RN pole fiberglass thickness.

Req

Location
SW Tenn
I have a round nose pole that is just too short. I am debating making a completely new fiberglass section out of 4 layers of 1708 wrapped around a construction foam core that has accommodations for a single 2" breather tube. I would shape it as close to the original pole except I dont plan on putting a bend in it like the stock pole has.

I am not really concerned about getting it to mate up to the aluminum ends, I would give it a bit extra material where it presses in so any grinding to make it fit should not mess with the structure. I am mostly concerned about the hand layup and whether 4 layers will be strong/light enough. From what I have seen 4 layers is pretty beefy but before I invest 15 hrs into something I wanted to make sure it was not a waste.


Thanks for the input and any suggestions!
 
I think your going to be light with that layup. I would say calculate your fabric and resin weight, and if your in the 75% range of stock with the same dimensions you would be good. I would take some time to think about stress points and add a little to the bottom third of the pole. Think about adding some horizontal reinforcement to the bolt area to avoid any potential crush action, the side loads on a pole can be really focused high loads. Starting the layup with the short pieces first (reinforcing) and ending with the longest (full coverage) area pieces. Making a pole that is light and strong is a daunting task. GL I look forward to your posts. If you want a practical example of the loads , make a cardboard pole and then bolt it in and start bending it , you will find the stress points real quick.
 
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Req

Location
SW Tenn
Thanks for the input and I agree with everything you say. I think tapering the thickness so it is thicker at the hull end specifically would help, I would make the diameter of the foam slightly smaller to accommodate the extra material in the load points.

I was planning on using balsa wood to cut the pattern and sand the foam down to the balsas edge, I could also cut some fiberglass plate if rot is a concern. Using a denser material every few inches will make shaping the foam with a sander much easier I suspect.

Additionally I wonder if a varied layup schedule without matting backer would help, changing the orientation every layer. Something like 17oz biax / 10oz cloth / rotate 45 / 17oz biax / 10oz cloth / rotate 45 / 17oz biax / 10oz cloth.
 
I think you should layup some 10oz in a sheet and use that as a substitute for the balsa. Maybe even take the time to build a stress box for the bottom and top of the pole prior to laying the rest (subassembly). Definitely if you have enough material varie the orientation of the layers .
 
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