LOC Graduator - hints and tips please

LOC Graduator - hints and tips please

Post by William R. Morga » Mon, 06 Jan 1997 04:00:00



I recently purchased a LOC Graduator as my first introduction to LMRs and
to use for Level I (or H) certification.  Obviously I will need to do some
modification to the rocket.  I am planning to certify using lower end H's
such as an H120 or H140 SUs (don't want to take the chance of loosing the
casing with this rocket).  My modification plans so far include:

1) installing a stuffer tube to about 3/4 of the way up the airframe and
leaving a parachute compartment at the top.

2) mounting the LOC shock cord mount through the upper bulkhead of stuffer
tube.

3) fibreglassing the body tube.

4) the plywood fins are through the wall, but only protrude about 1/8"
into the tube.  I was thinking about a strip of fibreglass over the fin
tab, along the inside of the tube, to "lock" the fin in place.  Will I
need to fibreglass the fins?

Anything else?  Are my plans suitable?  There has been a lot of discussion
regarding retention systems lately - any suggestions for this particular
rocket?

All suggestions are welcome.

Regards, Bill

 
 
 

LOC Graduator - hints and tips please

Post by Peter G. Olivo » Mon, 06 Jan 1997 04:00:00




Quote:

>1) installing a stuffer tube to about 3/4 of the way up the airframe and
>leaving a parachute compartment at the top.

This is good but you need to add a third centering ring.  More about this
below.

Quote:
>2) mounting the LOC shock cord mount through the upper bulkhead of stuffer
>tube.

There are as many opinions on this as there are techniques.  Use wound steel
cable or Kevlar to avoid burning since some of the material will get hit with
burning ejection material this low to the stuffer tube.

Quote:
>3) fibreglassing the body tube.

Overkill.  Not needed for H/I class rockets.

Quote:
>4) the plywood fins are through the wall, but only protrude about 1/8"
>into the tube.  I was thinking about a strip of fibreglass over the fin
>tab, along the inside of the tube, to "lock" the fin in place.  Will I
>need to fibreglass the fins?

This is where the third centering ring comes in to play.  One at the top of
the stuffer tube.  The second positioned so that it contacts the upper
portiion of the fin tabs.  This will envolve test fittings because you are
going to leave the rear centering ring off and install the motor/stuffer
tube first.  Then install the fins and fillet everywhere two surfaces make
contact, ie., outer centering ring to inside of tube, inner centering ring
to motor/stuffer tube, fins to outside of airframe, fins to motor/stuffer
tube and tibs to motor airframe on the inside.  

Be sure to test fit the rear centering ring so that it can ***up against
the rear find tabs.  You might want to install a pair of T-nuts for future
reload retention.  Then apply epoxy to the trailing surfaces and install the
rear centering ring firmly against the fin tabs and let harden up right.
Invert and fillet the inner and outer contact points of the centering ring.

This technque provides not only firmer mounting for the fins but also crush
supoport WHEN the rocket lands on a fin and prevents airframe damage.
--



 
 
 

LOC Graduator - hints and tips please

Post by Edward J. Krohn » Mon, 06 Jan 1997 04:00:00



Quote:
> to use for Level I (or H) certification.  Obviously I will need to do some
> modification to the rocket.  I am planning to certify using lower end H's
> such as an H120 or H140 SUs (don't want to take the chance of loosing the
> casing with this rocket).  My modification plans so far include:

> 1) installing a stuffer tube to about 3/4 of the way up the airframe and
> leaving a parachute compartment at the top.

Not sure why, but OK.

Quote:

> 2) mounting the LOC shock cord mount through the upper bulkhead of stuffer
> tube.

Might try 3/16" marine bungee instead of standard LOC strap, 3X rocket length.

Quote:

> 3) fibreglassing the body tube.

At least 3 wraps of 4oz glass or equiv.

Quote:

> 4) the plywood fins are through the wall, but only protrude about 1/8"
> into the tube.  I was thinking about a strip of fibreglass over the fin
> tab, along the inside of the tube, to "lock" the fin in place.  Will I
> need to fibreglass the fins?

Don't worry about the tabs.  After glueing the fins, do a small fillet
and after it has cured, rough up fillet with 150 grit.  Put a 1" wide glass
strip over the fillet.  After that has cured add a good fillet
with SIG Epoxo-lite putty.  After that has cured glass over the top of the
putty with a 2" strip of glass.  I use this technique on all my
rockets, (both level 1 & 2).  I have never had a fin break off when doing
it this way!

Quote:

> Anything else?  Are my plans suitable?  There has been a lot of discussion
> regarding retention systems lately - any suggestions for this particular
> rocket?

Sounds like your thinking, and thats the biggest part!  For motor retention,
I put blind nuts in the aft centering ring and then cut out a ring from 1/16"
aluminum sheet.  #4 screws work just fine.  The ring has an ID just smaller
than the casing of the motor.  The screws go through the ring and into the
blind nuts, holding the motor in.  You will still want to wrap the motor with
tape to get a good gas seal, but not enough that it makes the motor difficult
to get out.

Quote:

> All suggestions are welcome.

> Regards, Bill

Hope this helps,
ed TRA #3367 L2
 
 
 

LOC Graduator - hints and tips please

Post by Eric32 » Tue, 07 Jan 1997 04:00:00


Wiliam R. Morgan wrote,

Quote:
> I am planning to certify using lower end H's
>such as an H120 or H140 SUs (don't want to take the chance of loosing the
>casing with this rocket).

   Aerotech has discontinued H120s and H140s. The only 29mm single use
high power motors still available from AT are the H70 (195Ns) and H125
(330Ns, actually an I). The H55 (157Ns) is a G motor and can not be used
for certification. Also there is the Vucan H100 smoky sam which can be
used for certification.
 
 
 

LOC Graduator - hints and tips please

Post by Bob Kapl » Tue, 07 Jan 1997 04:00:00



I endorse all of Pete's comments. He too certified with a Graduator and 29mm
reload, and spent a LONG time looging for it afterwards. I remember the flight
well.

But while this is perfectly doable, I don't think it is wise. I'd recommend
something bigger, like a LOC-IV, for your certification flight. Much less
stress on the whole system, and less chance of losing the model.

Then go build your kick ***altitude model.

        Bob Kaplow      NAR # 18L       TRA # "Abort, Retry, Fail?"

 
 
 

LOC Graduator - hints and tips please

Post by Alex Merica » Tue, 07 Jan 1997 04:00:00


Quote:

> >2) mounting the LOC shock cord mount through the upper bulkhead of stuffer
> >tube.

> There are as many opinions on this as there are techniques.  Use wound steel
> cable or Kevlar to avoid burning since some of the material will get hit with
> burning ejection material this low to the stuffer tube.

I used the LOC mounting instructions (epoxy to the inside wall).  I did
coat the inside of the body tube with epoxy to strengthen it.  In 12
flights
I had no problems with this mounting (ok, 11 flights. The 12th LOOKED
fine
as it headed for the rocket eating corn.

Quote:
> [snipped great discussion about 3rd centering ring]

> This technque provides not only firmer mounting for the fins but also crush
> supoport WHEN the rocket lands on a fin and prevents airframe damage.

My Graduator had a tendency to land on the same fin again and again.  On
two flights it landed on cement.  Both times the fin broke away from the
tube.  The first time the fin tip was cracked.  I just cut away the old
fillets, epoxied the fin tip, and glued the fin back in place.    

Alex Mericas             Processor Performance      

 
 
 

LOC Graduator - hints and tips please

Post by Eric32 » Tue, 07 Jan 1997 04:00:00


 I previously wrote,

Quote:
>>Wiliam R. Morgan wrote,
>> I am planning to certify using lower end H's
>>such as an H120 or H140 SUs (don't want to take the chance of loosing
the
>>casing with this rocket).
>   Aerotech has discontinued H120s and H140s. The only 29mm single use
>high power motors still available from AT are the H70 (195Ns) and H125
>(330Ns, actually an I). The H55 (157Ns) is a G motor and can not be used
>for certification. Also there is the Vucan H100 smoky sam which can be
>used for certification.

    I should add that even if you do find an H120 somewhere you still
would not be able to use it for certification. It, like the H55, is
actually a G motor according to TMT.
 
 
 

LOC Graduator - hints and tips please

Post by Ted H. Apk » Wed, 08 Jan 1997 04:00:00


I don't think you need to worry about the stuffer tube unless there
is an issue with regards to CG slipping back with the 'chute.  If
it is that close, add nose weight.  You better check this out cause
you are putting a heavier motor in there.

As for glassing, I think this is overkill.  I've flown a 2 stager
built out of LOC 2.6" tube on a I284 to a H180 with no signs of
tube stress.  That I284 flight did result in the the 2nd stage
separating at 1st stage burnout, pulling the interstage coupler
out of the booster and deploying the 'chute at Max Q.  The 'chute
stripped but the booster tumbled to the ground and required no
repair to be ready to fly again.

The fin tabs would worry me.  It is pretty easy to make another
set of fins with tabs that would go to the motor mount.  I'd do
it.  If you don't, the other suggestions of using glass around
the fillets would probably be fine.

The best advise is to not use this rocket for level 1.  I've flown
an R&D Army Hawk which is about the same size as the graduator but
3 times heavier, on H's and it goes really high!  I had lots of fun
with my Graduator on F's and the one G I flew it on.  Unfortunately,
it drifted away on that one G flight.

Ted Apke

 
 
 

LOC Graduator - hints and tips please

Post by mike geasl » Wed, 08 Jan 1997 04:00:00


Quote:

>Wiliam R. Morgan wrote,
>> I am planning to certify using lower end H's
>>such as an H120 or H140 SUs (don't want to take the chance of loosing the
>>casing with this rocket).
>   Aerotech has discontinued H120s and H140s. The only 29mm single use
>high power motors still available from AT are the H70 (195Ns) and H125
>(330Ns, actually an I). The H55 (157Ns) is a G motor and can not be used
>for certification. Also there is the Vucan H100 smoky sam which can be
>used for certification.

I just used a Vulcan H100ss to cert level 1 last month.They are VERY
NICE engines. As far as the Graduator I used to fly it in....
It was stock. It will take the h100ss. I've since built two more from
scratch. The only things changed were shock chords and I cut much
bigger tabs in the fins. LOC should do this to their kits.
 
 
 

LOC Graduator - hints and tips please

Post by Alex Merica » Thu, 09 Jan 1997 04:00:00


Quote:

> The best advise is to not use this rocket for level 1.  I've flown
> an R&D Army Hawk which is about the same size as the graduator but
> 3 times heavier, on H's and it goes really high!  I had lots of fun
> with my Graduator on F's and the one G I flew it on.  Unfortunately,
> it drifted away on that one G flight.

> Ted Apke

I agree with Ted.  I DID certify on a Graduator, but under the 'old'
rules (G flight qualifies you for H flight).  The Graduator is not a
heavy
rocket.  Althrough I did not glass it, I did use a LOT of epoxy and mine
was 20oz with a G64 reload.  The G64 is not a full G (120n vs 160n) and
it
went plenty high (and plenty far downrange on a windy day).  Using RSIM
I
estimated that a H123 would put you at 2800ft+.  As many have said, for
your
cert. flight you want to play it safe.  To me that means aim for
1000-1500ft.
Now, for your SECOND flight....

My $.02, the Graduator on a G is a great combination.  It is large
enough
to get the adrenalin going, but small enough to fly without a waver
(does
need FAA notification).  If I were you I would go ahead and build the
kit
with the modifications recommended in the various posts and fly it with
F/G
SU engines (F50/G40 work well).  If all goes well, THEN go for level 1.

--

Alex Mericas                Processor Performance      

                              (512) 838-2522

 
 
 

LOC Graduator - hints and tips please

Post by David.A.Davi » Thu, 09 Jan 1997 04:00:00


Quote:


> > The best advise is to not use this rocket for level 1.  I've flown
> > an R&D Army Hawk which is about the same size as the graduator but
> > 3 times heavier, on H's and it goes really high!  I had lots of fun
> > with my Graduator on F's and the one G I flew it on.  Unfortunately,
> > it drifted away on that one G flight.

> > Ted Apke

> I agree with Ted.  I DID certify on a Graduator, but under the 'old'
> rules (G flight qualifies you for H flight).  The Graduator is not a
> heavy
> >SNIP<rocket.  Althrough I did not glass it, I did use a LOT of epoxy

The Graduator makes a great Level 1 bird at a reasonable cost. A great
motor is the G75-M (Now on the Level 1 cert. Listing). Use a 30" X-form
parachute to reduce drift. Expect an altitude around 2500 feet. The
only mods I would make to the kit would be a longer motor tube for the
longer motor and the addition of a third centering ring located at the
forward end of the fin slot to reduce motor tube flex. No additional
fiberglass or reinforcement is necessary. A highly recommended adhesive
is Devcon 2-Ton epoxy. For a really killer flight, try an H180-M motor!
 
 
 

LOC Graduator - hints and tips please

Post by Floyd Moo » Thu, 09 Jan 1997 04:00:00



stuff deleted...

I build my Graduator with the stock fins, body tube and engine tube and
it flew just fine.  I did replace the shock cord with a braided wire to
give better retention in case of a high V deployment, and I also used liberal
amounts of epoxy on the inside fin fillets.  I flew it numerous time on
F, G40 and G80 Single-Use and then certified using a H125 Reload.  It did
flew a mile (launched at >8000 MSL in Walden CO), but it was recovered fine
with NO damage.  If I had to do it again I might have used a heavier/larger
rocket instead to make the recovery easier, but the Graduator had no problem
with the H motor,  there wasn't even any visible instability in the flight.

--
*********************************************************
 Floyd E. Moore                  *  Voice: 970-229-2711
 Hewlett-Packard Company         *  Fax:   970-229-6439  

*********************************************************

 
 
 

LOC Graduator - hints and tips please

Post by Eric32 » Sat, 11 Jan 1997 04:00:00


Alex Mericas wrote,

Quote:
>Using RSIM
>I
>estimated that a H123 would put you at 2800ft+.

    The H123 is a 38mm motor. Graduators have a 29mm mount. Try a H180,
nearly the same total impulse in a 29mm casing.