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Topic: How to stiffen PVC pipe?  (Read 5683 times)

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NowhereMan

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I’ve got a jib (smaller sail in front of the main) for my AI that’s very useful in certain wind conditions. It’ll work best with a mast that is about 1” (or less) in diameter. Ideally, the mast would be 16’ (minimum is 12’), reasonably stiff, and as lightweight as possible. I currently use a 3/4” PVC pipe (class 200, the thin stuff) for the mast. It’s the perfect diameter and lightweight, and it sorta works, but is way too flexible.

Is there any way to stiffen PVC pipe without adding too much weight? Some people claim that high-density (like 8 pound) expanding foam will do the trick, but I have my doubts. A wooden dowel inside the PVC pipe seems to add a lot of stiffness and not too much weight, but I don’t think I’ll find a 12’ (let alone 16’) dowel.

Any ideas or suggestions would be appreciated!
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tedski

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What's the inside diameter of the PVC you have?  Could make a 16' dowel on the router table.
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SandyToes

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EMT conduit maybe?  It comes in 10ft lengths, but maybe one joint in there doesn't matter?  Or you could weld it.


piscellaneous

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SCH80 PVC is much thicker-walled and the gray color is UV resistant


Tyler

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+1 on the schedule 80 pvc for electrical.  Thicker wall.


yakyakyak

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Maybe 16' aluminum tube (square, round or solid round; 6061)? That's probably expensive though.
« Last Edit: June 19, 2021, 09:59:50 PM by yakyakyak »
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SlackedTide

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Ask a machinist to turn down a aluminum tube... or maybe delrin...
http://k-mac-plastics.com/acetal-delrin-af-tubes.htm

Or

CF tubing.... if you can’t find the correct length .. could always use multiple segments with a slip over style with a dowel turned down to the ID of the tubing. Just expoxy one side to keep the dowel in place. That’s how I would connect each segment, to get needed length.
« Last Edit: June 19, 2021, 11:33:40 PM by SlackedTide »
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NowhereMan

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Thanks for all of the responses.

I'd thought about CF, but that's way expensive and probably overkill, but I do like overkill...

As for aluminum, that makes a lot of sense.

As for sch 80 PVC, it's very heavy,  and still surprisingly noodle-like.

The idea of putting EMT conduit inside PVC tubing is something that I found discussed on a sailing forum. It seems that some people have used that approach to make el-cheapo masts that actually work pretty well in practice. But again, that would be heavy for my application.

I hadn't thought about delrin. I wonder how it compares to PVC in terms of weight and flex.

And wrt the PVC becoming brittle... I'd paint it, and I think it would hold up in that respect.

The internal diameter of the class 200 PVC is just a hair over 7/8" and OD is just slightly over 1".

I'm leaning towards a wooden dowel or thin aluminum tubing inside the PVC. In my non-scientific tests, it seems that 2 layers together are a huge improvement (flex-wise), as compared to either separately.

I read somewhere that lumber yards sometimes have dowels up to 16', so I'll call around. Though, I'm doubting they'd have them in 7/8"...

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Chockersetter

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1" pole pruner pole. I bought 12' at the saw shop on hwy 12 & Llano Road Santa Rosa


SlackedTide

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https://www.servocity.com/1-x-48-carbon-fiber-tubing/

Premade cf tubing really isn’t that expensive..TBH
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Fuzzy Tom

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I have an idea.  Not necessarily a good idea.  Glue or screw a bicycle tire valve into the end cap on the PVC tubing, and pump it up to about 150 PSI.

I didn't realize you had two masts on your kayak*, but if so maybe you have a ...
https://www.sailboat-cruising.com/cat-ketch-sailboats.html


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As for aluminum, that makes a lot of sense.
You can get aluminum rigid conduit. Most electrical supply houses will have it.  I believe you can get nipples of varying sizes up to 24"
« Last Edit: June 20, 2021, 11:55:45 AM by PorkchopXpress »
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SlackedTide

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This has been a fun one to figure out...
2014 Hobie Revo 13
2011 Hobie Outback - bye bye
1997 Tracker 17 Deep V<--- Money Pit


When you look outside the window, and all you see is fishing. True Story.


yakyakyak

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PVC inside PVC ......

2019 Hobie Outback
2017 Hobie Adventure Island
2016 Santa Cruz Raptor G2 - Surf/stability champ!
2015 Hobie Revolution 16 - Speedster
2016 NuCanoe Frontier 12 - Extra stable with crazy load capability

-----------------
FOR SALE
-----------------

Rods and Reels: http://www.norcalkayakanglers.com/index.php?topic=88549.0 (Shimanos, Casting/Spinning Rods + Reels


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How about a painter's pole?  This is an aluminum and fiberglass telescopic pole used by painters to reach high points and ceilings.  I have a 16' one I bought from HD for my weather station mast on my house.  Mounted to the very peak gable end of the house, it's held up to many storms.  Of course, wind load isn't anything like a sail, but still, I recall it was pretty cheap.  They are also made of hexagonal shape which is stronger and less flexy than a cylinder shape.  The extension is click-lock like a telescoping fish net. 
Under $40!
Here's a link to it;
https://www.homedepot.com/p/Wooster-8-ft-to-16-ft-Sherlock-Extension-Pole-00R0570000/100187303

And an image from HomeDepot;