"Color The Sky" - 75mm M Powered Crayon Bank

Hello all, and welcome to my thread. This will be my first "build thread" so please bear with me as I try to get a grip on how to post, formatting, etc.

I will also be doing a build log on my website https://sojourner.me, so please check it out!


Crayons have always been central to my rocket experience. My dad's (and by extension mine- although I was about 6 years old at the time)first HPR was a scratch built blue crayon based off of Jamie Clay's Gumby Crayon. We moved on to bigger and better, but we never stopped loving crayons.

Recently I got this crazy dream in my head. HOW COOL would it be to stuff the biggest motor possible in a Crayon?! The crayons are just a little too small to fit a 98mm motor case sadly. We'll have to settle for 75mm.
First off - the plan:



3" Blue tube runs throughout the entire rocket. It's essentially a 3" MD rocket with a crayon bolted to the outside. There are wooden runners bonded to the blue tube that add strength and serve as "centering" strakes. They will be sanded to the shape of the ID of the crayon.



The fincan is reinforced as if the rocket is minimum diameter. this includes large fillets and tip-to-tip. The bottom crayon is then slid over the tube from the front.



Aesthetics: You can make this crayon any colour you like. The first rendition will be pink because real men fly pink rockets! I will be doing 1 or 2 layers of 5.7oz 2/2 till CF over the fins for strength and aesthetics. Carbon just looks really cool juxtapositioned with the cardboard crayon bank.


I'm probably going to stick to baby M's and L's for this rocket- We have so few 75mm rockets anyways it'll be nice to not shred one.

Stay tuned! Soon the building shall begin.

Very cool! So your sliding three of the 4" banks on a motor mount . Great idea picture of the build watching

Interesting.

So if I understand correctly, Your basically sliding a couple crayon banks over a minimum diameter rocket. Very cool! I'll definitely be following. What kind of altitudes do you expect?

At LDRS 12 I launched a 5” Crayon on an AeroTech L952. Was a single crayon, Nike style fins with a 4” Dynacom MMT that went all the way up into the nose cone. The space bettween the tubes was filled solid with epoxy/microballoons, similar to a VERY hard dense foam. NC has a bunch of ballast and foamed.

Motor ejection and a stripped chute. It was repairable but not launched again.

M

I am subscribed to your build thread. What are you going to do for the nosecone? I don't think the plastic one is going to hold up.

Foam may work . Or maybe fiberglass the outside

Foam will hold up, the faster you go higher density foam is required.

What I have done is tie the cord for chute attachment to a washer or plywood disc that is a bit smaller than the flat tip of the nose cone, the part of the cord that will be in the ballast and foam has tape on it so the epoxy/foam will not soak in and make it brittle and drop it in. Mix shot ballast (if required) with epoxy and put it in on the washer, pack it down with a stick and leave to cure. Pull cord tight and add foam, I do multiple pours especially with higher density foams

Mark

I know that the nose will be fine on K's. Here is an ordinary"tripple" crayon we made back in '05 that flew great on K550's. No idea about M's though.

I'll probably fill the excess volume that isn't taken up by the inside 3" coupler with gorilla glue for added rigidity.




I designed the fins in Rocksim to be angular and mean looking. They go well with the stark nature of the crayon nose.

The fins for Color The Sky are made from 1/4" Baltic Birch Aircraft Plywood purchased from Aircraft Spruce. It has 12 plies. This stuff is insanely tough and very smooth.



We started with the template and printed it out. I traced the rough outline onto the plywood and marked where we would need to cut.




After cutting the fins on the tablesaw, we taped lined them up on the root edge and taped them together.



A pass on the belt sander cleans up the edges and makes them all the same.




Next step: beveling the fins.