Thanks everyone! The fins are TTW and I used RocketPoxy for the main
construction. It's already flown once successfully without fin fillets so this
would be more aesthetics and aerodynamics than structural, although we plan to
use bigger motors.
I love the rotisserie idea, too! :)
Amazon orders can be weird sometimes. The Rectorseal showed free same day with
Prime but when I added it to the cart the earliest was Thursday (other items in
the same cart are coming today). So, I guess I’ll have to drive to a hardware
store… the horror… ;)
From: roc-chat-bounce@xxxxxxxxxxxxx [mailto:roc-chat-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Alexander Jones
Sent: Tuesday, June 7, 2016 11:56 AM
To: roc-chat@xxxxxxxxxxxxx
Subject: [roc-chat] Re: Epoxy putty
Yeah, there is a bit of a whet out problem with it, but if you dip your finger
in a bit of isopropyl alcohol and run your finger along it, it helps lubricate
and slightly softens the putty without affecting the cure, so you can get
okay-looking fillets just doing that. You can then sand it down fairly easily.
I've also used EWF to add easily sandable material on top of this stuff,
allowing you to shape it down to a nice aesthetic fillet without expending a
ton of effort to sand the epoxy clay. I like to try new techniques with each
rocket's fillets, though, and I think my next one will be using the John Coker
method, using a pretty heavily thickened/filled long cure, like West System,
then use a plastic spoon to remove the excess and shape it. I would like to
try your method, though, too, just letting gravity do its thing. My only
concern is getting it evenly distributed between fin and airframe, especially
on 3-fin models -- I like the rotisserie idea.
On Tue, Jun 7, 2016 at 11:46 AM, Kenneth Brown
<ken@xxxxxxxxxxxxx<mailto:ken@xxxxxxxxxxxxx>> wrote:
The problem with putty is that it doesn't whet out to the body and fin since
it's so viscous. I prefer to use a 60min epoxy (longer set times generally mean
a stronger bonding epoxy) filled with microspheres to thicken it slightly and
then put the body on a rotisserie horizontally to keep the epoxy from sagging.
I get very nice fin root fillets this way. I should add that I will pin the
fins in place with a couple of spots of super glue to hold the fins in place
while the epoxy cures.
Ken
On Jun 7, 2016, at 11:38 AM, Alexander Jones wrote:
Adrian, it looks like you can get this stuff at some home depot stores,
apparently in the plumbing section. On another note, I've had okay results
with the loc-tite brand stuff that's also available off the shelf at HD (I
tend to go for the stuff that's wet applicable, which might explain my
success with it re: the brittle issue), but it really depends how much stress
you're planning to put on the joint. If it's minimum diameter or you're
otherwise expecting super-high accelerations and mach+ speeds, I'd reevaluate
it....if you're staying below mach and you're using a robust fin attachment
like TTW, you should be fine. Also, all the putties are actually A+B, just
some of them combine it into one "log" of putty, with the hardener in the
outside layer, usually the colored layer, then the epoxy is the core and is
usually white or at least lighter-colored....you use a plastic knife or
something to chop off a little section of the log and just knead it together
until it's homogeneous.
On Tue, Jun 7, 2016 at 11:02 AM, Adrian P. Bailey
<adrian@xxxxxxxxxxxxxxx<mailto:adrian@xxxxxxxxxxxxxxx>> wrote:
Thanks Alexander and Mike!
I can’t get the Amazon order to work (and have been using Prime for years) so
they may not have it in stock for same day. They do have A+B epoxy putty.
It’s for fin fillets and what I’ve read is that some putty is too brittle and
the fillets break off.
From: roc-chat-bounce@xxxxxxxxxxxxx<mailto:roc-chat-bounce@xxxxxxxxxxxxx>
[mailto:roc-chat-bounce@xxxxxxxxxxxxx<mailto:roc-chat-bounce@xxxxxxxxxxxxx>]
On Behalf Of Alexander Jones
Sent: Tuesday, June 7, 2016 9:44 AM
To: roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Re: Epoxy putty
Adrian, looks like you're in luck, there's a rocketry forum post where a guy
gives a brief review of this exact product:
http://www.rocketryforum.com/showthread.php?74822-Rectorseal-EP-400-Epoxy-Putty-Works-Great!
On Tue, Jun 7, 2016 at 9:41 AM, Adrian P. Bailey
<adrian@xxxxxxxxxxxxxxx<mailto:adrian@xxxxxxxxxxxxxxx>> wrote:
Has anyone used Rectorseal Ep-400 Epoxy Putty, or have other recommendations?
I’m looking for something that Amazon can deliver today… ;)
