice the price of acrylic tubing, and very much harder to source in the UK. In the U.S, it's much less expensive and readily available.

If you're not bothered about having a see-through wtc, PVC is a cheap and very agreeable alternative.

Andy

[mylo]

Andy

Excellent info, summed up

Andy

Excellent info, summed up nicely.

I can confirm with my research about water absorbtion in plastics. Like you said, they all absorb a little, but the figures we are talking about are fractions of a percent in a 24 hour period, not likely to be a factor in a normal operating session. The crush depth thing is interesting though, ....say in the event the sub descends uncontrolled......how far could she go before imploding the WTC ?, I'd like to see some stats on that, but obviously it would have a lot to do with the actual WTC design, and not simply WTC diameter and wall thickness. It would make for some interesting testing...............any volunteers ?

Mylo

[Guest]

Here is a really useful

Here is a really useful website which shows exhaustive data about any of the plastics we will use in the construction of a model submarine-

http://www.plasticsusa.com/

In Norbert Brueggens book 'Model Submarine technology', there is a whole chapter devoted to the subject of pressure hulls, and it lists various suitable materials and how well they'll work in practice.

Norbert works to a 10 metre (30 feet) crush depth, which should satisfy all but the most adventurous model subber.

I use a very technical method of assessing tubing for a wtc- I sit on it! If it takes my weight without deformation, it's good to go.

Andy

[mylo]

Andy,

I like your approach

Andy,

I like your approach

Simple is best, unless of course your name is Chris.

Mylo

[pirate]

I think at depth that

I think at depth that your seals would give way before any acrylic or polycarb would crack or crush. So spend more time on making or obtaining quality control rod seals and other seals and get whatever material is most available to you.

Happy sailing.

Pete

[mylo]

Pete,

Excellent point, I'm sure

Pete,

Excellent point, I'm sure you're right on that. .....which raises a question for me, which seals work the best and what kind of depths are we talking about that they'll hold out to ?

Rotating shaft seal and linear shaft seal.

1/4 " rod through WTC.
1/8" rod through WTC.

Anybody have any figures or first hand experience ?

Mylo

[pirate]

I've been using Skip Asays

I've been using Skip Asays inventions from SubTech for a few years. Both rotating and linear, and no problems to date. I think you can still get them from Mike Shubar.

Pete

[Guest]

You might want to think

You might want to think carefully about using subtech seals if your module is pressurised to any extent i.e. uses piston tanks.

Better to use bellows or o-ring seals instead of lip seals.

Andy

[Guest]

Acrylic vs. polycarb

I vote for polycarbonate (Lexan). I once had an acrylic WTC tube fracture when I pressed an endcap in. Polycarb resists fractures, and is easier to handle. It is more expensive, however.

[pirate]

Andy is correct about pressurized

Andy is correct about pressurized WTCs. SubTech seals only work with normal to less pressure inside the WTC. If the WTC's inside pressure is higher than the atmosphere the seals will leak.

[mylo]

Art,

I appreciate that info

Art,

I appreciate that info on the end cap causing fracture thing. ....I was wondering if Lexan was worth the price, ....it likely is.

As for the seals, I will not have any internal pressure and so will likely look into the Sub Tech ones. .....what kinds of depths are guys getting with these seals ? I would like to know what depth my WTC could survive in the event of an uncontrolled sinking.

Mylo

[Guest]

Can the sub tech seals

Can the sub tech seals be used in reverse for pressure hulls.?