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PostPosted: Thu Jul 25, 2019 3:03 pm 
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Location: Columbus, Indiana
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Bill 404 21SE
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PostPosted: Tue Jul 30, 2019 4:57 am 
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Tom King wrote:
About half of them come out really easily. The others require a little heat to break down the epoxy, sort of like pulling a golf club head.


The comp-tip for My Hobie-21 se , (is NOT) made with
epoxy ; it's made with polyester, and mat-fiberglass ,
(not woven), and it has no core material for strength.

It's the reason they don't hold up well in heat ; especially
since their painted black, which absorbents heat way more
than a light color , (like white).

My comp-tip is in Good condition , (mold worthy) ; and
i am quite good at building molds . The tip is near
9-ft long ; a mold would be easy for me.
BUT
I absolutely refuse to work with polyester , and will
NOT use fiberglass mat . Epoxy and a good stitched fiberglass,
(which is 30% stronger than the same weight glass that's woven)
would make for a much stronger, more durable and lighter part
but it would cost more. Add 1/4 " thick X 3" wide Nomex honeycomb
to both sides ; and the stiffness increases by the cube of the thickness
but that isn't really needed for the extra money.

How much are you guys willing to pay, for a tip
like i just described ?

Bille


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PostPosted: Tue Jul 30, 2019 8:02 am 
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PostPosted: Tue Jul 30, 2019 9:44 am 
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Until a decent replacement can be had, for the Hobie-21
comp-tips ; i would suggest that ALL owners, who live
in a Hot climate , wet-sand their C-tip with some 220 wet/dry
paper, and paint them with a lighter color than Black.
Any light color , or white , would be good.

Polyester does Not do well in heat ; the aircraft epoxy
i use , is good for 200-F , so it will be able to take
180-F with no problem. Rutan recommends that his
home-built compost aircraft ; be painted a light color.

If you have a temp-gun ; shoot a black car in the sun , on
a 110-F + day, and see what Ya get !

Bille


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PostPosted: Tue Jul 30, 2019 11:40 am 
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Location: Lake Gaston, NC
Just a note about breaking down epoxy for removing one. I wasn't talking about the layup in the comptip. I don't know how many were installed with epoxy as an adhesive, but I have run into some. I was talking about breaking down the adhesive epoxy, and not that in the layup.

I don't know what they were stuck in with at the factory. Any factory ones I've ever removed came out pretty easily. I changed one at a Prosail event on the beach at Wrightsville. All I had to do was shake that one a little bit. The owner of that one did the install. I just did the removal for him.

Some even used Bondo, but I don't remember ever taking one out that had used Bondo. When I did the installations/upgrades, of which there were Many in the late '80's, I used West System epoxy, because I had some right in the shop with pumps, ready to go.

Epoxy used an adhesive can be broken down with heat applied to the aluminum on the outside, but of course, you have to be careful you don't put enough heat in it to damage the Comptip. It is much like pulling a golf club head, where you don't want to damage the head, but you don't need a special puller for the Comptip.

Golf Club epoxy is designed to break down at a lower temperature than that used in any composite head, so you can pull a head with less worry about damage. I would feel fine about using that for the installation of one.


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PostPosted: Wed Aug 07, 2019 6:20 am 
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Tom King wrote:
Just a note about breaking down epoxy for removing one. I wasn't talking about the layup in the comptip. I don't know how many were installed with epoxy as an adhesive, but I have run into some. I was talking about breaking down the adhesive epoxy, and not that in the layup.
...
When I did the installations/upgrades, of which there were Many in the late '80's, I used West System epoxy, because I had some right in the shop with pumps, ready to go.
...


Got it ; and i think your correct !

West systems, is a Good brand epoxy ; i'm a bit allergic to the slow
hardener, if i get in a hurry and sand it , before it's fully cured.

I want my comp-tip removable , for transport. I measured the mast
with the tip removed , and it fits on my trailer ; which is way better
than having the full length mast sticking up over my Sienna van.

I actually plan to make the splice of the comp-tip, a bit longer ; that
way it won't need glue to keep a tight interface with the aluminum
part of the mast.

Bille


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