EZI-65, 5-minute epoxy

EZI-65, 5-minute epoxy

Post by Jason L. Eckhar » Thu, 28 Dec 1995 04:00:00



I just recently finished building an EZI-65 with a 5-minute epoxy. I heard
some discussions here that 5-min might be too weak for larger motors. Should
I be worried about launching this thing (plan to use G125 first)? Is it
necessary to go back and reinforce fillets, etc. with 30-minute epoxy?

Also, anybody out there with an EZI-65 have a list of motors and corresponding
projected altitudes?

thanks, jason

 
 
 

EZI-65, 5-minute epoxy

Post by Paul Campbel » Thu, 28 Dec 1995 04:00:00



Quote:
>I just recently finished building an EZI-65 with a 5-minute epoxy. I heard
>some discussions here that 5-min might be too weak for larger motors. Should
>I be worried about launching this thing (plan to use G125 first)? Is it
>necessary to go back and reinforce fillets, etc. with 30-minute epoxy?

I almost always just use 5-min epoxy for everything except for fixing
motor mounts in body tubes - so long as you use plenty that 5-min epoxy
is still going to be way stronger than the ply in the fins or the cardboard
in the body tube.

The number one problem I've seen with EZIs (and I've made this mistake!)
is to keep pushing the airframe untill you reach the point of "ooh, it
has a 54mm motor mount, what's the smallest reload I can put in that"
at which point you drop in a J275, push it past mach and the fins fall
off .... (I have heard of people who have built them with G10 fins and
flown with J275s - but stock it's not going to work), it will fly on a
J160 with a very long delay.

        Paul

 
 
 

EZI-65, 5-minute epoxy

Post by Jonathan Sivie » Thu, 28 Dec 1995 04:00:00



Quote:
>I just recently finished building an EZI-65 with a 5-minute epoxy. I heard
>some discussions here that 5-min might be too weak for larger motors. Should
>I be worried about launching this thing (plan to use G125 first)? Is it
>necessary to go back and reinforce fillets, etc. with 30-minute epoxy?

   I would definitely go back and reinforce the fillets, etc.  5 minute epoxy
is weaker than 30 minute.  It also is more likely to be weakened by the heat
from the motor, but unless you are planning on using 54 mm motors in your
EZI this may not be a particular problem, but be sure to use 30 minute epoxy
when making your adapters.

Quote:
>Also, anybody out there with an EZI-65 have a list of motors and corresponding
>projected altitudes?

   I built my EZI a bit heavy, with an extra centering ring, longer motor tube,
baffle and reinforcement on the fillets, etc., so it weighs over 4 pounds in
most configurations.  However without the payload section it weighs almost
exactly 1500 grams (3.3 lbs.) with a 120 nt-sec G motor, and thus can be
launched with just notification (no waiver needed).  Here are some motor and
altitude combinations I registered with my Adept altimeter in the payload
section.  Most of these flights also had a beeper onboard for recovery.

G64-4    : 462'
H238-S   : 819'
H220-7SS : 1687'
H180-M   : 1162'
I161-L   : 2037'

   I hope this is helpful.

Jonathan

----------------------------------------------------------------------
|  Jonathan Sivier          |  Secretary, Central Illinois Aerospace |

|  Flight Simulation Lab    |  Tripoli #1906                         |
|  Beckman Institute        |  Home Address:                         |
|  405 N. Mathews           |    5 The Summit                        |
|  Urbana, IL  61801        |    Champaign, IL 61820                 |
|  217/244-1923             |    217/359-8225                        |
----------------------------------------------------------------------

 
 
 

EZI-65, 5-minute epoxy

Post by Jim McLaughli » Thu, 28 Dec 1995 04:00:00



Quote:

> The number one problem I've seen with EZIs (and I've made this mistake!)
> is to keep pushing the airframe untill you reach the point of "ooh, it
> has a 54mm motor mount, what's the smallest reload I can put in that"
> at which point you drop in a J275, push it past mach and the fins fall
> off .... (I have heard of people who have built them with G10 fins and
> flown with J275s - but stock it's not going to work), it will fly on a
> J160 with a very long delay.

I watched my then 15 year old scare the daylights out of Ron Schultz at
LDRS XI by flying what Alex called an EZJ - 275. Ron's comment after
the very successful flight was " Kid, don't do that again." Ron and Deb then
very graciously autographed the air frame. Ron was not then aware hoe
much the mounts had been reinforced.

The bird was tracked to a little over 5,000 feet qith a +/- 0.05 error,
so it was a straight, true boost.

The rocket was assembled in a heavily modified and reinforced manner,
with 4 centering rings holding the motor tube, serious fillets on each cr
with the epoxy pumped in through  small holes drilled in each segment,
them patched with small fiberglass patches.

The fins were very tightly mounted, with major glue fillets along the
fin / motor tube joints, the inside of the fin / body tube joint, and the
outside of the fin / body tube joint, with glass cloth reinforcement on
the outside joints.

The rocket had a weighted nose cone, with about a pound and a half of
bbs epoxied into it.  

Later it was extensively used to loft 35 mm camera payloads, launching on
J 415s. Never lost a fin, but it was finally drowned in the swamp near the
Tripoli Puget Sound Launch site near Monroe, WA.

The EZI 65 is a good bird with a lot of useages. That 4 inch body tube is
a size that lends itself well to being used for serious active payloads
like cameras and other things.

You just have to beef up the fin mounts and use it judiciously with heavy
active payloads so that the big motors don't accellerate it beyond the
ability of the fins to withstand flutter.

Jim McLaughlin                     These opinions are mine, mine, mine!
                                   And not anybody else's. So there.


 
 
 

EZI-65, 5-minute epoxy

Post by Award » Fri, 29 Dec 1995 04:00:00


Has anyone ever tried substituting G10 fins on this kit? The failures that
I have seen on the EZI-65 and kits simular to it, are not cause by the
strength of the epoxy fillets, but by the leading edge of the fins
splitting right down the middle of the fin. Sometimes it seems that the
strength from the fillets is more criticle upon landing.   Am I off base?
 
 
 

EZI-65, 5-minute epoxy

Post by Justin Gleite » Fri, 29 Dec 1995 04:00:00



Quote:

> > The number one problem I've seen with EZIs (and I've made this mistake!)
> > is to keep pushing the airframe untill you reach the point of "ooh, it
> > has a 54mm motor mount, what's the smallest reload I can put in that"
> > at which point you drop in a J275, push it past mach and the fins fall
> > off .... (I have heard of people who have built them with G10 fins and
> > flown with J275s - but stock it's not going to work), it will fly on a
> > J160 with a very long delay.

A guy from my club built a EZI with white glue!  And it held up under the power
of an I132 just fine.

Justin

 
 
 

EZI-65, 5-minute epoxy

Post by C725 » Sat, 30 Dec 1995 04:00:00


Let me jump in here, I have a scratch built 3" rocket weighing about 1.5
lbs built entirely with 5 minute epoxy that has never flown on anything
but I357 motors, this same bird has also lost the chute on one flight and
free fell from about 3'000 feet - guess what? through it all, no sign of
weakened or cracked fillets or glue (fin tabs do extend to motor housing).
On the same note, I have a 6 lb. bird with large 'wings' that has flown on
a j135 with no sign of weakening or damage - the m***is, good filleting
and construction techniques can cover a variety of evils.
 
 
 

EZI-65, 5-minute epoxy

Post by kaplo.. » Sat, 30 Dec 1995 04:00:00



Quote:
> A guy from my club built a EZI with white glue!  And it held up under the
> power of an I132 just fine.

White glue is stronger than most HPR fliers give it credit for. I would at
least upgrade to the yellow stuff. White glue suffers from the same heat
softening that most epoxies do, so I wouldn't use it for a motor mount. This
is ESPECIALLY true for the INSIDE of the motor mount where the motor goes.
I've seen white/yellow glue soften from the casing heat, and permanently
bond the casing into the motor mount by the time the model is recovered.

I'ts probably better than 5 minute epoxy for most of the wood/paper joints
in an HPR. including gluing the centering rings into the body tube, building
bulkheads and payload sections, fin/body joints and fillets, etc. Yellow
glue will actually penetrate INTO the paper and wood fibers, 5-minute never
has a chance to do so.


USPO:   HealthCare COMPARE Corp, 5ISD, 3200 Highland Av. Downers Grove, IL 60515
TPC:    (708) 241-7919 x5327            ICBM:   4149'48" North 880'51" West

"If you would like to smoke, please feel free to step outside."
                                PSA flight attendant on route to LA

Disclaimer: If this message is caught or killed, the secretary will disavow
any knowledge of my actions. These bits will self destruct in 5 seconds....

 
 
 

EZI-65, 5-minute epoxy

Post by kingr » Sun, 31 Dec 1995 04:00:00


: Has anyone ever tried substituting G10 fins on this kit? The failures that
: I have seen on the EZI-65 and kits similar to it are not caused by the
: strength of the epoxy fillets, but by the leading edge of the fins
: splitting right down the middle of the fin. Sometimes it seems that the
: strength from the fillets is more critical upon landing.   Am I off base?

Now that you mention it I think I will build one with G10 fins. I have a
few lengths of various size body tubes around the house and I need to
build a good camera carrier. As far as being off base goes, no I don't
think you are. I've seen a lot of rockets with thin fillets fly just fine
but break upon landing. I've also seen plenty of them lose fins in
flight. It's that damnable weight/performance trade off thingie at work
again!!

Eric Specht at the Dayton Network Access Company
Tripoli #1755

 
 
 

EZI-65, 5-minute epoxy

Post by Tom Zuchowsk » Sun, 31 Dec 1995 04:00:00


It takes more than solid fillets and construction techniqies to
save a rocket from high-velocity fin flutter.  I've seen such
rockets come back with half to 2/3 of the plywood fins shredded
and GONE, even though the fillets were still solid and good.  The
trick is to choose your fins' vibration frequencies carefully. <g>

TomZ

 
 
 

EZI-65, 5-minute epoxy

Post by Jerry Irvi » Mon, 01 Jan 1996 04:00:00


Quote:



> > A guy from my club built a EZI with white glue!  And it held up under the
> > power of an I132 just fine.

> White glue is stronger than most HPR fliers give it credit for. I would at
> least upgrade to the yellow stuff. White glue suffers from the same heat
> softening that most epoxies do, so I wouldn't use it for a motor mount. This
> is ESPECIALLY true for the INSIDE of the motor mount where the motor goes.
> I've seen white/yellow glue soften from the casing heat, and permanently
> bond the casing into the motor mount by the time the model is recovered.

> I'ts probably better than 5 minute epoxy for most of the wood/paper joints
> in an HPR. including gluing the centering rings into the body tube, building
> bulkheads and payload sections, fin/body joints and fillets, etc. Yellow
> glue will actually penetrate INTO the paper and wood fibers, 5-minute never
> has a chance to do so.

Note that U.S. Rockets recommends yellow glue for all paper rocket
construction steps and insulates the glue from motor heat by design.

Fiberglass U.S. Rockets recommend 30-120 minute epoxy as there is less of
a tradeoff of ultimate strength for cure time (more complete crosslinking
you know).

If it's good enough for the army . . . . .

Quote:

> USPO:   HealthCare COMPARE Corp, 5ISD, 3200 Highland Av. Downers Grove,
IL 60515
> TPC:    (708) 241-7919 x5327            ICBM:   4149'48" North 880'51" West

> "If you would like to smoke, please feel free to step outside."
>                                 PSA flight attendant on route to LA

> Disclaimer: If this message is caught or killed, the secretary will disavow
> any knowledge of my actions. These bits will self destruct in 5 seconds....

Worlds longest .sig

Jerry

see sample below      VVVVVVVVVV

--

Box 1242, Claremont, CA 91711 USA         ^^^^^^^^
Opinion, the whole thing.

 
 
 

EZI-65, 5-minute epoxy

Post by Bo Vig » Wed, 03 Jan 1996 04:00:00



: I just recently finished building an EZI-65 with a 5-minute epoxy. I heard
: some discussions here that 5-min might be too weak for larger motors. Should
: I be worried about launching this thing (plan to use G125 first)? Is it
: necessary to go back and reinforce fillets, etc. with 30-minute epoxy?

: Also, anybody out there with an EZI-65 have a list of motors and
: correspoonding projected altitudes?

30-minute epoxy is superior to 5-minute epoxy for strength. That being said,
I knowingly built my THOY Falcon with 5-minute epoxy because of my previous
successes using it (plus, I'm impatient).

The Falcon has TTW fins to the motor tube. They are also swept about 35
degrees, a significant difference from the EZI's straight leading edge.

It's flown twice on a J275 with an ALTS2 measuring 5488 ft. AGL. It weighs
5.5 lb. on the pad (including drogue, main chute and motor).

Cd, based on field data is .465 (subject to ALTS2's +/- 5% accurracy and
variability in motor performance. RSIM computed max. airspeed is 810 ft/sec.

No hint of epoxy stress or failure.

As usual, your mileage may vary.

Bo

--

_____________________________________________________________________________
 Tripoli Rocky Mountains
 \|/      /\        
 -O- /\  /~~\  /\        Bo Viger - Tripoli #1864       voice: (970) 229-6787
 /|\/~~\/    \/~~\/\     Hewlett-Packard Company          fax: (970) 229-4947

__/______\__/___/____\_______________________________________________________
Never precede any action with a statement MORE predictive than, "Watch this".

 
 
 

EZI-65, 5-minute epoxy

Post by Robert Justi » Wed, 10 Jan 1996 04:00:00


Quote:
>>> The number one problem I've seen with EZIs (and I've made this mistake!)
>>> is to keep pushing the airframe untill you reach the point of "ooh, it
>>> has a 54mm motor mount, what's the smallest reload I can put in that"
>>> at which point you drop in a J275, push it past mach and the fins fall
>>> off .... (I have heard of people who have built them with G10 fins and
>>> flown with J275s - but stock it's not going to work), it will fly on a
>>> J160 with a very long delay.
>A guy from my club built a EZI with white glue!  And it held up under the power
>of an I132 just fine.

I built my EZI with 12-hour cure epoxy and it has been pretty rigid.  Flown it on
a J-100, I-65, and last and most spectacular was the J-180.  I thought it was
going to shred..it moved major fast.  I have heard tales of them surviving J-275s
and shreding on them.  Its obviously very close to Mach on these puppies and
Mach is not meant for a 10 degree swept fin.  If I get really rich and want to
chance losing a 54mm casing, I'll try it.  Alas, I am too poor to be careless
now :(.

Laters,
Robert