non-POL, non-flame, rocket-related post (honest!)

non-POL, non-flame, rocket-related post (honest!)

Post by Ted Phipp » Fri, 24 Jul 1998 04:00:00



I was sitting in my shop, waiting for some glue to dry, and started looking
at my THOY Phoenix kit (see below *) which got me to wondering...

The Phoenix kit has a regular rocket-cardboard body tube, and plywood CR's
and fins.

Why wouldn't I build this with plain ol' yellow carpenters glue instead of
epoxy?  The recommended motor list is G125, H55, H70, H120, and H100.  Way
bigger than I'm used to.  

It seems to me that the glue would be as strong, probably stronger, than
epoxy given the materials.  Except for some epoxy fillets for the fins for
cosmetic purposes, the weight savings by using yellow glue might bring the
finished weight closer to the 'listed' weight than what normally happens.

Instead of fibreglass, why not use heavy bond paper in the body/fin joint?
Given the premise of using yellow glue wherever possible.  The Phoenix is a
fin snap waiting to happen, so I think something is needed.

Let's hear some discussion!  :)

(* from above)
     I won my THOY Phoenix in the monthly drawing at Magnum Hobbies
website!  I was home sick one day, and Ross called, verified my address,
and said it'd be arriving soon.  He wasn't kidding, before I knew it I had
this too-cool rocket kit, and was scaring hell out of my neighbors with the
tube/nosecone combo (I fly little rockets).  LOL
    I'm waiting for winter to build it, I'll take my time and do it right.
It incorporates some new  techniques in construction; stuff I've heard of,
but never done.  Looking forward to it.  :)

    If you haven't tried Magnum, you should.  I'm a very satisfied
customer!  Link from my site (even more below), or Rocketry Online.

        Ted
--
"It is well to remember that the entire universe, with one
trifling exception, is composed of others."  John Andrew Holmes

R. Ted Phipps  NAR #72142          (remove 'nospam' to reply)

Visit my rocketry pages (plans, tips, pix, and more) at:
http://www.geocities.com/CapeCanaveral/Hangar/8890/index.html

 
 
 

non-POL, non-flame, rocket-related post (honest!)

Post by Peter Olivo » Fri, 24 Jul 1998 04:00:00




Quote:

>Why wouldn't I build this with plain ol' yellow carpenters glue instead of
>epoxy?  The recommended motor list is G125, H55, H70, H120, and H100.  Way
>bigger than I'm used to.  

>It seems to me that the glue would be as strong, probably stronger, than
>epoxy given the materials.  Except for some epoxy fillets for the fins for
>cosmetic purposes, the weight savings by using yellow glue might bring the
>finished weight closer to the 'listed' weight than what normally happens.

>Instead of fibreglass, why not use heavy bond paper in the body/fin joint?
>Given the premise of using yellow glue wherever possible.  The Phoenix is a
>fin snap waiting to happen, so I think something is needed.

You could make carpenters wood glue work for the motors you listed,
but what makes you think it would be stronger than epoxy?  If the
right epoxy is used it will wet into the cardboard and wood
sufficiently to achieve a much higher bonding strength than yellow
glue.  Is it necessary?  From the standpoint of a few flight only
profiles probably not.  From the standpoint of  more than a few
complete flight profiles, including landings, it's a better idea.

The use of appropriate amounts of epoxy in bonding and with light
weight fillers for the fillets will allow you to get reasonably close
to the listed weight.

The base problem, however, is that you're dealing with a model of a
guided missle, not a sounding rocket or purpose built model rocket.
As such, he doesn't adhere to the fundamental design principles that
have been proven over time to work best for unguided, atmosphere
stabilized rockets.  It's much more sensitive to over building than
most other rocket kits, requiring additional nose weight even if built
to listed weight.

Short version; the Phoenix is a bad model rocket idea.  If you really
want to build and fly it decide how long you want to keep it active
and build to those specs.



 
 
 

non-POL, non-flame, rocket-related post (honest!)

Post by Bob Kapl » Fri, 24 Jul 1998 04:00:00


Quote:

> I was sitting in my shop, waiting for some glue to dry, and started looking
> at my THOY Phoenix kit (see below *) which got me to wondering...

> The Phoenix kit has a regular rocket-cardboard body tube, and plywood CR's
> and fins.

> Why wouldn't I build this with plain ol' yellow carpenters glue instead of
> epoxy?  The recommended motor list is G125, H55, H70, H120, and H100.  Way
> bigger than I'm used to.  

Hey, there's nothing more political and flame baited in RMR than another
glue thread.

As far as motors for this rocket goes, don't scrimp. This is one hefty
rocket. And don't scrimp on the nose weight either, or boosts can get a bit
exciting. Given enough nose weight for stability, just about any of the AT
38mm reloads will do for this rocket. I'd consider a G125 at only 120 ns to
be a bit marginal. Did I say this rocket is heavy?

Quote:
> It seems to me that the glue would be as strong, probably stronger, than
> epoxy given the materials.  Except for some epoxy fillets for the fins for
> cosmetic purposes, the weight savings by using yellow glue might bring the
> finished weight closer to the 'listed' weight than what normally happens.

I did just this with my THOY Hornet (Graduator/Initiator sized model) and
have flown it on as much as an H238 with no problem. Yellow glue bonds are
at least as strong as the paper and wood that they bond to. Once the
adhesive exceeds the strength of the materials being bonded, more strength
doesn't make it any better.

My Phoenix is old, from before the Rocket R&D buyout of THOY. The centering
rings didn't fit perfectly,and the fins and slots needed some cleanup to fit
properly. I don't know if things are any better or worse now.

Quote:
> Instead of fibreglass, why not use heavy bond paper in the body/fin joint?
> Given the premise of using yellow glue wherever possible.  The Phoenix is a
> fin snap waiting to happen, so I think something is needed.

My fins held up thru a prang and some rough landings, but I finally snapped
one of them at ou last sod farm launch on a gentle landing. It didn't break
at the root, but just past the edge. I haven't looked at wat it's going to
take ti fix it yet.

        Bob Kaplow      NAR # 18L       TRA # "Ctrl-Alt-Del"

Kaplow Klips:   http://members.aol.com/myhprcato/KaplowKlips.html
NIRA:           http://www.nira.chicago.il.us

 
 
 

non-POL, non-flame, rocket-related post (honest!)

Post by The Silent Observe » Fri, 24 Jul 1998 04:00:00


Quote:

> I was sitting in my shop, waiting for some glue to dry, and started looking
> at my THOY Phoenix kit (see below *) which got me to wondering...

> The Phoenix kit has a regular rocket-cardboard body tube, and plywood CR's
> and fins.

> Why wouldn't I build this with plain ol' yellow carpenters glue instead of
> epoxy?  The recommended motor list is G125, H55, H70, H120, and H100.  Way
> bigger than I'm used to.

With those motors, and TMT fin mounts, there is no reason not to use
yellow glue.  As you note, it's lighter than epoxy (mainly because about
half of it evaporates during curing), and can easily form a join
stronger than the base material; there's no advantage in making a
stronger joint than that, unless you can save weight by doing so (and
you can't, not with epoxy).

For fillets, I recommend a small structural fillet of yellow glue,
allowed to cure completely (to transparency), followed by lightweight
spackle or Fill n' Finish smoothed into place with a finger.  Once the
filler is completely dry, it can be easily sanded to the exact fillet
profile you want, hardened by flowing on thin CA, and final sanded for
smoothness.

The fins on my Thug, constructed this way using 1/8" aircraft plywood in
a paper tube, mounted TMT and sandwiched between centering rings, broke
outboard of the fillets when the rocket impacted a solid object sans
recovery device -- one fin was longitudinally torn completely free, the
other bent and cracked, and there wasn't a single crack in the fillets.

You gain nothing beyond this kind of performance by adding more weight
in the form of epoxy.

Quote:
> Instead of fibreglass, why not use heavy bond paper in the body/fin joint?
> Given the premise of using yellow glue wherever possible.  The Phoenix is a
> fin snap waiting to happen, so I think something is needed.

Unnecessary -- see above -- though you might want to paper over the
surface of the fin itself, in order to add strength or stiffness.

Quote:
> Let's hear some discussion!  :)

I've said all this before, and I'll say it again.  B)

--
 WARNING!!  This area has been designated an official DOPE FREE ZONE!!

      If you're going to be a dope, please do it somewhere else!

Donald Qualls, aka The Silent Observer           NAR # 70141-SR Insured
Rocket Pages             http://members.aol.com/silntobsvr/launches.htm

Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.

 
 
 

non-POL, non-flame, rocket-related post (honest!)

Post by spamfre » Sat, 25 Jul 1998 04:00:00



Quote:

>I did just this with my THOY Hornet (Graduator/Initiator sized model) and
>have flown it on as much as an H238 with no problem. Yellow glue bonds are
>at least as strong as the paper and wood that they bond to. Once the
>adhesive exceeds the strength of the materials being bonded, more strength
>doesn't make it any better.

Actually... I've found experimentally that while yellow glue is
usually a great replacement for epoxy, it cracks rather easily when
completely dry and it is flexed - easier than epoxy does. So for
surface mounted fins on LMRs, I prefer epoxy, which has less tendency
to crack. For TTW fins, yellow glue seems to do fine, it just doesn't
like to be "flexed". Surface mount fin glue joints tend to flex when
the rocket hits the ground hard, etc. I always use yellow glue for
centering rings and stuff, as I find it much easier to work with and
clean up after than epoxy.

I read your recent sidebar on balsa, ply, etc. in sprocketry... I
think you're being a bit conservative. I make centering rings on LMR's
in the 2-3lb range with two 3/16ths balsa sheets laminated with grain
at 90 degrees apart, glued together with yellow glue, and anchor shock
cord mounts with eyebolts in the center. Also drill lots of 1/4"
diameter holes in them to pass ejection gasses.  Even after over 20
flights on 29mm G40, G80, G33, G64 engines, the first centering ring I
made of this type has not broken. It's very light. For engine tube
centering rings and such on LMR's in this range with 3" to 4" diameter
airframes (well, mailing tubes, really :), I tend to just use ordinary
corrugated cardboard.  No need to overbuild and add too much weight.

 
 
 

non-POL, non-flame, rocket-related post (honest!)

Post by Bob Kapl » Sun, 26 Jul 1998 04:00:00


Quote:

> I read your recent sidebar on balsa, ply, etc. in sprocketry... I
> think you're being a bit conservative. I make centering rings on LMR's
> in the 2-3lb range with two 3/16ths balsa sheets laminated with grain
> at 90 degrees apart, glued together with yellow glue, and anchor shock

First, I think Tom just picked that tidbit out of a relatively recent RMR
post I made. There were 2 points in the article: (1) Ply and balsa have
about the smae strength to weight ratio. The conversion seems to be about
1:4, thus your 3/8 balsa laminate is about equivalent to 3/32 plywood.
That's a shade lighter than what is found in LMR kits, but more than
adequate. (2) Lite-Ply just isn't suitable for fins. It breaks. But it would
probably be as light as your balsa-ply rings described above.

        Bob Kaplow      NAR # 18L       TRA # "Ctrl-Alt-Del"

Kaplow Klips:   http://members.aol.com/myhprcato/KaplowKlips.html
NIRA:           http://www.nira.chicago.il.us