Estes 'Squat Boy' - fat boy conversion

Estes 'Squat Boy' - fat boy conversion

Post by Zepp » Wed, 18 Nov 1998 04:00:00



I had an extra Fat Boy kit around and decided to create a smaller rocket out
of it. I cut the body tube at 4" from the back end, made the fins down to
about 1/2 the size of stock and cut the back end of the nose cone off
leaving 3/4" of shoulder to fit in the tube. I'm building this as light as I
can as opposed to the heavy, D powered, epoxy coated, Fat Boy conversion I
did last time out. I figure it will do very well on A engines.

Its going to be pretty darn back-heavy even with the light build. I'm sure I
need to add some weight to the nose and I've been considering using putty
type epoxy to not only add the weight but to epoxy a***eye near the nose
for attaching a recovery system. How do I determine how much weight to add
to the nose area? Will the available software help me determine the CP on a
model where it's bound to be so close the the CG?

TIA,
Jon

 
 
 

Estes 'Squat Boy' - fat boy conversion

Post by bob » Thu, 19 Nov 1998 04:00:00


Quote:

> I had an extra Fat Boy kit around and decided to create a smaller rocket out
> of it. I cut the body tube at 4" from the back end, made the fins down to
> about 1/2 the size of stock and cut the back end of the nose cone off
> leaving 3/4" of shoulder to fit in the tube. I'm building this as light as I
> can as opposed to the heavy, D powered, epoxy coated, Fat Boy conversion I
> did last time out. I figure it will do very well on A engines.

> Its going to be pretty darn back-heavy even with the light build. I'm sure I
> need to add some weight to the nose and I've been considering using putty
> type epoxy to not only add the weight but to epoxy a***eye near the nose
> for attaching a recovery system. How do I determine how much weight to add
> to the nose area? Will the available software help me determine the CP on a
> model where it's bound to be so close the the CG?

> TIA,
> Jon

Hey Jon,

Sounds like it's almost a flying saucer rather than a rocket. A
stepped-on Fat Boy.  If you don't have a computer simulation program to
model it in you might try here for one:

http://www.FoundCollection.com/

Click around for RockSim 2.0 and download the demo version.  You can't
save or print in the demo but I feel it is the easiest program out there
to learn and use.

Hmm, the more I think about your fat boy the more I like it! Did you
splay out the fins, increase the span while reducing the root and tip
chords, so they look kinda squashed?  Lemme know when you have it done
I'd love to see a picture!

Bob Fortune

 
 
 

Estes 'Squat Boy' - fat boy conversion

Post by Zepp » Thu, 19 Nov 1998 04:00:00



Quote:


>> I had an extra Fat Boy kit around and decided to create a smaller rocket
out
>> of it. I cut the body tube at 4" from the back end, made the fins down to
>> about 1/2 the size of stock and cut the back end of the nose cone off
>> leaving 3/4" of shoulder to fit in the tube. I'm building this as light
as I
>> can as opposed to the heavy, D powered, epoxy coated, Fat Boy conversion
I
>> did last time out. I figure it will do very well on A engines.

>> Its going to be pretty darn back-heavy even with the light build. I'm
sure I
>> need to add some weight to the nose and I've been considering using putty
>> type epoxy to not only add the weight but to epoxy a***eye near the
nose
>> for attaching a recovery system. How do I determine how much weight to
add
>> to the nose area? Will the available software help me determine the CP on
a
>> model where it's bound to be so close the the CG?

>> TIA,
>> Jon

>Hey Jon,

>Sounds like it's almost a flying saucer rather than a rocket. A
>stepped-on Fat Boy.  If you don't have a computer simulation program to
>model it in you might try here for one:

> http://www.FoundCollection.com/

>Click around for RockSim 2.0 and download the demo version.  You can't
>save or print in the demo but I feel it is the easiest program out there
>to learn and use.

>Hmm, the more I think about your fat boy the more I like it! Did you
>splay out the fins, increase the span while reducing the root and tip
>chords, so they look kinda squashed?  Lemme know when you have it done
>I'd love to see a picture!

>Bob Fortune

Bob,
I cut off the sweep from the trailing edge of the fins to make them
perpendicular to the body then cut 3/4" of fin from the tip chord. The fins
sort of resemble patriot fins, if that gives you an idea of the shape.

I'll download Rocksim and give it a try. Thanks for the suggestion. I'll
take a picture of Squat Boy and email it to you when its finished.

Regards,
Jon

 
 
 

Estes 'Squat Boy' - fat boy conversion

Post by bob » Thu, 19 Nov 1998 04:00:00


Quote:

> Bob,
> I cut off the sweep from the trailing edge of the fins to make them
> perpendicular to the body then cut 3/4" of fin from the tip chord. The fins
> sort of resemble patriot fins, if that gives you an idea of the shape.

> I'll download Rocksim and give it a try. Thanks for the suggestion. I'll
> take a picture of Squat Boy and email it to you when its finished.

> Regards,
> Jon

While goofing off this morning I tried it out in RockSim and I could not
get it stable. Given all the flying funnels, pyramids of death, saucers,
and happy meals that are flown in the world this should work but its by
me.  I could never get the CP behind the CG.  Maybe someone else here
can help you or you can try another simulator.  Or just build one, put
it on a nice long launch rod, with long controller leads and when no one
else around, fly it on an A.  Just be ready to duck! Better yet, lay
down on your belly before you hit the launch button. : )

Bob Fortune

 
 
 

Estes 'Squat Boy' - fat boy conversion

Post by Zepp » Thu, 19 Nov 1998 04:00:00



Quote:


>> Bob,
>> I cut off the sweep from the trailing edge of the fins to make them
>> perpendicular to the body then cut 3/4" of fin from the tip chord. The
fins
>> sort of resemble patriot fins, if that gives you an idea of the shape.

>> I'll download Rocksim and give it a try. Thanks for the suggestion. I'll
>> take a picture of Squat Boy and email it to you when its finished.

>> Regards,
>> Jon

>While goofing off this morning I tried it out in RockSim and I could not
>get it stable. Given all the flying funnels, pyramids of death, saucers,
>and happy meals that are flown in the world this should work but its by
>me.  I could never get the CP behind the CG.  Maybe someone else here
>can help you or you can try another simulator.  Or just build one, put
>it on a nice long launch rod, with long controller leads and when no one
>else around, fly it on an A.  Just be ready to duck! Better yet, lay
>down on your belly before you hit the launch button. : )

>Bob Fortune

Bob,
This is probably a dumb question but does Rocksim give you the option to
keep adding more weight to the nose? If it does do you get to say how far up
the nose it gets added? I'm epoxying weight into the point of the nosecone
and I'm wondering if the program assumes the weight will be behind the
shoulder? Actually would this even matter?  B)

I'll play with Rocksim and Vcp which I also downloaded today and see if it
helps.

Thanks for trying, 'preciate it.

Regards,
Jon

 
 
 

Estes 'Squat Boy' - fat boy conversion

Post by Chris Taylo » Thu, 19 Nov 1998 04:00:00


Yeah and after it pins you to the ground we will come over and take a
picture before releasing you :-)

Good Idea though I may make a literal Squashed fat boy or another design
rocket in squash form sounds neat :-)

Chris
http://www.nerys.com/rocketry/


Quote:


>> Bob,
>> I cut off the sweep from the trailing edge of the fins to make them
>> perpendicular to the body then cut 3/4" of fin from the tip chord. The
fins
>> sort of resemble patriot fins, if that gives you an idea of the shape.

>> I'll download Rocksim and give it a try. Thanks for the suggestion. I'll
>> take a picture of Squat Boy and email it to you when its finished.

>> Regards,
>> Jon

>While goofing off this morning I tried it out in RockSim and I could not
>get it stable. Given all the flying funnels, pyramids of death, saucers,
>and happy meals that are flown in the world this should work but its by
>me.  I could never get the CP behind the CG.  Maybe someone else here
>can help you or you can try another simulator.  Or just build one, put
>it on a nice long launch rod, with long controller leads and when no one
>else around, fly it on an A.  Just be ready to duck! Better yet, lay
>down on your belly before you hit the launch button. : )

>Bob Fortune

 
 
 

Estes 'Squat Boy' - fat boy conversion

Post by bob » Thu, 19 Nov 1998 04:00:00


Quote:

> Bob,
> This is probably a dumb question but does Rocksim give you the option to
> keep adding more weight to the nose? If it does do you get to say how far up
> the nose it gets added? I'm epoxying weight into the point of the nosecone
> and I'm wondering if the program assumes the weight will be behind the
> shoulder? Actually would this even matter?  B)

> I'll play with Rocksim and Vcp which I also downloaded today and see if it
> helps.

> Thanks for trying, 'preciate it.

> Regards,
> Jon

Hey Jon,

I'm strictly a RockSim user and I don't profess to know all there is to
know about this program. I probably use about 15% of what it is capable
of doing.  With that in mind I hope someone else more able than I will
help you get this to fly properly for it could be fun.

However, what I can tell you might be better dealt with via email.  Drop
me a line.

Bob

 
 
 

Estes 'Squat Boy' - fat boy conversion

Post by Andy En » Fri, 20 Nov 1998 04:00:00


Hello RD #1,

Quote:

> Sharing the wisdom of the ages with those of us reading



<ctrl-x>

Quote:
> >else around, fly it on an A.  Just be ready to duck! Better yet, lay
> >down on your belly before you hit the launch button. : )

> Lying down is a bad idea, Bob.  If you are *at all* concerned about a
> rocket's stability, the *last* place you want to be is lying down when
> it launches.  If you are standing up and paying close attention when
> an errant rocket comes your way, you have at least a fighting chance
> to move a foot or two to the left or right, and have it buzz past you.
> Lying down, you have *no* chance to avoid it if it's coming towards
> you.

<ctrl-x>

Quote:
>  - Rick "Heads up!"***inson

Now you wouldn't be speaking from *experience* here, would you?  {8}^)

Andy

p.s.   After reading the above, I had flashbacks of that Black Rock
video where spectators were scrambling for cover under the u-haul as
flaming propellant rained from the sky...   <ouch!>  {8}^D

 
 
 

Estes 'Squat Boy' - fat boy conversion

Post by Zepp » Fri, 20 Nov 1998 04:00:00


Quote:

>Hello RD #1,


>> Sharing the wisdom of the ages with those of us reading


><ctrl-x>

>> >else around, fly it on an A.  Just be ready to duck! Better yet, lay
>> >down on your belly before you hit the launch button. : )

>> Lying down is a bad idea, Bob.  If you are *at all* concerned about a
>> rocket's stability, the *last* place you want to be is lying down when
>> it launches.  If you are standing up and paying close attention when
>> an errant rocket comes your way, you have at least a fighting chance
>> to move a foot or two to the left or right, and have it buzz past you.
>> Lying down, you have *no* chance to avoid it if it's coming towards
>> you.

><ctrl-x>

>>  - Rick "Heads up!"***inson

>Now you wouldn't be speaking from *experience* here, would you?  {8}^)

>Andy

>p.s.   After reading the above, I had flashbacks of that Black Rock
>video where spectators were scrambling for cover under the u-haul as
>flaming propellant rained from the sky...   <ouch!>  {8}^D

Hmmm, maybe I'll let my cousin Bill launch the first flight of Squat Boy.
He's always bugging me to let him press the button.

"Now just wait one minute Bill, I've always wanted to see what a launch
looks like from INSIDE the van."

:^)
Jon

 
 
 

Estes 'Squat Boy' - fat boy conversion

Post by Alan W. Holm » Fri, 20 Nov 1998 04:00:00



Quote:

>If you don't have a computer simulation program to
>model it in you might try here for one:

>http://www.ApogeeRockets.com/

>Click around for RockSim 2.0 and download the demo version.  You can't
>save or print in the demo but I feel it is the easiest program out there
>to learn and use.

I don't know about RockSim, but the simulation programs I'm familiar
with use the Barrowman equations.  IIRC one of the *assumptions* in
the Barrowman equations is a length-to-diameter ratio of 10-1.  If
this assumption is wrong, the results of the sim are in doubt.  

I've always figured that the further away from the 10-1 ratio the
rocket is, the further away from the correct CP the program would
produce (no scientific reason to believe this, just my guess).  Given
this, I wouldn't expect a sim to be very useful for a "Squat Boy".
Isolated testing with long rod on a windless day is definitely called
for.

Alan Holmes

 
 
 

Estes 'Squat Boy' - fat boy conversion

Post by Tom Binfor » Fri, 20 Nov 1998 04:00:00


Quote:

> >p.s.   After reading the above, I had flashbacks of that Black Rock
> >video where spectators were scrambling for cover under the u-haul as
> >flaming propellant rained from the sky...   <ouch!>  {8}^D

> Ouch is right!  Yikes!  Is this video online anywhere?

LDRS XIV / BALLS 5. Rocketman Videos has the best coverage. (It was Ky's
rocket.) Brief coverage in Earl's (Point 39 Productions) LDRS XIV video.
Both of these videos are still available for purchase.
Tom