Dynastar Orion Transport

[billeblurzz]

This is the second of the DYNASTAR kits that I am building. The ORION TRANSPORT uses the same body tube, nose cone, and engine mounts as the SNARKY. Pretty simple construction....only a cardstock engine nozzle to be built. I also added round airfoils to the leading edges of the fins.

 

[billeblurzz]

Even though it uses many of the same parts, it seems like a much smaller rocket....much less wing area. Will be interesting to see the different flight characteristics!

 

[billeblurzz]

Rear shot showing cardstock nozzle stiffened with CA, and filleted fins waiting to be rubbed with Fill 'n' Finish and coated with sanding sealer.

 

You should write a book on building and finishing model rockets. Everytime I see pictures of your rockets they look like they are from the catalog. Keep up the good work and keep sharing with us.

Brian

 

[billeblurzz]

Here is the ORION TRANSPORT after filling balsa with Fill 'n' Finish, one coat of Minwax Sanding Sealer, sanding between each step, priming with Kilz primer, sanding down again, and spraying with Krylon paints. Decals were applied and nozzle area was highlighted by hand with red Humbrol like the Saturn boosters!

 

[billeblurzz]

Beautiful lines...has an X-plane look to it! Nozzle has been stiffened with CA and several layers of finish...though landing damage could occur, the HUGE 32" chute should help! I can't imagine an F21 in this stubby-winged thing....may take off "like a rocket!"

 

[billeblurzz]

Even though decals are self-adhesive (STICK-ON), they are very nice!

 

[billeblurzz]

Instead of the suggested black belly color...went with Navy Blue picked up from some of the decals...gave a NASA F-104 like look to it!

 

[billeblurzz]

I just might have to get the other two kits even though these were the only ones I was interested in initially. Classic good lines!! I guess all that's left is a launch report!

 

[slim_t]

Man. Have you ever built an ugly rocket?
Ugly rockets can be fun too you know, like the ACME Spitfire.

Seriously, I'm gonna have to drive over there one day and take a walk through the museum. Do you charge admission?

Tim

 

[billeblurzz]

Thanks Slim, you are always welcome to head this way....only BRING SOME ROCKETS....if there is such a thing as a museum, it most certainly is a FLYING one!!! My town is also the home of Mr. REBAR ROCKETRY...this fellow is on the ball and seems to be putting together one of the best rocketry supplies around! If he gets any bigger, I may see if I can go work for him! CHECK HIM OUT!!

 

[billeblurzz]

Today I went out to see how this cool little rocket flies! As built, the center of gravity was right at the middle of the body tube under the forward fins. I was a little uneasy about this mark and since it would be hard to swing test in this position, I added some clay nose weight to bring the center of gravity just past the forward fins. I ended up with about 2 oz. of weight. This brought the weight up to about 8 oz. without the motor. It would swing test just right at this weight. This also took care of any shifting of the chute material during flight!

 

[billeblurzz]

Even though I used a D12-3 in the SNARKY, I thought this ORION might use the recommended D12-5 since it was sleeker with less draggy fins. Here is liftoff on a D12-5:

 

[billeblurzz]

The choice of the D12-5 was a little long for the delay...but that was NOT the problem. The boost was absolutely beautiful...quick and straight...but there was separation at ejection. The body went into a flat spin separated from the nose and chute. The chute never opened with the nose. At first I thought the kevlar cord had burned into...since it was tied to the motor mount thrust ring close to the motor. I have always been concerned about this method of attachment....but upon inspection, the ejection charge completely BLEW OUT the thrust ring! The thrust ring is right at the top of the motor tube...anyone building this kit needs to take care to make sure of sufficient glue since there is not much surface area there...maybe a LONGER motor tube is needed. The ring looks like it FAILED also. Since the chute never opened, it was not the shock of recovery that caused it to fail. This shows that if the thrust ring happens to fail, you loose everything. The old Estes method of attachment maybe is time-tested!

 

[billeblurzz]

Even though I was upset with the separation, the body tumbled all the way to the ground and suffered NO DAMAGE AT ALL!!!
AMAZING!!!....it just fell flat. I don't think I will ever need to launch on an E...keeping it in sight is neat because after burnout it kinda tried to fly like a plane! A new thrust ring at the location for just Estes D motors will leave more surface area ahead of the thrust ring for sufficient glue so maybe it won't blow out again! I will go back to the Estes shock cord attachment....maybe. I like this kit and the SNARKY!

 

[BobH48]

The last two D12-5's that I used had what seemed to be a more powerful ejection charge that what I had used before.

They had a manufacturing date of 09 06 02.

I thought I read in a different thread about extra powerful ejection charges in some motors.

 

[cls]

my Orion's cord & thrust ring have come out a couple times. I don't think it is the motor, somehow there is something preventing the glue from working on that MMT.

I too am going to change mount, maybe just glue the string along the BT way deep in there.

 

[Stymye]

thats a bad location to tie the shockcord even if it is kevlar
still,the ejection should easily blow thru the ring, it looks more like the cord pulled it out.. I wonder how long are the shock cords on these dynastars?

 

[cls]

the dynastar kits have a really long kevlar cord. I think it is 10' long, 300# cord. really nice. and 32" parachutes, somewhat overkill but fun anyways.

 

Originally posted by billEblurzz
The choice of the D12-5 was a little long for the delay...but that was NOT the problem. The boost was absolutely beautiful...quick and straight...but there was separation at ejection. The body went into a flat spin separated from the nose and chute. The chute never opened with the nose. At first I thought the kevlar cord had burned into...since it was tied to the motor mount thrust ring close to the motor. I have always been concerned about this method of attachment....but upon inspection, the ejection charge completely BLEW OUT the thrust ring! The thrust ring is right at the top of the motor tube...anyone building this kit needs to take care to make sure of sufficient glue since there is not much surface area there...maybe a LONGER motor tube is needed. The ring looks like it FAILED also. Since the chute never opened, it was not the shock of recovery that caused it to fail. This shows that if the thrust ring happens to fail, you loose everything. The old Estes method of attachment maybe is time-tested!

I had the same problem with the Dynastar Rising Star at last month's launch in Manchester. Attached is a pic of the nose cone lawn dart...

As with your Orion, the body suffered no damage.

 

[billeblurzz]

Wow, others have had the same problem. I don't think the cord pulled out the thrust ring....because the chute never unfurled. You could see in flight that at the moment of ejection....every thing blew out at once! I just believe there needs to be a longer motor tube so you can build up a glue "stop" ahead of the thrust ring!

 

[JRThro]

Originally posted by billEblurzz
Wow, others have had the same problem. I don't think the cord pulled out the thrust ring....because the chute never unfurled. You could see in flight that at the moment of ejection....every thing blew out at once! I just believe there needs to be a longer motor tube so you can build up a glue "stop" ahead of the thrust ring!

Is there any chance that the momentum of the nose cone, once it blew off the front end of the rocket, pulled the thrust ring out?

Just a thought.

 

[cydermaster]

I'm in the beginning stages of building my Orion Transport. Thanks to this thread, I'll try popping a small blob of 30min epoxy round the top of the thrust ring (I've biult my mmnt, but not glued it inside the bt yet).

I'm wondering if its worth shortening the Kevlar by about 3ft, and substituting some elastic shock cord?

 

[Fore Check]

I have to agree with the idea that this is a poor kevlar attachment method.

I certainly would NOT attach the kevlar to the thrust ring.

The method that I always use (except on clusters with a nice, stout plywood centering) is to tie the kevlar to the exterior of the engine mount tube, right behind the forward-most centering ring, and then pass the kevlar forward in the seam between that centering ring and the motor tube. You may have to cut a *small* notch in the inside of that centering ring to allow for the kevlar to pass through, but that's no big deal.

What I do is tie a loop knot in the kevlar, and then make a slip knot by passing the remainder of the thread through the tied loop (thus creating a "second" loop that collapses on itself when you pull on the string.) Put that around the motor tube, glue on centering ring, and pull tight. Fillet with a dab of CA or epoxy.

Here's a quick sketch of what I mean - in the sketch, the kevlar is not "pulled tight" against the centering ring for clarity. This is easily done after the ring is installed, but before the glue sets completely.

 

[JRThro]

Originally posted by Fore Check
I have to agree with the idea that this is a poor kevlar attachment method.

I certainly would NOT attach the kevlar to the thrust ring.

The method that I always use (except on clusters with a nice, stout plywood centering) is to tie the kevlar to the exterior of the engine mount tube, right behind the forward-most centering ring, and then pass the kevlar forward in the seam between that centering ring and the motor tube. You may have to cut a *small* notch in the inside of that centering ring to allow for the kevlar to pass through, but that's no big deal.

What I do is tie a loop knot in the kevlar, and then make a slip knot by passing the remainder of the thread through the tied loop (thus creating a "second" loop that collapses on itself when you pull on the string.) Put that around the motor tube, glue on centering ring, and pull tight. Fillet with a dab of CA or epoxy.

Here's a quick sketch of what I mean - in the sketch, the kevlar is not "pulled tight" against the centering ring for clarity. This is easily done after the ring is installed, but before the glue sets completely.

Fore Check,

That looks like a really good attachment method, compared to attaching the Kevlar to the engine block. The last 3 Quest kits I've built, or am in the process of building, use the attachment-to-engine-block method. Although now that I think of it, they are 19 mm ID BT's w/ 18 mm motor tubes, so there *aren't* any centering rings (duh). In designs where there are centering rings, though, I like your method.

What about using some elastic cord for the last few feet of the shock cord instead of Kevlar, as someone else suggested? That should reduce the shock on the attachment point when the nose cone reaches the end of its travel after ejection.

As an aside, I'd like to note that the Apogee newsletter #95 suggests a method of shock cord mounting that's *very* similar to yours as a means of motor retention for minimum diameter rockets, except that the shock cord isn't glued to anything. When the nose cone ejects, the loop in the shock cord pulls tight and holds the motor in. On re-reading the article, he might be using this as a backup for masking tape motor retention.

 

[Stymye]

You could see in flight that at the moment of ejection....every thing blew out at once!

thats what made me think of the cord pulling because during ejection, the motor is thrusting rearward and there is no pressure against the ring..if the ring joint was weak it would give out during the boost phase rather than during coasting or ejection..but it also seems like a 10' cord would be plenty..

well atleast is repairable!

 

[slim_t]

Just some thoughts here.
The pic of the thrust ring looks as if it were ripped from its skin, as if a thin layer remained glued to the motor tube and the rest was ripped out. If that's the case, then a good build up of glue on top should solve that.

Someone also mentioned the momentum of the heavier nose. I think this could be a possibility if the ejection charge is strong enough. But if the shock cord is 10' long, it seems it would be ok. Maybe a length of elastic would help.

Anyway, I'm glad you still recovered the rocket ok. Did you get the nose cone, too?

Tim

 

[billeblurzz]

Thanks for the replies! The nose cone with chute attached lawn darted into the ground! The pictures of the parts at the end of the thread show everything after recovery and the only damage was to the thrust ring. There is left glued in the motor tube part of the outside layer of the thrust ring...so it seems it was really a failure of the ring itself! The outside of the ring was notched so the kevlar cord would pass between the ring's outside and the inside of motor tube. Breaking this outside paper layer seems to have allowed the ring to fail with the heat of ejection by peeling or unraveling! Anyway mounting your whole recovery system to this weak link in hindsight seems asking for trouble! I sometimes don't even understand why I do things....since I use epoxy mostly throughout construction, I just use wood glue on centering ring to motor tubes....and wood glue to install thrust rings! I guess by laziness I don't go ALL the way in these steps too! I still believe a longer motor tube would give more surface area ahead of the thrust ring for a better glue STOP! The epoxy filling the cavity in front of the thrust ring IS a GOOD IDEA!!! You would think MR. EPOXY (me) would have done that!!!

 

[cydermaster]

Did anybody else find the die-cutting on the little-triangle-wingtip-things shocking?

I've ended up having to cut a new one from the spare balsa, because one of the pre-cut ones was too badly 'squashed' by the cutter.

There is alot of spare balsa to choose from, PLUS Dynastar has had the sense to put in a fin template sheet, so cutting a new one wasn't that much of a bind.

 

[slim_t]

Originally posted by billEblurzz
The outside of the ring was notched so the kevlar cord would pass between the ring's outside and the inside of motor tube. Breaking this outside paper layer seems to have allowed the ring to fail with the heat of ejection by peeling or unraveling.

This is a pretty interesting thought. I have a model I did this with and have flown it 4 times on A-C motors without any trouble so far.

Right now I am working on a Semroc Sky Hook and SLS Sky Hook. Both use this method, but without notching the ring. On the small one I notched the ring anyway to make it fit better. On the larger SLS the fit is a bit loose so I didn't notch it. I wonder how they'll perform?

You know, it could just be one of those things, where any little thing could have caused it or prevented it.
But I think your thought above is probably the cause, and more glue on top will probably prevent it. And instead of just building to hold D's, you could just give yourself 1/8" at the top of the ring for glue, and still use E's. They'd just stick out that extra 1/8".

Tim