Delrin Rod

[Jeff Hollis]

I am designing a net tent for under my tarp. I would like some 5″ struts at the corners similar to what Mountain Laurel does in theirs. The ideal it that it makes the lower side walls go up more vertical than slanted so you sleeping bag doesn’t have as much wall contact, i.e., get condensation on it. I am thinking of using 1/4 inch Delrin type rod, Acetal Homopolymer, but have never worked with it. My questions are this: Is this best material to use including diameter? If not what would be better. I plan on cutting it with a hack saw; will this work and do I need to seal the ends are anything? Grainger lists two types, 150 and AF; anyone know the difference or does it even matter?  Thanks for any replies! Jeff

[Matthew / BPL]

I used delrin pins to locate a jig on a CNC router years ago and it’s very easy to cut on a chop saw or table saw. I’m sure it would cut easily with a hacksaw as well.

You could clean up the end with a file or sandpaper.

[Jon Fong / Flat Cat Gear]

Delrin is a great machining material, just don’t expect to glue anything to it.  My 2 cents

[AG]

Carbon fiber arrow shafts? That’s what I was going to use on my similar project. They’re relatively cheap, readily available, and very light. And the net tent corner point isn’t structural in the way that, say, a peak pole is — so no worry about failure. Just another idea to ponder.

[JCH]

Do the rods need to be solid?  If not, a small(ish) diameter CF tube might be the strongest and lightest alternative.  Check out this eBay supplier…I have purchased several times…very high quality.

This 8mm x 7mm is only 19.5g per meter…your 5″ struts would be ~2.5g each.  I made some 26″ 3-section folding poles out of this tubing and they are quite sturdy.  I used bolt thread caps from Lowes (yellow) for end caps. Epoxy holds great.

[R]

+1 for CF tubes.  For a low stress application like yours, you could also get what you need from an on-line kite shop.

Delrin is floppy stuff.  Some bivy projects use it for a small hoop.  That application tensions and constrains it, effectively stiffening it.  If you’re doing straight rods, you may have to go thicker/heavier to keep them from bowing, pending your design.

[Jeff Hollis]

Thanks for all the advice everyone. What a great group on this forum.

Delrin seems to be bendable with out breaking which I thought would be a good choice, plus it’s cheap. But Carbon perks my interest but I’m not sure quite what I am looking at. JCH, on the ebay website the products are listed like this; 6*4*500 mm. The only part I’m sure of is the abbreviation for millimeter. Any help appreciated.

Also no clue how to cut it and keep it from splitting.

Ya’ll Rock, Jeff

[Matthew / BPL]

I’d worry about tubes (cf or otherwise) punching a hole through the fabric.you could round over the ends of a rod into a nice smooth end. Delrin ftw.

[R]

Those dimensions are ODxIDxL – outer diameter by inner diameter by length.

To cut them, first wrap in masking tape.  Use a fine tooth hack saw or abrasive cutting wheel (eg Dremmel).  Go slow, be gentle.  I use a hack saw and try to cut a groove all the way around before actually cutting completely through.  Be especially careful at the very end when there’s only a small amount of material attached – this is when you could accidentally peel fibers off one side or the other.

Also, be sure you get wound fiber tubing, not pultruded.  In pultruded tubes, all the fibers are parallel and the tube is much weaker than a wound tube.

One trick you can do w/ the plastic/vinyl bolt caps (aka thread protectors) is put a small washer inside them the same OD, or slightly larger, than your tube – this prevents the ends from getting crushed.  I received some from FibraPlex like this.  Also, Quest Outfitters sells carbon tent poles and end fittings in an array of sizes.

 

 

[JCH]

Jeff, I think Rene answered all your questions.  The supplier I linked sells very high quality tubing, i dont think you will have any problems with splitting if you are carefull…i just whacked them off unceremoniously with a dremmel and a cutting wheel then smoothed with sandpaper.  The bolt thread caps will prevent any chance of the ends causing fabric damage. The 0.5mm wall thickness tubing is all you need for your application.

You might find my post on MYOG shelter poles useful.

[Bob Moulder]

Good ideas already.

In a low-load application such as this, something as simple as trimmed-down bamboo chopsticks would probably work. Slather them in some polyurethane varnish or epoxy to seal.

[JCH]

Bob makes a good point…one order of Chinese take-out and you have your rod material :)  Probably not substantially heavier than the CF to boot.

[Daryl and Daryl]

Here’s another source of carbon fiber rods (both hollow and solid).

http://www.kitesandfunthings.com/

[Jeff Hollis]

Thanks again everyone. I so happen to have some bamboo skewers that will do the trick but I am afraid of durability. Good chance I’ll be attempting an AT thru hike in March which is why durability is on my mind. It seems delrin would be the best answer, just in case over 5-6 months I make a wrong step.

Cheers,
Jeff

[Matthew / BPL]

what about some 1/4 vinyl tubing from Ace Hardware? it won’t be perfectly straight because it comes off a spool but it’s reasonably stiff, very light and would just fold over if you step on it.

[Roger Caffin]

I so happen to have some bamboo skewers that will do the trick but I am afraid of durability. Good chance I’ll be attempting an AT thru hike in March
I can’t see that there would be much durability problem, but maybe you could coat the ends in something like Plasti-Dip? Or even just a bit of epoxy.

Cheers

[Bob Moulder]

 Thanks again everyone. I so happen to have some bamboo skewers that will do the trick but I am afraid of durability. Good chance I’ll be attempting an AT thru hike in March which is why durability is on my mind. It seems delrin would be the best answer, just in case over 5-6 months I make a wrong step.

One good thing about the AT is that you’ll never be very far from a Chinese restaurant. ;^)

Quite frankly there are many materials that will work. Delrin is as good a material as any and it has been around a while… there were bicycle headset bearing races being made from Delrin the 1970s.

But from a general MYOG perspective, remain “McGuyver-esque” in your approach to problem solving and you will find that in many situations viable solutions are numerous.

[Sam Farrington]

For the lightest and strongest struts, i used an Easton product called “Injexion” arrow shafts that come in a couple small diameters. The nocks made good protective tips. Have cut and ground the nocks down to a desired shape in the past, but last time left them intact so they would latch on to light webbing. Goodwinds kites have much cheaper carbon tube and solid rods, but to be able to choose from a large variety of sizes, it comes only in pultruded form, which is much weaker than the Easton shafts.  They also have a similar line in fiberglass, which is more flexible, but not in 5 inch lengths.

Unless you want to spend a lot for a Proxon saw, the little mini cross cut or chop saws are well under $50 from Harbor Freight, Amazon, etc., and the 2″ steel blades slice through carbon arrow tubing, but dull quickly on alloy tubing. A good dust mask is needed to keep the carbon fibers out of the lungs. A buffing wheel is helpful also to clean up the rough edges of the cuts.

Another way to get more floor space in the net inner might be to place vertical triangular pullouts at the corners of the bath tub floor, and run cord from the pullouts to the corner stakes supporting the tarp. You could do this, and also sew the struts into the corners of the bath tub to insure that its walls do not sag. Just makes it a little harder to fold up the inner. Something like this was done with the rear pullout in this photo, although the bathtub wall was not fully vertical and not intended to be.

[Roger Caffin]

Cutting carbon fibre tubing:
I slide the CF tubing into a bit of Al Easton arrow tubing which is a snug fit with a gap in the middle and use an ordinary hacksaw to cut through a gap in the Al tubing. Works every time, for many tent poles. But I do it GENTLY.

Cheers

 

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