Mega Rebel with Monokote

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Crawf56

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Sorry for being vague, trying to work quickly on my phone.

I was just musing about how the CP of the open-framed rocket is a bit of a mystery (to me at least), which makes me wonder whether the skinned rocket will be more or less stable.

It might be totally fine, I just realized that the answer isn’t necessarily obvious (again, to me). However, the skinned rocket would be easy to model in OR or Rocksim to find CP if desired. The unskinned rocket... who knows.
I confess, that I tend to build kits, not design new rockets. So I do not spend much time on Center of Pressure vs Center of Gravity relationships. However, I do normally conduct the old 'string test' (attaching a string to the rocket at the CG, w/ motor installed, and swinging it around).

When initially building the Mega Rebel, I was surprised that no CG was listed. When I contacted the Rockitarium (kit seller/designer), they stated that the Mega Rebel had been an act of trial and error. This was why I was careful to add CG info (that I obtained) during my Mega Rebel build.

So, living in the middle of nowhere in northeast Arkansas can have its advantages.
 

BABAR

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So, living in the middle of nowhere in northeast Arkansas can have its advantages.
If a tree launches a rocket in the woods and the rocket does a St.Louis Arch and then a long landshark, but nobody else sees it, it didn’t really happen!
 

Crawf56

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It looks like the kit's vertical 'spars' stick out a little bit beyond the outer diameter edge of the horizontal rings (maybe 1/16" +/-) and this makes it hard to cover the openings with a 'smooth' panel surface?
Sorry I am replying so late to your comment, Space Ranger. Yes, you are correct. I had considered sanding the vertical 'spars', but decided it wasn't worth the effort. In hind sight, it might have been worth the effort.
 

Crawf56

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MONOKOTE TECHNICAL ALERT! :headspinning:

The Mega Rebel is made of PLYWOOD, not balsa. Monokote does not attach to plywood as well as balsa, so I had to increase the temperature.

I initially stated that I was doing an initial 'attach' of 250 F. This turned out to be more like 275 F, or higher. When attaching monokote over monokote, it was closer to 300 F.

Still did final stick/shrink at 325 F. When using heat gun, used 'HIGH' setting.
 

Crawf56

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If a tree launches a rocket in the woods and the rocket does a St.Louis Arch and then a long landshark, but nobody else sees it, it didn’t really happen!
Exactly. :dancingelephant:

I tend to go to Memphis launches (1-1/2 hour drive). Once the Covid stuff calms down, I hope to get up to some St. Louis launches (3-1/2 hour drive).
 

aerostadt

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I tend to think that the standard rocket simulation computer codes do not have any real meaning for the flow pattern around the Mega Rebel. So, if they did give a CP location how much would valid would it be. The original Mega Rebel flies, therefore it must be alright. The original question is how does the CP location change. We don't have calculations showing how it changes, but I tend to think it will be OK. The proof is in the flying or Daddy might say use "mindsim".
 

Crawf56

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Onward to covering the fins. I debated doing this, since I am adding weight aft of the CG. But plastic covering is pretty light, and it looks good.

Decided to use red.

m_IMG_1261small.jpg
 

Crawf56

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Here is how it looks on the other side of the fin. Did the "cut & fold" method.

m_IMG_1263small.jpg
 

Crawf56

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And a look on the back side. A lot of better monokote guys would stretch it over. Just doing what works for me.

m_IMG_1265small.jpg
 

Crawf56

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Every once in a while, there is a color that the bugs like. Had a Fokker Dr.1 triplane with a yellow top wing and elevator; some little gnat just loved it, there would be 10+ when it sat for a little while at the RC airfield.

A little jumping spider seems to like the orange monokote. It patiently sat while I covered two more fins. I did release outside, on a bush.

m_IMG_1271small.jpg
 

Crawf56

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Here we go. I like the red fins with the orange and metallic purple. Still one more fin to cover.

m_IMG_1272small.jpg
 

Crawf56

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Tested with the Aerotech E15-4W. A E-size motor designed to fit in a D motor mount.

m_IMG_1278small.jpg


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