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The Cheese-It Thread
#1
So a couple years ago I had a crazy desire to see a cheese-it box fly.  Not a little box mind you, but one of those BIG boxes like the ones you get at Costco that hold two bags.  So I started building it but I never finished it.  A couple weeks ago I started rounding up all the unfinished rockets I had laying around and came across it.  I finally finished it... I hope.  Here are some pictures of the finished rocket:
    This is the rocket from the side.  The papered foam fins are on square hardwood dowels.

    This is the bottom of the rocket.  Notice the engine mounts, 2 X 18mm, 1 X 24mm which are meant to be filled with two C6-5|7 and one D12-5.  The engine mounts are glued to the box on the inside and outside.

    This is the interior, the walls of the box are connected to the center tube by 1/4 X 1/16 in balsa sticks and is very rigid. The Kevlar leader is looped around the center tube and is not glued in place.

    This is the layout of the recovery system, and because the rocket is quite heavy, there are two 18 in. parachutes.  Starting at the leader line you will notice the two 1/4 in. by 18 in. shock cords, next to them and connected to the leader line is a 'envelope' to hold and protect the parachutes.  Connected at the other end of the shock cords is the nose cone (HA! Not really..), and two 36 in. Kevlar lines which are connected to the parachutes by a swivel.

I did a couple test swings.  Unfortunately, it is stable ONLY in the plane 90 degrees from the plane of the fins about the center-line.  In building it I made as sure that it would be stable as I could make it, hence the fins on dowels.  But the fins are mounted on the corners and to arrange them so that there would be one on each side would make it look bad, not to mention how much space it take up.  I decided to put the fins on the way they are not thinking that it could have potentially dire consequences later.

My questions are as follows:
Will it fly?
Or will it prove itself unstable and tear itself apart?



(This post was not just to ask for help, I will be posting pictures of the flight(s) when it flys.Smile I have posted this on TRF, but I posted it here first.)
BuiltFromTrash
First RMS Flight: June-17 2015
Pringles Can Rocket
G53-FJ-7 (29-40/120) 92 Newton-Seconds
~1300 Ft
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#2
I think this would fit under "Odd-Rockets" category too!
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#3
You already found the problem...the fins will only help in one plane and it likely will pitch over in the other. If it were me, I would have mounted them so the all pointed outwards from the corners (45 degrees from each face).  Base drag may save you, but I bet not.
Member of MDRA, NAR and NARHAMS;
Level-2 certified but mostly fly G and under;
Volunteer compiler of manufacturer's news for ROCKETS Magazine.
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#4
I think rstaff3 is right. I personally would not attempt to fly it as it is.

I would have done the fins as he said. But at this point, it might be easier to add four more fins onto the same square dowels perpendicular to the existing ones.

Aside from that (Mrs. Lincoln) it looks great to me!
Rich Holmes
Camillus, NY
Secretary / newsletter editor
Syracuse Rocket Club

http://richsrockets.wordpress.com
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#5
(08-13-2015, 11:04 PM)Rich Holmes Wrote: I think rstaff3 is right. I personally would not attempt to fly it as it is.

I would have done the fins as he said. But at this point, it might be easier to add four more fins onto the same square dowels perpendicular to the existing ones.

Aside from that (Mrs. Lincoln) it looks great to me!

I think I will take your suggestion, I reached the same conclusion on TRF.  Well, this build can't get any crazier than this!

(08-13-2015, 10:00 PM)rstaff3 Wrote: You already found the problem...the fins will only help in one plane and it likely will pitch over in the other. If it were me, I would have mounted them so the all pointed outwards from the corners (45 degrees from each face).  Base drag may save you, but I bet not.

I thought about doing this but I decided not to, I thought it would be to hard to get it straight and strong.

Btw, this rocket is entirely assembled with Elmer's white glue! 

Will post pics of final product when finished.
BuiltFromTrash
First RMS Flight: June-17 2015
Pringles Can Rocket
G53-FJ-7 (29-40/120) 92 Newton-Seconds
~1300 Ft
Reply
#6
I think you are right in adding fin are in the other plane. Simple fix for a huge increase in the POS (probability of success, not the other term Smile)

While I would have gone the way I said, adding some fins in the other direction should be trivial. White glue should be fine for weak cardboard (ie packing boxes/tubes) and wood. Straight should be trivial given square edges on the body and straight pieces of wood. As long as all the fins are straight (not canted) you should be fine. If they are slightly asymmetric it won't matter much. I have built many a rocket with intentional asymmetry. As long as there is enough fin area in both planes, you should be good.
Member of MDRA, NAR and NARHAMS;
Level-2 certified but mostly fly G and under;
Volunteer compiler of manufacturer's news for ROCKETS Magazine.
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#7
The fin mounts might be a little canted, but I'll be sure that the new additions are as straight as possible.
BuiltFromTrash
First RMS Flight: June-17 2015
Pringles Can Rocket
G53-FJ-7 (29-40/120) 92 Newton-Seconds
~1300 Ft
Reply
#8
Decided to cut the fins off and re-glue them on at a 45 degree angle. Will update when I can.
BuiltFromTrash
First RMS Flight: June-17 2015
Pringles Can Rocket
G53-FJ-7 (29-40/120) 92 Newton-Seconds
~1300 Ft
Reply
#9
As was mentioned earlier:
I would be best if the fins protruded from the corners at some angle. 45 degrees if the box is square, less angle (toward the shorter sides) if the box is rectangular.
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