My Large 3D Paper Fins

[McKailas Dad]

This is an early prototype I made with posterboard.

I am working in 'Paint' to reverse-engineer a pattern.

Eric (SpaceAXEplorer) has been kind enough to help me tweak its final design.

These fins will be going on my 5.25 Tube

and at the other end of my PBNC

Sooooo...... ?

[chadrog]

I've been wondering if you've been working on this, fins look great.

[Pem Tech]

Thanks for the PM I had missed this.
Very nice.....

And by the way, your PM box is full.....

[Rocketbuilder]

Very cool! That is going to be one ginormous rocket!
Is the pattern something you'd be willing to share with us?

[[POW]Eagle159]

an all paper rocket!?!

Looks nice, I bet they are nice and light too.

[jflis]

Yep, this is very cool! I am going to have to try this design and check this out

[McKailas Dad]

Thanks Jim! I must admit, your Midnight Express fin design is what gave me this idea.

Although I couldn't just upscale your design, that wouldn't be very original.

I went through a few designs, until I came up with the shape that looked good on the tube.

With the fins being all paper, I didn't want a fin that went below the body tube, I didn't think they would last more than a couple flights.

As it is, I think I will be setting this up as a rear eject, my PBNC (Poster Board Nose Cone) is quite sturdy!


I will keep you updated on my progress....



PS How in the heck am I going to Sim this?

[McKailas Dad]

While this fin is pretty sturdy, any ideas on how to make it more rigid, internally?

One thought would be to use a few pieces of tube (~BT50?), and compound-cutting it to fit laterally.

Another idea would be to have internal folded sections nestled into each other at about 2/3's and 1/3 the height? 3 layers total... Like a fin, in a fin, in a fin.


Any ideas would be great, I've never made a paper fin this big before...

Thanks!

[Rocketbuilder]

I'm not exactly an expert, but I would suggest making paper I-beams of some sort and glueing them inside the fin.

[powderburner]

While this fin is pretty sturdy, any ideas on how to make it more rigid, internally?

I think you are already headed in the right direction, and Rocketbuilder has also given a good idea.

I would point out that the most simple math/shape/fabrication would be to cut some spars that run directly under those surface fold lines. This gives you straight sides to your spars and also supports the fin surfaces a little better (they are going to tend to "crease" anyway, from fingers/handling abuse, on top of whatever internal reinforcements you add). Spar materials could be CA-soaked cardboard all the way up to parts cut from fiberglass sheet.

And don't forget a good solid root rib to support the fin shape, and to add more bonding surface for gluing the fin to the local body.

[plastic_gorilla]

i looked at all of that and thought... great stuff... could you take one perfect one, make a mold and then turn out masses of great stuff foam or 2 part urethane foam fins? perhaps it violates the paper rocket code....

/just gave me some interesting ideas though...

[McKailas Dad]

...make a mold and then turn out masses of great stuff...

Hmm, I think you may be on to me, sort of...

I am thinkin', since I have to make 4 of these, that I would make a 'fold-mold'

Material yet undecided, (Plexiglass, thin plywood or ?) to use as a pattern for the folding.

Hard to describe, but like papering a fin, but then removing the fin. A buck or a mandrel, not sure of the correct term.

If I made the pattern or patterns correctly, I could make them consistent, repeatable, and may not even have to measure anything.

Then, I could 'turn out masses of great stuff' (yea, I know you were talking about foam, I'm just being punny)


Lay down paper--> then pattern on top--> fold over--> cut--> remove pattern.

Yea, it's 2:45 am, and it makes perfect sense to me.


Maybe I can come up with a better explanation after some Zzzz...



Definatly some good ideas on how to make it more rigid, keep em coming!

I'm liking the rib idea, seems the least difficult, though I never thought it would be easy!


Thanks again.

[chadrog]

I think a cardboard core would do the trick, it would be easy to sand to keep your bevels how you want them as well.

[[POW]Eagle159]

I have made fins out of cardboard before....

I cut the fins out, and Then I cut a small strip of paper out and glued that to the edge of the cardboard to cover up the inside... Does that make sense?

[aditat2]

Actually that makes perfect sense. It gave me another idea as well - cut the fins out of corrugated cardboard then glue a sucker stick to the top edge and you have an airfoil type leading edge.