Has anyone used honeycomb nomex for a fin material? Was wondering if it would hold up to mach + flight and if there was a problem with flutter. If it works it would seem to be a very lightweight solution.
Steve
Steve
Honeycomb Nomex
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dixontj93060
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In general Nomex or Aramid fabric is not as stiff as carbon fiber. Saying that I have done no simulation analysis of the material in a honeycomb configuration. Your supplier/manufacturer should be able to give you the physical properties of the material then you could simulate to get flutter results.
I was thinking of edging the fin with wood or fiberglass, filling the inside of the fin with nomex honeycomb and then covering the fin with carbon fiber. Should make a lightweight fin just not sure how stiff or strong it would be.
ECayemberg
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Two similar examples; the fin structures of both worked well: G to M powered.
This was Gatorfoam core with carbon skins and balsa leading edges:
And this one was plain nomex honeycomb...no leading or trailing edge caps, just cut out the shape and epoxy them in place.
Flying trees and pumpkins are the best!
-Eric-
This was Gatorfoam core with carbon skins and balsa leading edges:
And this one was plain nomex honeycomb...no leading or trailing edge caps, just cut out the shape and epoxy them in place.
Flying trees and pumpkins are the best!
-Eric-
Two similar examples; the fin structures of both worked well: G to M powered.
This was Gatorfoam core with carbon skins and balsa leading edges:
And this one was plain nomex honeycomb...no leading or trailing edge caps, just cut out the shape and epoxy them in place.
Flying trees and pumpkins are the best!
-Eric-
I highly advise against edging with balsa. I did just that with some honeycomb I got from Giant Leap years ago. When the rocket got dragged through the playa the balsa caused the tip to tip to split and the edges of the fins got ripped up real bad. Use a hardwood dowel or G10 strips.
RocketFeller
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Another option is end-grain balsa core material - I love the stuff!
rharshberger
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+1 end grain balsa panels
CzTeacherMan
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Two similar examples; the fin structures of both worked well: G to M powered.
This was Gatorfoam core with carbon skins and balsa leading edges:
And this one was plain nomex honeycomb...no leading or trailing edge caps, just cut out the shape and epoxy them in place.
Flying trees and pumpkins are the best!
-Eric-
What?!?!.... I expect to see a flying tree at MWP. No excuses. I'm not flying anything (except the drag race), so I'll help...
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No no no... We want Pyro Pumpkin v 2.0... :horse: :horse: :horse: :horse: :horse: :grin:
Will end grain balsa with carbon fibre hold up to mach 2+ speeds? Is it that stiff? How many layers of carbon do you use?
RocketFeller
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I ended up going with end-grain balsa after consulting with a tech from Fiberlay, a local composites company. In his opinion balsa was the best core material in terms of strength and thermal stability, at a slight weight penalty over Rohacell (spelling?) foam or Nomex honeycomb.
For our application we needed very stiff fins to resist flutter. Our rocket was very much a "low and slow" type, but with an 11" chord and a 27" semi-span, they needed to be strong. We used 1.3mm plate to skin the balsa, which is, in retrospect, overkill. We made some very stiff internal reinforcement pieces from .5" end-grain balsa covered with a single layer of six ounce CF cloth. I would think that three layers would be practically bulletproof.
For our application we needed very stiff fins to resist flutter. Our rocket was very much a "low and slow" type, but with an 11" chord and a 27" semi-span, they needed to be strong. We used 1.3mm plate to skin the balsa, which is, in retrospect, overkill. We made some very stiff internal reinforcement pieces from .5" end-grain balsa covered with a single layer of six ounce CF cloth. I would think that three layers would be practically bulletproof.
dford
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You saved considerably on money also. Cutting honeycomb can result in lots of waste product because of ribbon direction. It also likes to have perfed film adhesive for a full bond to each cell structure, assuming you'd cure your fin in an oven under vacuum. Costing more but without it the core isn't to its full potential.
I'd like to see how your balsa core turns out.
I'd like to see how your balsa core turns out.
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rharshberger
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Mine turned out like this, the weight savings was pretty minimal, however the fins were very strong and stiff with only 2 layers CF each side. The rocket really didn't push them all that hard on a AT M1297W. The cost savings and ease of layup was some of the reason I used the end grain balsa sheet (which is a 1/4" thick). Dan's upscale Dragonfly turned out really well, I too am interested to see it on a more powerful motor.
dford
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Is the core sort of a window cut out with end grain in the window?
Your carbon looks cured under vacuum?
It looks good and sturdy. Certainly tosses a few new ideas into my mind as well...
rharshberger
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Exactly, the fins were cut from solid 1/4" Baltic Birch plywood, then they were used as a pattern to cut the "window panes", the fins were then vacuum bagged with a Foodsaver. The fins are pretty stiff. The whole process is detailed in my L3 build thread which I can link when I get to a real computer.
https://www.rocketryforum.com/showt...t-Cherokee-D-L3-build-thread-for-rharshberger
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dford
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Rich,
Your vacuum setup is genius for in home composite work.
We cut with "re use able" blades, the kind that a piece snaps off when dulled and gives a fresh tip. Those old tips are often found after a cure under vacuum in the lay up. Along with silver pencil lead, gloves, straight edges. Hell even a piece of paper has shown up after vacuum. LoL.
A good way to know, if you are interested in knowing, for any core, layup the underside first, then do the breather thing and perf film (if used). Keep the layup on the bottom side and once under vacuum you should see on the top where the problem high-low spots are in the breather, feel with your hand. If none are noticeable, once done curing just feel with your hand along the flat top exposed portion after it has been vacuumed. Fill/sand as necessary, then layup the top and re-vacuum. I'd even resin wipe the carbon after to fill in the fabric entirely for a smooth glass like finish.
That's how I do it for real aerospace grade parts, pre pregnated or wet lay up. Unless the part is being bonded to something else, then I'd skip the resin wipe on that portion.
Edit: the vacuum process I described is only if you vacuum to a flat surface. The sandwich bag method won't work to find high and low spots.
Your vacuum setup is genius for in home composite work.
We cut with "re use able" blades, the kind that a piece snaps off when dulled and gives a fresh tip. Those old tips are often found after a cure under vacuum in the lay up. Along with silver pencil lead, gloves, straight edges. Hell even a piece of paper has shown up after vacuum. LoL.
A good way to know, if you are interested in knowing, for any core, layup the underside first, then do the breather thing and perf film (if used). Keep the layup on the bottom side and once under vacuum you should see on the top where the problem high-low spots are in the breather, feel with your hand. If none are noticeable, once done curing just feel with your hand along the flat top exposed portion after it has been vacuumed. Fill/sand as necessary, then layup the top and re-vacuum. I'd even resin wipe the carbon after to fill in the fabric entirely for a smooth glass like finish.
That's how I do it for real aerospace grade parts, pre pregnated or wet lay up. Unless the part is being bonded to something else, then I'd skip the resin wipe on that portion.
Edit: the vacuum process I described is only if you vacuum to a flat surface. The sandwich bag method won't work to find high and low spots.
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