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DIY Mast Construction

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downunder
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Re: DIY Mast Construction

Postby downunder » Mon Nov 02, 2015 8:02 am

Oki,

another question before I jump onto my StrutOmast:

I've noticed some of you post cure epoxy on elevated temperature. So do I.

But today I've tried pouring hot, like boiling water over some epoxy samples. They all go really soft, can bend if with almost no effort.

I can't imagine pouring hot water over carbon bike which goes wobbly after that :)

How do they doing it? Stopping hot environment affecting epoxy stiffness?

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Re: DIY Mast Construction

Postby Denisesewa » Mon Nov 02, 2015 3:11 pm

downunder wrote:Oki,

another question before I jump onto my StrutOmast:

I've noticed some of you post cure epoxy on elevated temperature. So do I.

But today I've tried pouring hot, like boiling water over some epoxy samples. They all go really soft, can bend if with almost no effort.

I can't imagine pouring hot water over carbon bike which goes wobbly after that :)

How do they doing it? Stopping hot environment affecting epoxy stiffness?
I've never heard of pouring hot water on carbon except to soften it enough to straighten a twist of something,when I do post cure I use a box and a heater with a cooking thermometer, bring the part up to recommended temp very slowly and keep it there for 6 hours , this is enough for the resin I use and my purposes, some people post cure surfboards by leaving them in a hot car, most of the epoxies the home builder uses are designed to cure at room temps and fully cure in about ten days so post curing isnt really necessary. I did not post cure the DIY foil I am riding now and its going strong for almost a year now.
All the above is just my opinion from my experience , I'm sure others will share theirs

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Bille
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Re: DIY Mast Construction

Postby Bille » Mon Nov 02, 2015 5:05 pm

downunder wrote: ...

But today I've tried pouring hot, like boiling water over some epoxy samples. They all go really soft, can bend if with almost no effort.
...
What temp does your epoxy say to cure at ; on the data sheet ?
What temp is boiling water ?

BIlle

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downunder
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Re: DIY Mast Construction

Postby downunder » Tue Nov 03, 2015 3:31 am

Thanks for your reply guys

Sorry I wasn't clear: I did not post cure with hot water, got a PID and a silicone blanket for that.


What I did as a test is: I submerged some of my old epoxy samples in hot water from our office hot water dispenser and they went wobbly. How hot is water, duno. Hot.

Using West Systems 105. Tested samples with Entropy CLR as well. To be fair, none of this epoxies post cure for improved structural properties. We do that for speeding a curing process.

Any DIY home epoxy will go wobbly, the question is on which temperature or how hot is in your car over the summer? And, is post curing really preventing this?

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Re: DIY Mast Construction

Postby GBH Riv » Fri Nov 13, 2015 5:22 am

Update : this one is 500mm long and 550g next one full length and carbon.
Attachments
2015-11-13 11.24.30.jpg
2015-11-13 11.24.09.jpg

revhed
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Re: DIY Mast Construction

Postby revhed » Fri Nov 13, 2015 8:28 am

downunder wrote: Any DIY home epoxy will go wobbly, the question is on which temperature or how hot is in your car over the summer? And, is post curing really preventing this?
Respectfully, I must disagree.
I,We have DIY Epoxy carbon layups from 2010 that are as strong and stiff as they were the day we post cured them.
We have left them in VERY hot greenhouse effect cars and on the cooking beach,( Summer South France ) still no probs.
Are we missing something?
R H

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Re: DIY Mast Construction

Postby Bille » Fri Nov 13, 2015 6:43 pm

revhed wrote: ...
Respectfully, I must disagree.
I,We have DIY Epoxy carbon layups from 2010 that are as strong and stiff as they were the day we post cured them.
...
R H
revhed is correct ; not all epoxy , is made equal. The black carbon, can bring up the
temperature of a part, high enough to melt a foam core , on a hot sunny day ; it will also
soften a cheap grade epoxy.

If you use cheap epoxy ; then
you should paint the part white, to keep the temp down a bit. Any foam-core part i make
with a carbon skin ; it gets painted white . I don't use a foam core, very much.

Bille


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