Hey everybody,
I got a '79 Hobie 16 and I am trying to bring her back to life. My current project is replacing the front cross bar since the mast step is messed up and the jib controls are not what they should be. I have found a good used crossbar with everything I need. When I took the tramp off and the bolts out it looks like the frame might have been epoxied together. I don't mind messing up the old front crossbar, although I would prefer to keep it in good condition just in case. My real question is does anyone have experience taking apart an epoxied frame and do you have any technical advice for someone attempting it for the first time.
-SailorJerry2
Hobie 16 epoxied front cross bar removal
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Posted: Nov 23, 2012 - 06:30 AM
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Posted: Nov 23, 2012 - 06:51 AM
If you can't pull them apart, I have an extra 16 frame in my attic I don't need....
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Bill 404 21SE
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Posted: Nov 23, 2012 - 07:02 AM
Use a hardware store propane torch and put a little heat on the frame. That should do it.
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Mike Conway
H16
Hilton, NY
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Posted: Nov 23, 2012 - 09:04 AM
Came across this quote in an "On the Wire" article about epoxiing Hobie 16 frames. However, 140 degrees seems a little cool to me, maybe they meant 240 or 340 degrees because when my frame sits baking in the sun I know the radiant temp of that frame has to exceed 140. If that be the case and the epoxy would melt at that low a temp wouldn't epoxying a frame be a waste of time???? I plan on doing this on my '87 Hobie this spring and if anyone has thoughts on this I'd appreciate it. -
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Posted: Nov 23, 2012 - 11:27 AM
Nacraman...I sent you a PM, looking for a spec from your 5.0 if you have the time.
thanks.
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Mystere 6.0XL Sold Was a handful solo
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Posted: Nov 23, 2012 - 01:01 PM
pack some house bricks under and around to contain the heat and get that flame all around the casting for as long as it takes for lots of smoke to pour out of your furness then you will know the resin is melting -
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Posted: Nov 23, 2012 - 05:49 PM
don't think you need the epoxy to actually melt, catch fire and burn with horrible black smoke
epoxy will generally soften well before then and the bond can be broken
just build up the temperature gradually and start working the join once the casting is too hot to touch -
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Posted: Nov 28, 2012 - 05:32 PM
Thanks everyone! This is tones of help and I will keep you updated with how it goes when I try and do the work mid Dec. -
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Posted: Nov 28, 2012 - 07:57 PM
would be a good safe start
to boil up a lot of water and pour that over the 1st knuckle before you hit it with flame
move the flame around a a lot
and every 30sec or so put down the torch and give the beam a wriggle -
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Posted: Nov 30, 2012 - 10:38 AM
Hey all -- typically don't post much here, but I kind of relate to this topic right now.
I am taking an undergrad heat transfer and materials processing class currently. We just went over composites/epoxies today...
From my general understanding, it is more than likely 240 degrees F that you reach what they call the "Glass Transition Temperature, Tg." At this point, the material will break its secondary bonds and loose a lot of its strength. It will possibly get kind of tacky in this stage and allow you to pull it apart. Just make sure the heat is uniform and you do not create any "hot spots" in the process.
I have actually never been up close to a Hobie 16, so I am not entirely sure about what you are actually heating/pulling part. If this is happening on the boat, I would be very careful to not get too much heat on the fiberglass. From a heat transfer perspective, aluminium has a pretty high thermal conductivity value, k, so it is going to want to take the heat you apply and send it down its length very quickly. Although, you could probably combat this with a wet rag or ice water in the areas you do not want the heat approaching.
When it comes to putting the part back together, I would get as much of the old epoxy out as possible. I am pretty sure the mechanical properties are permanently changed after heating it so high. (although I assume it is still better than no adhesive)
Hope this helps ---- I'm not a grad student or specialize in materials, so don't take all this the wrong way haha.
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83' - Prindle 16
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Posted: Nov 30, 2012 - 02:21 PM
So, as a kid I used to help do some of this epoxying to hobie 16s, as I remember the discussion was to use a propane torch (MAP gas is hotter and available now) and a big hammer (2lbs+), lots of 2x4s (about a foot long) so that you don't damage the casting (hit the 2x4 w/ the hammer set against the casting).
Keep the heat moving around the casting and heat until you can sense the epoxy giving up, the process was to give the cross beams a light scratched/sanded surface to make the bond hold well on the crossbeam, so you'll have to get the epoxy to really breakdown/melt to pull apart.
Make sure you get the oversized(+1/32th) rivets from Murrarys or Mcmaster when you reassemble. Measure hulls when you reassemble to make sure boat is square (measure diagonals and center/center front/back). It's worth epoxying the boat when you put it back together. You might also find that a mainsheet block system will help pull apart and put back together if you have several heavy/stationary objects to tie too.
