ABS vs PVC pipe

I'm building a "haka" bench for my AI. Most people on the Hobie forum use wood slats, while some have used spine boards, various aluminum ladder-like things, and several other creative options. But, I've never seen a design based on plastic piping, and for my purposes, I think this will be the best option.

As compared to PVC pipe, ABS is stronger in the sense of being more impact resistant. It also seems to me that ABS is much stiffer, which should allow for slightly smaller diameter pipe (a good thing).

So, I'm leaning towards using ABS pipe, but was just wondering if there is any advantage to PVC that I'm missing. It seems that PVC pipe is generally used for DIY projects, while ABS is rarely used...

A side question, why a haka bench?  Doesnt the trampoline do the job beautifully? 

If it is cost, there is a well reviewed alternative at http://tampacatamarans.com/kayak/

Plastic pipe of either type does not have the deflection or load bearing strength which wooden slats do when spanning the necessary distance, plus they are very slippery in comparison. Then there is UV degradation.

FYI

PVC Sinks
ABS Floats
 

You probably found it already, but if not - here's a great thread on HAKAs. https://www.hobie.com/forums/viewtopic.php?f=69&t=37645&start=1260 (this particular page also has some discussion on HAKA made of PVC). Or you can try bamboo (it's closer to the end of that thread) 

A side question, why a haka bench?  Doesnt the trampoline do the job beautifully? 
If it is cost, there is a well reviewed alternative at http://tampacatamarans.com/kayak/

I have Hobie's tramps (had them on AI and now different set on TI), and they could not properly support even my 7 yo - it's a wet ride unless water is absolutely flat. They are more than suitable for holding stuff, but not for hiking or extra passengers. But, of course,  different tramps might work better..

With HAKA (I'm using spineboards) I (240lbs) can comfortably hike and it's pretty dry ride, unless water goes over the top.

You probably found it already, but if not - here's a great thread on HAKAs. https://www.hobie.com/forums/viewtopic.php?f=69&t=37645&start=1260 (this particular page also has some discussion on HAKA made of PVC). Or you can try bamboo (it's closer to the end of that thread) 

A side question, why a haka bench?  Doesnt the trampoline do the job beautifully? 
If it is cost, there is a well reviewed alternative at http://tampacatamarans.com/kayak/

I have Hobie's tramps (had them on AI and now different set on TI), and they could not properly support even my 7 yo - it's a wet ride unless water is absolutely flat. They are more than suitable for holding stuff, but not for hiking or extra passengers. But, of course,  different tramps might work better..

With HAKA (I'm using spineboards) I (240lbs) can comfortably hike and it's pretty dry ride, unless water goes over the top.

Yes, I’ve looked thru most of that ginormous thread. I really like the one with spineboards where the amas can  fold in. But that’s a lot more than I want to spend now. I’ll probably initially just build a “rack” for carrying some extra gear and not an actual bench for sitting on. I think PVC or ABS will work well for that.

Not sure of the span, and have no experience with AI, TI, or hakas, BUT I've found that both ABS and PVC are surprisingly flexible over any significant length, (IE too flexible). And I got a big surprise when I learned how brittle PVC can be when stressed.  Just my experience,

Not sure of the span, and have no experience with AI, TI, or hakas, BUT I've found that both ABS and PVC are surprisingly flexible over any significant length, (IE too flexible). And I got a big surprise when I learned how brittle PVC can be when stressed.  Just my experience,

Speaking of the brittleness of PVC, this video is kind of cool—if not downright cold...

Interesting vid, I'm not surprised at the PVC results, but am very surprised at the ABS flex at temp without cracking. 

Don't forget to post up your build.

Interesting concept. If you do go with pVC, make sure you have a way to store it in its exact shape. PVC will sag and distort over time. Probably ABS, too.

If you’re feeling crafty, I bet you could make something really nice using 1/4” plywood with a fiberglass or epoxy “skin”. 2x2 stringers could add rigidity. Throw some Sea Deck type foam grip on there and you’re set!

I was a plumber for 12 years and worked with both.  Both will degrade significantly with UV exposure.  They will actually turn black and look burnt if left out in the sun.  ABS would drive my nuts in the summer when installing underground sewer lines.  I would set the grade going downhill at 1/4" per foot as code says.  Then the sun would heat the top of the pipe, being black the ABS would absorb the heat quickly, the top of the pipe would grow and cause the pipe to bow towards the sun.  I had to fill the pipe with water asap to keep it from doing that.

If you go the ABS route keep in mind it could get rather warm from solar heat absorption, and both will degrade in the sun.

   Spray paint will block out the UV...       I would think you could also wrap the stress points with some carbon fiber cloth,, or just plain fiberglass cloth and  epoxy resin 

If you are just using it for storage, I'd go abs.
When I had my AI I experiment ted with all kinds of crap, but ended with spine boards.
Abs and a few flat areas with starboard would be sweet for storage though

   Spray paint will block out the UV...       I would think you could also wrap the stress points with some carbon fiber cloth,, or just plain fiberglass cloth and  epoxy resin

The gray conduit PVC is supposed to be UV resistant, so I try to use that whenever possible. In any case, it certainly wouldn't hurt to spray paint it, and it'll look a lot nicer too.

Most of the things people use as haka benches add a lot of weight to the AI, and it seems to me that the boat is already way, way too heavy. Carbon fiber would definitely be the way to go, weight-wise. Many years ago, I had a recumbent bike that came with a very heavy fiberglass seat shell, so I experimented with a few DIY carbon fiber alternatives (vacuum bagging and all). But, that a lot more work and expense than I want to deal with right now...

 The weight would be the same for either cloth..  5.6oz carbon is the same weight as 5.6 fiberglass cloth.   A single thin layer would be plenty adequate.

  If weight is a concern,, PVC Conduit is thicker = heavier than the ABS would be.