Making some tall tent poles

[Moondog55]

Picture of the pole

[icefest]

Yep. That's definitely a pole. I can tell from the shape and having seen quite a few poles in my time.

(Just Joking)

How much does the entire pole weigh?

[Moondog55]

The old steel pole weighed 2300g
The new composite pole weighs 110 grams less and the extra rigidity & strength is worth it IMO.
If this works out well I will spend some extra money and make a straight CF pole next time and that should weigh just 700g, all the weight in this is the Al tubing. Next winter I want the tipi to stay standing. I used the calculator linked in the early post and the Al on it's own was borderline at that wall thickness assuming a 45 kilo load at the end of an end supported tube, not an exact calculation but the closest I found

[Moondog55]

How much does the entire pole weigh?

Whoops, I think they will wind up weighing the same, I forgot to make the allowance for the epoxy resin. So no weight saving at all, just extra strength for piece of mind

[icefest]

I look forward to next years trip report!
I wouldn't be surprised if the dynamic loads get considerably higher than 45kg.

[Moondog55]

Sure; but the only calculator I found was for a cantilever, I just used that calculator with a guess work load using half the pole height. Oh! I couldn't follow the math on the formulae I found. I hope next year will be as much fun.

[icefest]

I (think I) found a calculator that let's you do hinged-hinged Euler's load calculations this is it
You might have to open it with private browsing or clear cookies when it tells you to upgrade.

[Moondog55]

What?/ Youngs modulus for 6060 tube?

[Moondog55]

http://www.engineeringtoolbox.com/prope ... _1340.html

[Moondog55]

This carbon fiber is a dream to work with, I'll upload photos later when my nephew puts the card reader into the computer but it wets out so easily and conforms so quickly that I now see why it is the future in low mass, high strength applications. I didn't have any shrink wrap so I used plastic film wrap, one layer of 40mm sleeve only as I am leaving the aluminium tube in place but over the fiberglass it should be more than strong enough.
As said before if it works out I may have to invest in some decent kit for the epoxy work, make a mandrel and use 3 layers of CF to save some real weight.
I only used 1100mm of CF sleeve to do this so I have some left over for the next project.
Slow cure West systems so 24 hours until I can check it.

[Moondog55]

So it's a little rough and ready but when I put pressure on this short section I can actually feel how much stiffer it is.
In one way I am very pleased with the result even if it is ugly as it was partially a learning exercise and I was doing it as cheaply as possible. Disappointed tho in another way as the 40mm sleeve I used has laid up more in the horizontal direction than optimum. From my reading this increases the "Hoop strength" but that isn't what is needed in this application.
Doing this again I'd use a 40mm mandrel not the 44mm tube I used, pay the postage costs for the linear sleeve and do a proper 4 layer pole.

If there is ever any interest in a group share buy keep this post in mind

[Moondog55]

And just a couple of pictures of the ugly end result

[icefest]

I wouldn't call it ugly. I think (no matter how bad) that carbon fibre always looks better. (Colorful ti looks best though)

[Moondog55]

Is there any way to make CF less fragile, so that its failure mode is less dramatic?
I was playing with some of the scrap and while exceptionally strong it is brittle, or do you just over design to avoid failure and carry a little extra mass??

[jeremy089786]

Heya Moondog,

Just came across this one and thought I would add my 2c. First of all that pole looks pretty cool. What did you use to compress it, something like duct tape or heat shrink tape?

Most people do not wrap aluminium in carbon (for long term use), due to the varying coefficients of thermal expansion (Carbon - almost nil, Aluminium - considerable). Over time a bicycle with alu poles and carbon lugs will usually come apart at the joins, especially if it is used in a wide range of temperatures. Having said that, it makes aluminium (and some other metals) a good candidate for a mandrel as if you cool it down to very low temperatures it can be removed quite easily, leaving a carbon tube.

As for premade tubes, this company has a wide and fairly reasonably priced selection, and it specifies how they are made:
http://www.carbonfibertubeshop.com/medium%20tubing.html

Another good option would be for a couple of you got together to purchase one of these bad boys...

http://www.kickstarter.com/projects/115 ... r?ref=live

From experience it is also usually worth avoiding very cheap carbon tubes as they are often just fibreglass (the inside is painted black), with a single layer of carbon on the outside for cosmetics. Alternatively they will just be pultruded with a single woven layer stuck to the outside.

Let me know if you need any help with the build and if you need any advice about making more complex pieces (curved/ tapering hollow parts).

All the best,

Jeremy.

[Moondog55]

Thanks for the offer of help.
I'm going to trial this one over next winter before making a definite decision on making a straight CF set of poles. I used gladwrap for the compression layer
Give the conflicting priorities I think my money will be spent on the new LW sleeping system and not on tents tho

[andrewa]

What about kayak paddle shaft?.....

Or not long enough?

And I suppose I'm in the lucky position of having 2 x 4 piece CF packrafting paddles, so have been able to join sections in varying combinations to suit...

But cheap paddles are easily available, aren't they?

A

[simonm]

Yep I was thinking kayak paddle shafts too.

[andrewa]

Or one of those aluminium extendable poles for a pool leaf remover.....you could have a 12' central pole! Or cut it down to size...

[Moondog55]

Well kayak shafts are very expensive and quite small in diameter and those extendable pool poles are not really that strong either.
Resistance to bending seems to be more dependent on diameter than wall thickness which is why I went with 40 and 44mm tube in the first place.
The other alternative would be a Mountain Ash sapling harvested on the way up the road, but they do get brittle as they dry out