Pod and boom construction

[Paul_Williams]

Any advice on constructing a tail boom for a 4m span model and to add to the fun its very slightly tapered.
I gather than a simple carbon fibre tube is likely to crack fairly easily and I haven't been too impressed with skinny rear ends on aerobatic models such as the Sunbird.

I am not familiar with the properties of carbon tube - can the problem be solved merely by using a thicker tube wall or by nesting 1, 2 or even 3 tubes together. Alternatively, will a better strength be gained by combining aluminium and carbon tubes ?
Not sure how to achieve the taper other than lightweight filler and cloth maybe.

Another option is a rolled ply tube with internal formers or even a solid foam core - but what sort of cumulative ply thickness ?

The boom including the section in the pod, is about 950mm long. 43mm diameter tapering to around 25mm (I've still got to refine the exact diameter but you get the idea.

Essentially I am looking for a sturdy result that will cope with sloping and very occasional aerotow.
Cheers
Paul

[Ian Davis]

Hello Paul

I found that a hollow flag pole similar to ones used by marching bands do the trick, at least it has on my Schweizer I5. They appear to be tapered rolled ply with a plastic outer. Maybe fishing poles are of the same construction.

Happy new year

Ian

[Ian Davis]

Hi Paul

Here's pics of the I6 (not I5)

Ian

[Paul_Williams]

Hi Ian,
that's quite an unusual idea - where did you source yours ?
Incidentally, are carbon fishing rods made in a differenbt/stronger way than normal carbon tube ?
Paul

[VinceC]

You can buy tapered fishing rod sections from an anglers shop

[Paul_Williams]

Fishing shop ?????
It was the marching band stuff that perplexed me

I've never been into this complicated method of feeding fish by dangling stuff from a rod.
As far as I've noticed in passing, the current approach is to use a lengthy carbon pole to push the worms directly into their mouths !

So I'm completely ignorant about modern rod construction, are the fibres both lengthwise and spiral ?
Would it be useful to fill the pole with expanding foam to prevent buckling ?
Paul

[terry white]

Hi Paul.
I am not sure the fishing feeder is a goer because you say you require 43mm-23mm over approx 1mtr , don't know a fishing feeder that is like that.
What worked for me some years ago was a carbon mast made for a small sailing boat or surf sailer. Purchased from a boat chandeliers.

Much stronger and stiffer then a fish feeder and can be purchased in a number of different measurements. Unfortunately quite expensive but would do your job admirably, however they can be purchased s/h on ebay. Regards Terry.

[Ian Davis]

Hi Paul

This response is getting out of control quicker than most. I have no idea what a fishing feeder is.

My original suggestion that has proved succesful as the pics show was to use a length of flagpole,( I'll leave out the marching band bit). You must have a branch of the Sally Ann or the British Legion up your way. So, the answer is simple. Go and join the organisation of your choice and make sure you are selected to carry the flag at the carnival. They won't notice if it's a bit short when you return it. Be careful to select the bottom section. This wil be somewhere near your minimum diameter and rigid over 900mm, an external covering structure to achive the max. dia. is a simple matter.

Happy new year.

Ian

[roo Hawkins]

Dragon carp in Nottingham which is a fishing shop had a box of old fishing pole sections for £5 . I think there is one in Tamworth as well. You can also make one by rolling out of card and packing tape and layering with carbon uni tape and cloth with epoxy from easy compersits . Then you can remove the card . a bit more work.

[Paul_Williams]

Ians dead right - this is getting out of hand..........
I must however remember my Father's heartfelt advice to stay away from anyone's army even if run by someone called Sally
I'm also a bit thrown as to how I can explain a sudden interest in drum majorettes to my wife

The £5 fishing poles sound good Roo, although I will of course check out Ian's suggestion as well.
My main concern is durability as I hate repairing glass/carbon.

Is there any value or virtue in stiffening/strengthening such tube with foam or a vertical and horizontal X of balsa ?
Thanks for the help guys
Paul