Larger fins on Mean Machine

Larger fins on Mean Machine

Post by Joel Leno » Tue, 14 May 1996 04:00:00



Recently got a Mean Machine kit, and the fin stock appears rather thin
(0.095") for such a large rocket.  In fact, the fins seem rather small in
proportion to the overall size and length.

I've read a recent article here about reinforcing these fins with modeling
tissue, and am planning on doing just that.

Does anyone see a problem with 1/8" fins?  How about enlarging the fin size?  
I would be surprised if stability would be a problem with a slight increase in
fin size.

Also, does this 24" chute need a vent hole or would the resulting descent be
too fast?

Thanks.
Joel Lenoir

 
 
 

Larger fins on Mean Machine

Post by Paul Hamilt » Tue, 14 May 1996 04:00:00


On May 13, 1996 14:57:34 in article <Larger fins on Mean Machine>,

Quote:

>Does anyone see a problem with 1/8" fins?  How about enlarging the fin
size?  
>I would be surprised if stability would be a problem with a slight
increase in  

>fin size.

Enlarging the fins would actually increase static stability.  For a heavy
model like the Mean, that could make it more wind sensitive.  Also, larger
fins are more apt to break.

Thicker fins would slightly increase static stability without a
corresponding increase in weathercocking tendency.

I think vent holes are generally a good idea.
--
Paul Hamilton
Samis & Hamilton
Aviation and Airport Consultants
11706 Smoketree Road
Potomac, MD 20854
(301) 299-3573

 
 
 

Larger fins on Mean Machine

Post by PaulDimi » Wed, 15 May 1996 04:00:00



Quote:
(Joel Lenoir) writes:

>Also, does this 24" chute need a vent hole or would the resulting descent
be
>too fast?

I wonder about that chute as well.  I've only flown my Mean Machine once
so far.  I used the 24" chute with no spill hole and a D-12.  The rocket
drifted pretty far since it was caught in a breeze.  Almost lost it.  I'm
tempted to try a spill hole or perhaps the 18" chute.  Any experiences out
there on either alternative for the Mean Machine?

Paul.

Fly Baby Fly!

 
 
 

Larger fins on Mean Machine

Post by Hawk_Ds » Wed, 15 May 1996 04:00:00


Quote:


> (Joel Lenoir) writes:

> >Also, does this 24" chute need a vent hole or would the resulting descent
> be
> >too fast?

> I wonder about that chute as well.  I've only flown my Mean Machine once
> so far.  I used the 24" chute with no spill hole and a D-12.  The rocket
> drifted pretty far since it was caught in a breeze.  Almost lost it.  I'm
> tempted to try a spill hole or perhaps the 18" chute.  Any experiences out
> there on either alternative for the Mean Machine?

> Paul.

> Fly Baby Fly!-------------------------------------------------------------

Paul, in the past, I have ALWAYSed used a spill hole in ALL my chutes. When
you cut spill holes in the chute, it helps keep the rockets from "swinging"
as they desend. The way I used to check for the right desend rate, was to
roll newspapers to the same weight as the rocket, tie the chute to it, and
toss it off somthing high (monky bars at a school maby), or throw it and
watch what happend. Make the spill hole small, and make it bigger with each
test untill your happy. Keep in mind that I have done this only with plastic
chutes. Nylon or cloth would be alittle tricky, because you would have to sow
the holes so that they wont rip.

Hope that helps.

[ sigfile.txt < 1K ]
Hawk_Dsl...NAR# 65336. NOVAAR #205

"We Need A Bigger Boat..."

 
 
 

Larger fins on Mean Machine

Post by Wally Wilki » Thu, 16 May 1996 04:00:00


Quote:

>Recently got a Mean Machine kit, and the fin stock appears rather thin
>(0.095") for such a large rocket.  In fact, the fins seem rather small in
>proportion to the overall size and length.
>I've read a recent article here about reinforcing these fins with modeling
>tissue, and am planning on doing just that.
>Does anyone see a problem with 1/8" fins?  How about enlarging the fin size?  
>I would be surprised if stability would be a problem with a slight increase in
>fin size.
>Also, does this 24" chute need a vent hole or would the resulting descent be
>too fast?

Enlarging the fins will encrease the drag.  This will actually
increase the stability of the rocket.  Methods of increasing the
stability of a rocket:
1.  Increase nose weight
2.  Increase rocket length
3.  Increase fin area
4.  Increase number of fins (at back of rocket)  Fins up forward
decrease stability.

Increased drag will mean that the rocket doesn't fly as high.

Chute size is dependent on a number of things.  
1.  The altitude you fly at (not a big problem for most of us <g>)
2.  The stability of the rocket when the chute is deployed.
3.  The weight of the rocket.
4.  Construction of the rocket.

Optimal descent rate is around 20 ft/sec.  This provides minimum drift
and minimum landing damage.  YMMV

I would say that if you reinforce the fins, that it would be ok to add
the vent hole to the chute, just don't get to carried away.

Wally Wilkins
NAR #64578 SR
TRA # 4428
NERO $197
All opinions are my own, and worth what you paid for them.

 
 
 

Larger fins on Mean Machine

Post by Chris Ge » Thu, 16 May 1996 04:00:00


i've mod'ed my mean machine a little bit :-)

1 - used the tail cone from the sentinel(?) with a little bit of
judicious sanding to fit(looks pretty cool now)
2 - reinforced the fins with tissue and epoxy
3 - added a stub to the fins for ttw to the MM
4 - cut about 8 inches off the top of the airframe
due to a snapped shock cord and the resulting ding
at the top end
5 - added some clay to the nose(just a ***y bit w/epoxy)
6 - mounted new shock cord(wide, flat kind from loc kits)
through a slit in the airframe belew the nose cone
shoulder, covered outside with paper(sort of like
fixing sheetrock) to smooth it out.  this shock cord
is very long, at least three feet long.
7 - using a 12 inch chute with no hole.  the rocket sort of
flies horizontally on its way down.

i'm just sorry i haven't been very scientific about
these mods, they were sort just thrown together

chris

Quote:


>(Joel Lenoir) writes:
>>Also, does this 24" chute need a vent hole or would the resulting descent
>be too fast?
>I wonder about that chute as well.  I've only flown my Mean Machine once
>so far.  I used the 24" chute with no spill hole and a D-12.  The rocket
>drifted pretty far since it was caught in a breeze.  Almost lost it.  I'm
>tempted to try a spill hole or perhaps the 18" chute.  Any experiences out
>there on either alternative for the Mean Machine?

>Paul.
>Fly Baby Fly!

--
Christopher W. Gee   !  Walt Disney Feature Animation

voice (818)560-9222  !  500 South Buena Vista Street,
  fax (818)560-8291  !  Burbank, CA 91521-4823
 
 
 

Larger fins on Mean Machine

Post by Jerry Irvi » Thu, 16 May 1996 04:00:00



Quote:


> (Joel Lenoir) writes:
> >Also, does this 24" chute need a vent hole or would the resulting descent
> be
> >too fast?

> I wonder about that chute as well.  I've only flown my Mean Machine once
> so far.  I used the 24" chute with no spill hole and a D-12.  The rocket
> drifted pretty far since it was caught in a breeze.  Almost lost it.  I'm
> tempted to try a spill hole or perhaps the 18" chute.  Any experiences out
> there on either alternative for the Mean Machine?

Up to a 15% (of total area) spill hole the desent rate will not decline
much but the drift dispersion will.  Above that it might.  The more common
and sensible method is to "***up" the chute by "reefing the shrouds"
and placing a piece of tape about halfway up the shrouds.

Just Jerry

"It's not how fast you go that determines how far you get"

--

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

 
 
 

Larger fins on Mean Machine

Post by PaulDimi » Thu, 16 May 1996 04:00:00


Quote:

>Paul, in the past, I have ALWAYSed used a spill hole in ALL my chutes.
When
>you cut spill holes in the chute, it helps keep the rockets from
"swinging"
>as they desend. The way I used to check for the right desend rate, was to
>roll newspapers to the same weight as the rocket, tie the chute to it,
and
>toss it off somthing high (monky bars at a school maby), or throw it and
>watch what happend. Make the spill hole small, and make it bigger with
each
>test untill your happy. Keep in mind that I have done this only with
plastic
>chutes. Nylon or cloth would be alittle tricky, because you would have to
sow

>the holes so that they wont rip.

>Hope that helps.

To all who have shared their ideas in response to my queries, THANK YOU!
All responses help.  Even those that contradict others in the thread.
From all responses, I put together the puzzle that is rocketry.  Thanks!

Paul.

Fly Baby Fly!

 
 
 

Larger fins on Mean Machine

Post by Russell Durk » Fri, 17 May 1996 04:00:00


 I have seen a "Mean Machine" that was
about 12-16 inches long fly on D12s with
no stability problems.  I guess it really wasnt
all that mean anymore but is sure was stable
Think about the Estes Black Brant....kind of
the same length. (But it has bigger fin area...)

YMMV

Russ

 
 
 

Larger fins on Mean Machine

Post by Robert Maste » Fri, 17 May 1996 04:00:00



Quote:

>(Joel Lenoir) writes:
>>Also, does this 24" chute need a vent hole or would the resulting descent
>be
>>too fast?
>I wonder about that chute as well.  I've only flown my Mean Machine once
>so far.  I used the 24" chute with no spill hole and a D-12.  The rocket
>drifted pretty far since it was caught in a breeze.  Almost lost it.  I'm
>tempted to try a spill hole or perhaps the 18" chute.  Any experiences out
>there on either alternative for the Mean Machine?

I have used an 18" chute with spill hole, with no damage, but I found
that the drift was still quite bad. I then tried a long (20') streamer,
but that was not quite enough drag, and I broke a couple of fins.

For my next flight (whenever that is :-( ), I will be using a 12" chute,
and some streamer tape.

-Rob
(ARA 47-2)
--

"When I was young, I promised myself that I would die doing something noble,
 brave, and futile...Maybe it was not such a hopeless dream after all!"
- Londo (Babylon 5 "A Voice in the Wilderness")            <*>

 
 
 

Larger fins on Mean Machine

Post by SteveB71 » Fri, 17 May 1996 04:00:00


Quote:
>Recently got a Mean Machine kit, and the fin stock appears rather thin
>(0.095") for such a large rocket.  In fact, the fins seem rather small in
>proportion to the overall size and length.
>I've read a recent article here about reinforcing these fins with
modeling
>tissue, and am planning on doing just that.
>Does anyone see a problem with 1/8" fins?  How about enlarging the fin
size?  
>I would be surprised if stability would be a problem with a slight
increase in
>fin size.
>Also, does this 24" chute need a vent hole or would the resulting descent
be
>too fast?

I have a Mean Machine that is dead stock exept for an 18 inch chute. The
stability is not a problem. I have chad staged it with a D12-0 to D12-7.
It goes almost out of sight and lands a resonable distance away. I also
have had no problem with fin breakage but have had them tear from the body
tube once or twice, even with epoxy fillits.

Steve Blandford

 
 
 

Larger fins on Mean Machine

Post by Andrew Sander » Fri, 17 May 1996 04:00:00


Quote:

> Up to a 15% (of total area) spill hole the desent rate will not decline
> much but the drift dispersion will.  Above that it might.  The more common
> and sensible method is to "***up" the chute by "reefing the shrouds"
> and placing a piece of tape about halfway up the shrouds.

--
It's a bit out of my knowledge base, but Dave Fox (MBR) gave me a
severe lashing for telling this to someone once.  If I recall correctly (I
usually try to forget things like lashings, at least of me), he said that
a spill hole will reduce the oscillation (driven by air dumping out
around the perimeter), but can actually increase the lift, and
correspondingly the drift!

A better solution would be to go to an X-Form chute.  From the
ones I've seen, and the couple I use, it is amazing how they come
almost straight down in breezy conditions.

-----------------------------------------------------
|Andrew Sanders     | Mind like a steel trap.  Old, |
|Boeing Employees   | rusty, and prone to springing |
|Model Rocket Club  | shut without provocation!     |
|---------------------------------------------------|


-----------------------------------------------------

 
 
 

Larger fins on Mean Machine

Post by Jerry Irvi » Sat, 18 May 1996 04:00:00



Quote:


> > Up to a 15% (of total area) spill hole the desent rate will not decline
> > much but the drift dispersion will.  Above that it might.  The more common
> > and sensible method is to "***up" the chute by "reefing the shrouds"
> > and placing a piece of tape about halfway up the shrouds.

> It's a bit out of my knowledge base, but Dave Fox (MBR) gave me a
> severe lashing for telling this to someone once.  If I recall correctly (I
> usually try to forget things like lashings, at least of me), he said that
> a spill hole will reduce the oscillation (driven by air dumping out

Correct.

Quote:
> around the perimeter), but can actually increase the lift, and

Correct.

Quote:
> correspondingly the drift!

Not necessarily.
In fact my personal experience is that with a spill hole the drift is
reduced.  However this might be offset by the fact that on a warm breezy
day lift and thermal catching is increased.

Quote:
> A better solution would be to go to an X-Form chute.  From the

Correct.

Quote:
> ones I've seen, and the couple I use, it is amazing how they come
> almost straight down in breezy conditions.

Included in alot of U.S. Rockets kits! I believe the first manufacturer to
widely include them.

Quote:
> |Andrew Sanders     | Mind like a steel trap.  Old, |

So I guess I will be slightly less severely lashed than you were.

Jerry

--

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