Q: LOC graduator construction questions

Q: LOC graduator construction questions

Post by Robert Field » Fri, 09 Oct 1998 04:00:00



I just rec'd the LOC Graduator kit. This is really my second rocket. The
first being an Estes Alpha.

A few things about the kit I found less than desirable and thought that
I'd ask the experienced for your thoughts and suggestions:

1) I was suprised that the engine mount has not block, and no retaining
clip. They suggest that the engine be wrapped with masking tape to get a
nice snug fit. That is supposed to stop the engine from blowing right
through the rocket on ignition, and keep the engine in the mount when the
ejection charge blows. Seems to me that this is a really funky way to
retain an engine and that it would have been very simple and inexpensive
to develop a more explicit method of holding the engine in place. Is this
a standard way to mount engines ? Am I concerned about nothing ?

2) I was also suprised to see a slotted body tube, with cut plywood fins,
yet the fins only extend into the body tube about 1/8 inch. I would have
expeected the fins to extend all the way to the motor mount for better
structural support. Again, a very inexpensive way to provide a much more
robust rocket. Thoughts from the experts ?

Thanks in advance for your assistance !

-Robert
p.s. take a look at http://www.scibid.com/ for rocketry auctions. Complete
free and a very sophisticated auction site that caters to technical
hobbies. I've added a category for Rocketry.

 
 
 

Q: LOC graduator construction questions

Post by Gene Costanz » Fri, 09 Oct 1998 04:00:00


As far as the motor mount goes, many, if not most, med.-to-higher power
rockets have this configuration. It works. The motors fit snuggish as
they sit and 1 rev of masking tape makes them somewhat difficult to get
out. Therefore, don't put the motor to far up into the motor tube. And
bring ChannelLocks to the field.

Although it seems inadequate, the fins go plenty far enough into the
airframe to allow for structural stability and add to the amount of
surface area that gets epoxied. Don't oversand the fins if they're snug!
Let them be a little snug.

It's a nice looking and performing rocket. I flew mine WAY-underpowered
a couple times and it flew well. Far be it from me to be a DaVinci,
either, so I built mine before I was fully experienced enough.

Good luck and have fun...

P.S. I don't care WHAT the packaging says, avoid flying on a D
motor...it's just TOO heavy...E15-4 to start...

 
 
 

Q: LOC graduator construction questions

Post by Shadowra » Fri, 09 Oct 1998 04:00:00


Quote:
>1) I was suprised that the engine mount has not block, and no retaining
>clip

They dont' put an engine block in so you can use a variety of engine
cases(29mm) if you put a block in for say a D-12 you would have to remove it to
put a 29/120 RMS case in it.

I use a hose clamp to keep mine in and it hasn't failed me yet.  I don't have a
graduator so I don't know how far in the BT the back centering ring is, but I
generally leave enough room to get a hose clamp on the motor mount all you need
is 1/2 to 3/4 inch.
Shane Bryson (Shadowrat1)
"You are not intitled to an opinion. An opinion is what you have when you don't
have any facts. When you have the facts, you don't need an opinion."
                        --Solomon Short--

 
 
 

Q: LOC graduator construction questions

Post by Bob Kapl » Fri, 09 Oct 1998 04:00:00


Quote:

> 1) I was suprised that the engine mount has not block, and no retaining
> clip. They suggest that the engine be wrapped with masking tape to get a
> nice snug fit. That is supposed to stop the engine from blowing right
> through the rocket on ignition, and keep the engine in the mount when the
> ejection charge blows. Seems to me that this is a really funky way to
> retain an engine and that it would have been very simple and inexpensive
> to develop a more explicit method of holding the engine in place. Is this
> a standard way to mount engines ? Am I concerned about nothing ?

Yes, and you are. Thos rocket can be flown with motors whose length varies
from 70mm to over 200mm. And you never know when someone is going to come
out with an even longer motor. I built one for 38mm motors, and put the
motor block for the longest AT reload: an I284. Well, now there's a J350 and
a J570? that are longer still.

The tape ring works amazingly well to keep motors form going up thru the
rocket. And AT reloads have a built in ring, as do the new NCR expendables.

You do want to add positive motor retention to this rocket. See the article
refered to in my .sig for Kaplow Klips and a baffle that will work for this
rocket.

Quote:
> 2) I was also suprised to see a slotted body tube, with cut plywood fins,
> yet the fins only extend into the body tube about 1/8 inch. I would have
> expeected the fins to extend all the way to the motor mount for better
> structural support. Again, a very inexpensive way to provide a much more
> robust rocket. Thoughts from the experts ?

Longer tabs would be nice, but these are adequate for a rocket of this size.
If you follow my baffle instructions and add a third centering ring, you can
reinforce the inside of these tabs with more glue. One of our club members
drilled little holes thru the tab, and pinned them with toothpicks before
adding the internal epoxy. Maybe that will make you feel better.

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

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

 
 
 

Q: LOC graduator construction questions

Post by Alex Merica » Fri, 09 Oct 1998 04:00:00


Quote:

> I just rec'd the LOC Graduator kit. This is really my second rocket. The
> first being an Estes Alpha.

> A few things about the kit I found less than desirable and thought that
> I'd ask the experienced for your thoughts and suggestions:

> 1) I was suprised that the engine mount has not block, and no retaining
> clip. They suggest that the engine be wrapped with masking tape to get a

This is typical in LOC rockets (and other brands as well).
You don't need a thrust block if you use reloads, the casing has a thrust
ring built in.  If you use single-use engines you will either need to
wrap the bottom end in tape or add a thrust block to the motor tube.  I've
done it both ways and am now sold on the thrust block.  A short section of
24mm engine tube or a piece off the 29mm-24mm adapter will work.  Make sure
it is far enough in to allow you to use the longest engine you want.  You
can always add filler rings above the engine if the block is too high for
the engine you're using.

To retain the engine from blowing out the back of the rocket you can use
tape, but Kaplow Klips are better and look kooler.  A***on cap for 29mm
is described in the previous edition of Sport Rocketry.

Quote:
> 2) I was also suprised to see a slotted body tube, with cut plywood fins,
> yet the fins only extend into the body tube about 1/8 inch. I would have

Tab fins are fine for the Grad.  You can beef them up a bit by changing the
way you assemble.  First, get a third centering ring.  You will want the
assembly to look like:

       /             |
      /              |
---+----+===========+-                
   |    |           |
 --+----+-----------+-

The top two centering rings ***up against the fin tabs.  Install the top
two first, then the whole assembly in the rocket, then the fins, then the
final ring.  Make sure you glue around the tabs and rings.  You could also
add some fiberglas to the inside of the tube and on the fin fillets.

The Grad is a great kit.  Seems like it was made for a G64 reload (or was the
G64 made for it?).

Have fun!

--
Alex Mericas
NAR 62956 Level 1 Insured
President, Austin Area Rocketry Group

 
 
 

Q: LOC graduator construction questions

Post by SoAR » Fri, 09 Oct 1998 04:00:00


Your 2nd rocket??????? Dang what is up~okay do this do the thing with teh tape
it has always worked on my NCR Brute on F25-G80,it  works even with no positive
motor retention or block.....And use Epoxy (5 Min atleast) and follow
instructions well.I did this to myy LOC Aura~ i left the motor tube sticking
ouyt 1 " to tape the motor on with.It works.

~Reagan Yates~
SoAR#19
IAR#196

 
 
 

Q: LOC graduator construction questions

Post by Mighty Mi » Fri, 09 Oct 1998 04:00:00


Quote:

> I just rec'd the LOC Graduator kit. This is really my second rocket. The
> first being an Estes Alpha.

snip...

Quote:
> 2) I was also suprised to see a slotted body tube, with cut plywood fins,
> yet the fins only extend into the body tube about 1/8 inch. I would have
> expeected the fins to extend all the way to the motor mount for better
> structural support. Again, a very inexpensive way to provide a much more
> robust rocket. Thoughts from the experts ?

what *I* did...(note...the first was built from scratch...i didn't know what a
'Graduator' was at the time...fins were donated)...take the distance from the
MMT to the body tube, and scribe that onto the root of the fin. Notice where
the line intersects the leading and trailing edge...this is where you will
square up the fin (notching at the trailing edge), so it interfaces with the
centering rings. (i forget wether the kit comes with 2 or 3 rings...but mine
has 3 now.)...take the fins, rings, and MMT and dry fit them...see how it goes
together. what *I* did next was to go ahead and assemble the fin/rings/MMT...i
let this harden, and the i took the body tube and extended the slots to the
back of the tube...this allows you to slide the fin assembly into place and
glue it.

HOWEVER, you now have changed the original center of pressure, and need to do
something about that...in mine that was taken care of by taking a pack of 125
BBs and epoxying them into the nosecone. (the original was built overnight, as
i had trashed my one and only rocket in the morning). The original flew for 3
years...on motors as large as H128s...i retired that one, and took a Graduator
kit and modded as above, using the original cone. That rocket still flies
today...and I am building a fiberglass reinforced version with a 38MM mount,
and glass fins.

as to motor retention...i use reloads...but the tape method works as well.

 
 
 

Q: LOC graduator construction questions

Post by Attican1 » Sat, 10 Oct 1998 04:00:00


Quote:

>I just rec'd the LOC Graduator kit. This is really my second rocket. The
>first being an Estes Alpha.

If this is your second rocket kit I seriously suggest you put it away somewhere
and gain a lot more experience before building/flying it.  I was in the hobby
for 6 years and had many models ranging from A-D power before I got my first
Mid Power Rocket, the Aerotech Initiator, and even then I had to ask a lot of
questions and have people show me how to use the motors correctly.

Ben Romashko                              
NAR # 73422 JR                            
NIRA member                                    

"bad stuff happens to good rockets"

 
 
 

Q: LOC graduator construction questions

Post by Robert F. N » Sun, 11 Oct 1998 04:00:00


Quote:
>2) I was also suprised to see a slotted body tube, with cut plywood fins,
>yet the fins only extend into the body tube about 1/8 inch. I would have
>expeected the fins to extend all the way to the motor mount for better
>structural support. Again, a very inexpensive way to provide a much more
>robust rocket. Thoughts from the experts ?

This is typical of the lower-end LOC kits.  I strongly suggest extending
the fin tabs to the motor mount using pieces of s***1/8" ply and
fiberglassing the joint.  Every graduator I have seen has problems with the
fin joints cracking on landing.  I with LOC would fix this.

Robert F. Nee

 
 
 

Q: LOC graduator construction questions

Post by Robert F. N » Sun, 11 Oct 1998 04:00:00


Quote:
>> 2) I was also suprised to see a slotted body tube, with cut plywood fins,
>> yet the fins only extend into the body tube about 1/8 inch. I would have
>> expeected the fins to extend all the way to the motor mount for better
>> structural support. Again, a very inexpensive way to provide a much more
>> robust rocket. Thoughts from the experts ?

>Longer tabs would be nice, but these are adequate for a rocket of this size.
>If you follow my baffle instructions and add a third centering ring, you can
>reinforce the inside of these tabs with more glue. One of our club members
>drilled little holes thru the tab, and pinned them with toothpicks before
>adding the internal epoxy. Maybe that will make you feel better.

They may be adequate for flight but expect to crack the fin joints on
landing.

Robert F. Nee

 
 
 

Q: LOC graduator construction questions

Post by Dwight L. Brow » Sun, 11 Oct 1998 04:00:00


I would suggest getting 1 more centering ring, and using two of them
tointall the motor tube leaving the back end open.  Install the fins then
you can fillet the inside tabs of the fins.  Mine has never cracked a fin
joint, it even survived a ballistic reentry when the F50 failed to have an
ejection charge.
the whole body tube was crushed, but it left enough to slip a coupler in
put enough replacement tube on and.....good as new.  You can put blind nuts
on the rear ring for KaplowKlips too.

                                        Via Con Queso,
                                        D.L. Brown NAR 69453 HPR L2