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Tube fins with engines inside.

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Shade

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This can be launched with a central 24 x 90mm engine the outboard tube
fins/engines can be loaded with 18 x 75mm engines.

The "Look" was was going for was old school jet engine. The MMT inside
the tube fins are attached with longintudinal struts and not centering rings.
this allows for air flow.

The engines are not canted toward the SG so when I do try a four engine
launch if any of the outboard engines do not light it could get interesting.
First flights will be on a single D and E engines.

I need to take some better pics to show the construction.

Tube fin cluster 1.JPG


Tube fin cluster 2.JPG
 
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powderburner

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OK, these comments are "qualitative" and not "quantitative" (that is, I didn't do any calculations or anything, just using the ol' eyeball), and not intended as criticism, but...

I am more than a little nervous that your "tube" fins are not going to act very much like tube fins (or any other kind of fins) with as much blockage as you are showing. I think you would best off to run a stability analysis using only the flat-panel conventional fins and not count on those tube-fin-esque bodies to contribute much to stability.

Other than that, the design does indeed look cool.

My two cents (which you didn't ask for)
 

FatBoy

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Nice job, Shade. That is sweet!
 

jj94

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That looks very cool. However, I express the same concerns as powder. Will there be enough airflow through the available space to provide sufficient stabilty?
 

Shade

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I had the very same concern and that is why it is at 40" OAL and not my
original ~22" plan. I did have to add nose weight with 3 C6-0 and an E9-8
loaded up with a swing test. I had no luck in getting this built in Rocksim V8,
does anyone know if this could be built in V8 or V9?

I am going to determine the final mass needed after I have it all finished up.
 

asm109

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Great minds think alike!!!

Here are some pix of a rocket I built last year. The engine pods are constructed as you did with one difference. I used a piece of air foil shaped Aluminum tubing to duct the ejection charges from the engine pods into the center tube. This is visible as the forward fin that connects the pod to the main body tube. I tried to make it fly without any external fins. I could not get it the pass a swing test. I ended up with the fairly large fins to make it pass. Even then, I keep a couple of burnt engines up in the payload compartment as insurance.
For scale the tip of the nosecone is 50 inches above the floor. The main Bodytube is BT-60, the payload and bottom section are BT-70

The center engine in a 24 mm tube and I usually run a D11-P in there and C6-5's in the 3 outers. It flys great!!

IMG_1574.jpg


IMG_1577.jpg
 

Shade

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Ducting the ejections charges that is cool.

My outboards I put a heavy coat of epoxy to protect the
nosecones which are balsa. You can see the reflection of
the epoxy in the one photo.

The only thing I really hate living in the boonies is dial up!!!!!
It sucks.

P1010001.JPG


P1010002.JPG


P1010003.JPG


P1010004.JPG


P1010005.JPG
 
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Shade

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My plan is to have one permanent mass epoxied to the
base of the NC, and a add on mass. The add on will
compensate for the four engine configuration and without
the add on it will be balanced for single engine flights.
 
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El Cheapo

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It should fly fine. I built this one out of paper towel tubes and toilet paper tubes. It flies on three 18mm motors and a 24mm Sustainer. It moderately passed a swing test w/a ton of nose weight. It probably could have flown on half the nose weight but I didn't have Rocksim and just wanted to be sure.

First flight was absolutely beautiful. Second flight only lit the center booster and one side pod. It took off straight but staged horizontal. You can guess what happened next.

TomS_2Stage.jpg
 

Diosces

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Both look like fantastic builds! Definitely some info that I can use in my current project
.. past several months I have been designing a similar concept but with 7.5 " dia body central 98 mm engine and 38 mm 'outrigger' motor outboards, but those will be minimum diameter

Her's the link for discussion regarding honeycomb fin materials Cerberus honeycomb fin discussion

very nice and thanks for sharing the photo's
 

kramer714

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Do you care if there is airflow in the tubes?

IF these were totally blocked I think they would add a lot of base drag, shifting the dynamic center of pressure aft. Not great if you are trying to go high, good for stability.

just a thought....
 

Shade

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Do you care if there is airflow in the tubes?
Not really, there will be some flow.

IF these were totally blocked I think they would add a lot of base drag, shifting the dynamic center of pressure aft. Not great if you are trying to go high, good for stability.

just a thought....
I was going for "look" and fun with this not performance.
 

nukemmcssret

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I do not know what trouble you are having with the design, but I will guess the fins part. First go to the custom fins. You have to build each fin one at a time. Select custom fins and pick any design, and in plan points design your fin. Go to general and pick one fin in a set. Now you have to position the fin where you want it on your rocket. Next with your fin selected, look at the add new components. You will see pod is the only selection in black. Select it and follow the directions on the screen. You can then select the pod and select a body tube and customize it the way you want. Remeber that when you save the fin and the pod to number it and rename them. You are customizing. Once you have one fin done you can copy it and paste. After pasting go to that fin and change the radial position and the number. Should take a half hour or so to finish all four fins. By the way looks like a neat desing. Hope this helps. Nukemmcssret
 

nukemmcssret

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I do not know what trouble you are having with the design, but I will guess the fins part. First go to the custom fins. You have to build each fin one at a time. Select custom fins and pick any design, and in plan points design your fin. Go to general and pick one fin in a set. Now you have to position the fin where you want it on your rocket. Next with your fin selected, look at the add new components. You will see pod is the only selection in black. Select it and follow the directions on the screen. You can then select the pod and select a body tube and customize it the way you want. Remeber that when you save the fin and the pod to number it and rename them. You are customizing. Once you have one fin done you can copy it and paste. After pasting go to that fin and change the radial position and the number. Should take a half hour or so to finish all four fins. By the way looks like a neat desing. Hope this helps. Nukemmcssret
No matter where you go there you are.
 

mjennings

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the subassembly tool can help since then you only need to build it once and then put on multiple copies and rotate them to the angle you need.
 

Shade

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Darn I need to spend more time on rockets, cannot believe I just flew my
also 2 year old build for the first time a few day ago...

Well I lost half the rocket on the maiden flight...

It was flown on a single D12-5; I had built it with one of Semroc's EB-60
baffles on deployment I heard an unusually loud pop and the nose cone
baffle, and chute all drifted away very very very far away. The airframe
made a nice tumble recovery and other than a little cleaning will fly again
soon.

I did email Carl at Semroc and they do not recomend EB-60 with 24mm
engines. But he still offered to replace the missing components!!! WOW!!!
Between companies like Semroc and Flis Kits, they make this hobby/sport so
much more enjoyable!!!

So I am scratch building a new tube style baffle and will post some pictures
of it soon.

As far as the flight is was great save for the loss of the NC and recovery
system. Very stable, some slight weather cocking, but less than my son's
Mean Machine.

My next flight will be with a D12-3 but "dummy" engines in the outboard pods
to check for stable flight with the extra mass aft.
 
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Shade

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This is not anything earth shattering but maybe a slight twist on an existing
design or maybe nothing new at all... :rolleyes:

The first picure is of one of Semroc baffles for BT-80 airframes. However,
I did not find any commericially available baffles like this one for BT-60
tubes.

So after giving it some thought and having a friend water jet a few CR's for
me. They are 1/8" lexan and the complete baffle weighs in at 13.4 grams.

I came up with the following. Should have better than double the flow of
the Semroc EB-60 baffle I launched out of the first flight.

101_4292.jpg


101_4290.jpg


101_4291.jpg


BT-60 High Flow Baffle.JPG
 

MarkII

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Hmmm. I installed an EB-16 baffle (nearly identical to your EB-60 baffle) in my Eos and I have flown that several times on Estes E9 motors with no problems at all. How long was your BT-60 airframe, and how far away from the front of the motor did you install the baffle? My motor tube is 10" long (it's 29mm in dia.) and the baffle is installed just above it, so it is 6.25" away from the top of the E9 (used with an adapter).
 

Shade

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Hmmm. I installed an EB-16 baffle (nearly identical to your EB-60 baffle) in my Eos and I have flown that several times on Estes E9 motors with no problems at all. How long was your BT-60 airframe, and how far away from the front of the motor did you install the baffle? My motor tube is 10" long (it's 29mm in dia.) and the baffle is installed just above it, so it is 6.25" away from the top of the E9 (used with an adapter).
The baffle was glued in 8 inches or so from the forward end of the airframe
and I was using 2 lengths of BT-60 tubing. so OAL is 36 inches, lose another
3.5" for the engines (less stickout at the aft end) 24.5". I agree, It should
work, but didn't. I am not the one who scrimps on glue, I am the guy that
has to figure out how to get the drips and runs off.:rolleyes:

BTW, this was my first baffle blow out.

I have another BT-60 based rocket that I had already glued a EB-60 in
I topped the baffle off with some Loctite toughened epoxy and ground
tested it the other night no issues at all.

But the mfr does not recommend the use of these with D and larger so I
will look for alternatives.

My "design" will get ground tested shortly.
 

Eric1

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Very Nice work! I like Guys that think outside of the box!
Keepum coming!!


They qualify! BaDDAzz!
 

renisnceman

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My son and I built something similar with a central I-245 and 3 outboard F-20's. It was based on a "rocket lamp" from American Science and Supply that had 3 outboard pods that we modified to accept 29mm motors. I was able to put it in Rocksim to get some idea of flight stability, and it did well on it's maiden flight, despite a lot of anxiety over those F-20's lighting before the I came up to pressure. We've flown it a couple times since with the same motor configuration.

http://www.youtube.com/watch?v=z-0ppX1JHjQ

Christopher Dale
TRA 12445
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modeltrains

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Interesting! Would have never thought of motors in tube fins.
Rocketeers sure are an imaginative and ingenious lot.
 

Shade

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I have taken a very long break from the sport, life and kids and wife.
I hope to launch tomorrow...
 

BABAR

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Welcome back!
 

Daddyisabar

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You will find many new pod rocket lovers on the forum since your first post. You can even go with a new E 12 in the center for more pop off the pad. Looks like you have it balanced. Use some Q2G2's, a 12v launch system, a long rod in good conditions and you should be fine. It is just an ignition issue!
 

Shade

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She flew today on a single E9-8, ejection right at apogee.
Great flight no damage, ran out of time for a second flight.
 
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