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Model Forum / Radio Controlled / Air Models / May 2008



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transition from glass to monocoat?

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3for3 - 22 May 2008 22:08 GMT
Hello,
My three year old Seamaster ARF has the side walls separating from the
bottom hull. I want to use .75oz cloth with 30 min epoxy thinned with
alcohol to cover the bottom and bring the glass up the sides approx one inch
for strength and water proofing.

What works best when making the transition from the monocoat sides to the
glassed bottom. The monocoat under or on top of the glass? I plan on
painting the glassed area.

thanks,
rcs
The Natural Philosopher - 22 May 2008 22:45 GMT
> Hello,
> My three year old Seamaster ARF has the side walls separating from the
[quoted text clipped - 8 lines]
> thanks,
> rcs

I dii this once using nothing more than car spray on 'body putty', I did
end up painting the Monokote tho.
Tim Wescott - 23 May 2008 02:32 GMT
> Hello,
> My three year old Seamaster ARF has the side walls separating from the
[quoted text clipped - 8 lines]
> thanks,
> rcs

If you put the Monocoat under the glass you'll be able to peel the glass
off the hull as if it were Monocoat, but you won't be able to peel the
Monocoat off at all.

I'd do the glass, then Monocoat over that.

Note:

Glassing over the bottom would be the right action to take to correct
for a design defect.  It's a design change, and will have ramifications
beyond a simple repair -- not least of which it'll add weight.

Are you sure that the fault isn't just workmanship, that can be
corrected by redoing the original glue joint?

Another note:

I wouldn't thin the epoxy.  If glue is too think, use epoxy laminating
resin.

Do a web search on vacuum bagging (but don't come crying to me if you
crush your hull!).  Resins glue stuff together well, but don't add much
strength beyond that contributed by having it all glued together.  You
want the cloth saturated, but with as little resin as possible -- that's
what you get with vacuum bagging.

Signature

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Ted Campanelli - 23 May 2008 16:25 GMT
Ted shuffled out of his cave and grunted these great (and sometimes not
so great) words of knowledge:
> Hello,
> My three year old Seamaster ARF has the side walls separating from the
[quoted text clipped - 8 lines]
> thanks,
> rcs

I suggest trying to reglue the joints 1st, then if need be glass over
the area AFTER you have stripped it down to bare wood (or fiberglass).
Do the stripping by sanding - DO NOT use zip-strip or something similar
as it will leave a residue in the wood you will not be able to get out
and the residue will play havoc with the resin within a short period of
time.

Remember, the glassing IS going to add weight, plus you will need to
rebalance the plane after everything is finished.

Before thinning the resin, try heating it with a heat gun 1st.  This
will USUALLY thin it out satisfactorily.

If you insist on thinning the resin, ONLY USE acetone OR denatured
alcohol.  In any case I suggest thinning 5% BY VOLUME AND DO NOT EXCEED
10% by volume.

The thinning is going to weaken the resin, however the weakening with a
5% thinning is minimal.  Also, be aware it is going to take SEVERAL DAYS
for the resin to set up (cure), AND the resin is going to be very soft
for an additional 7 - 10 days.
Martin X. Moleski, SJ - 23 May 2008 17:01 GMT
> ... Also, be aware it is going to take SEVERAL DAYS
>for the resin to set up (cure), AND the resin is going to be very soft
>for an additional 7 - 10 days.

You can speed the cure by making a rudimentary
"autoclave"--a friend used a light bulb in an
insulated box to reduce cure times from some
fuselages he had laid up.

I don't know what temps he actually achieved
and he's moved to Florida, so I can't ask him ...

                Marty
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Six_O'Clock_High - 24 May 2008 16:26 GMT
>> ... Also, be aware it is going to take SEVERAL DAYS
>>for the resin to set up (cure), AND the resin is going to be very soft
[quoted text clipped - 9 lines]
>
> Marty

Allegedly it is warmer there. . .
 
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