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Building a Crayon

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Hospital_Rocket

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So it seems to me that people feel that building a Crayon is fun.

Hokay, I'll give it a try

Step one - Buy a Crayon Bank

Now what?

I know, I kmow Add fins, MMT, yada, yada...

Dumb question (make that plural) time.

1) how far back from the end of the "wax" do you end the nose cone?

2) I want to fly this thing on a 3 x 24 cluster. Should I use TTW fin mounting.

3) Colored fins or clear?

4) How do you patch the hole where the coins go in?

5) Is there any issues with the plastic body and the heat of the deployment charge. I was thinking of building the flying components within a stuffer tube to isolate things.
 

jetra2

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Originally posted by Hospital_Rocket

Now what?

I know, I kmow Add fins, MMT, yada, yada...

Dumb question (make that plural) time.

1) how far back from the end of the "wax" do you end the nose cone?

Beats me, truthfully....:confused:

2) I want to fly this thing on a 3 x 24 cluster. Should I use TTW fin mounting.

Umm...I would say that it wouldn't be necessary, but for added strength, you could dado-slot the tube by not cutting a full slot, but only about 1/2 the way through the tube. This way, you won't have to make a tab for the fins, but you get a good amount of added strength by allowing the epoxy to soak in better.

3) Colored fins or clear?

That's really a personal preference, but I think the clear fins look cool. It really makes it have the 'Flying Crayon' effect.

4) How do you patch the hole where the coins go in?

Maybe a small sliver of the plastic from the side of the nosecon in an inconspicuous spot?

5) Is there any issues with the plastic body and the heat of the deployment charge. I was thinking of building the flying components within a stuffer tube to isolate things.

I thought about this for a minute, and then came upon the same solution that I'm going to be using on my Estes Saturn V. I'll be running a BT-70 up the middle of the body for use as MMT and stuffer tube. Simply cut some rings with a 2.2" hole in the center, use a Fliskits EMK3-24-70 Engine Mount Kit that you can get for under $5, and run the BT-70 all the way up the tube to the nosecone where you'd have some sort of shoulder, likely made out of a BT-70 coupler, and attach the NC to that. This might work for ya.
Jason
 

Hospital_Rocket

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As I think about it, I might leave the coin slot in and sit the the rocket next to my tent.

Put a sign over it

"Help sponsor a stable flight - Insert nose weight here.."
 

rstaff3

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Hehehe, that would be a riot! :) I can't answer all your questions as the only crayons I've seen/used have plastic 'wax' (ie the nose and tail sections) but have a nice sturdy cardboard body. A stuffer tube might be best if the body is plastic. As for the coin slot, I filled mine with hot melt glue.
 

Bowhunter

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I use TTW fins on all my crayons it just a little insurance that you know its built strong and as far as the cluster OH OH OH OH on a 3inch it all depends on the weight of it but id go 4 or 5 24mm. Just my 2 cents
 

cls

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my take on it

1) not sure what you mean ?? trim the ridges on the shoulder of the nose cone to make it slide easily. use gorilla glue to put a 1/8" x 3.75" plywood bulkhead inside the bottom lip of the nose cone. put a screw eye in the plywood.

2) TTW definitely. 3x 24mm ought to be good. you need at least F40 power, so 3x E15s or more.

3) colored fins! painted plywood. get creative with the shape.

4) put a piece of masking tape on it if it bothers you. leave it open and listen for the whistle.

5) plastic body ??? did you buy a Ralphco crayon bank, or another kind? can you post a picture?
 

Hospital_Rocket

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The body all the way from top to bottom is a single piece of plastic. I was wondering how far back from the yip people customarily make the BC/BT transition. I've chosen the point where the "paper wrapper" begins.

I'm reconsidering my propulsion. I may go to 1 x 29mm and 2 x 24mm.
 

rstaff3

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For my next crayon, I'm going to try Bob Kaplow's fin mounting method that he published in Sport Rocketry (possibly a small variation). He pop-riveted aluminum angle stock onto the airframe with aluminum bar backing. The clear Lexan fins are then bolted onto the angle with cap screws so they are removable. Ov course the cost for the hardware is more than the crayon bank, so hmmmm....

Well, if I had read this thread closer I would have seen brianc gave a link to the Kaplow design...ooops
 

phaar

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I would leave the hole open. At first I was opposed to it when we made our first one but one crayon we have came in balistic because of a too long delay. It was luckily saved by some trees but it fell like a rocket. It was pretty cool because it whistled on the way down, sort of the same as a bomb falling from the sky. Then, BAM! We recovered it with a fin still intact, which was pretty surprising. We used lexan for our fins. It makes it look really cool, especially at those dusk or night launches. There is just a crayon with fire comin out the back flying through the air. Pretty impressive, I think. For the end of the nose cone, I cut out a circle out of birch that was about 3.5 inches (I think) and shoved it up as far as I could making a bulkhead and the nose cone stronger. Then we slapped a hook in and tied the shock cord. There was probably about 3 or 4 inches from the back of the nose cone to the bulkhead. It pretty nice. I will post pics if I can get some.
 

rbeckey

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I used masking tape to cover the outside of the slot, attempting to preserve the curvature of the surrounding material. I also roughed up the inside of the cone in that area and the base and point with 60 grit sandpaper. I then took a mixture of 30 minute epoxy and microballons and put it into the slot from the inside, making sure it got spread around onto the roughened interior surface, and placed an epoxy soaked scrap of nylon hosiery into the wet mixture to help keep it together. WHen it set, I pulled the tape and sanded the whole thing lightly, then painted with Krylon Fusion. I used polyurethane glue for the bulkhead and to secure the nose weight. The roughened plastic will help give it some grip.I cut slots in the tail with a Dremel and mounted lexan fins through the wall to the motor mount, since very little bonds to the plastic in those banks. I masked the clear fins, sanded and painted the tailcone with Fusion. The paper sleeve on the body I sprayed with clear satin. It really looks more crayonish that way, with shiney smooth "wax" and a matte finished "wrapper."
 

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