Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
AMW Red Max Build
#11
Bill, I hear what you are saying, but I don't think the honeycomb material had any affect doing just one side. I laid it up sandwiched between two marble tiles with weight applied. The unlaminated fins have the same amount of warp, and FG is rigid enough that I don't see the honeycomb pieces taking the warp out even if I do two sides at a time. It's hard to get a good photo of it to demonstrate the warp. Better to start with a straight piece of FG to begin with I think. I may be being a bit of nitpicker with this. I think some might just slap the fins on and not even notice.
Reply
#12
If they are warped from the begining then they are junk. Contact AMW i would be surprised if they didnt send you a fresh set...


Bill Clune L3 | NAR#88583
Been a launch Director
Founded a Club
MARS Club|SRC|MDRA - Forever
Reply
#13
Minor update.  I took one of the bare fins and put the honeycomb material on both sides. I sandwiched the fin-sandwich between marble floor tiles with weights on top to cure.  The cured fin still had the warp issue.  Warp aside,  I clamped the fin to the workbench to test the stiffness.  The fin is noticeably stiffer than the floppy 1/10 inch bare fiberglass fins, but still exhibits more deflection than I would like.   Overall I think these fins would do a nice job on the stock kit, but I am going to switch gears and make fins from scratch using 1/8" ply, and carbon fiber layers the same as I did in the Punisher 4 build.

   
   
Reply
#14
Mark how big a motor are you going to put in this?? G10 alone might flutter a bit, but it is REALLY TUFF stuff.


Bill Clune L3 | NAR#88583
Been a launch Director
Founded a Club
MARS Club|SRC|MDRA - Forever
Reply
#15
wcluneMark how big a motor are you going to put in this?? G10 alone might flutter a bit, but it is REALLY TUFF stuff.

A 2 grain 75 mm, so a full K or baby L. It will probably reach mach 1 give or take. Yeah, stock fins are probably strong enough for the up part. Landing damage and cracked fillets may be more of a concern with the heavy motor hardware and leverage from the large fins... a 70 inch chute is about the max I can fit.
Reply
#16
you think carbon lamented plywood will be less prone to damaging fillets on landing? They probably wont flutter as much though!


Bill Clune L3 | NAR#88583
Been a launch Director
Founded a Club
MARS Club|SRC|MDRA - Forever
Reply
#17
(02-12-2018, 03:18 PM)wclune Wrote: you think carbon lamented plywood will be less prone to damaging fillets on landing? They probably wont flutter as much though!

No, I was just rambling, because I'm currently making repairs to my carbon laminated Estes Mega Red Max.  The fillets had small cracks on two of the fins after landing at a pretty slow 18 fps.  I'm attributing that to the Proline 4500 fillets getting brittle or just not being that strong.  I couldn't find an easy way to fix it and just decided to remove the tip-tip, remove both fins, and re-attach with new fillets.  I am currently making new fillets with Aeropoxy ES 6209 adhesive which is a little fussy to work with but should be stronger and less brittle.  I had another rocket develop a cracked fillet recently (also  Proline) after doing nothing more than sitting on the shelf for a couple years. I'm assuming it's from shrinkage with age.  Oh well, never using the Proline again.  Anyway, when I get back to the AMW Red Max build, the fin can will be bullet proof with carbon fiber cover fins ( 1/8" ply cores), CF tip-tip and Aeropoxy ES 6209 fillets.

   
   
   
Reply
#18
Well I work in an epoxy manufacturing facility although we don't make adhesives much anymore we do have the ability to test them, which i DID!
Proline 4500 is in my not so humble opinion is the worst thing to use on external fillets in most applications, it is very brittle! External fillets need to be made out of a material that remains flexible, so the unavoidable flutter doesn't damage them.
The best thing for External fillets is actually rocketpoxy or just about anything with some filler in it.


Bill Clune L3 | NAR#88583
Been a launch Director
Founded a Club
MARS Club|SRC|MDRA - Forever
Reply
#19
(02-13-2018, 12:10 PM)wclune Wrote: Well I  work in an epoxy manufacturing facility although we don't make adhesives much anymore we do have the ability to test them, which i DID!
Proline 4500 is in my not so humble opinion is the worst thing to use on external fillets in most applications, it is very brittle! External fillets need to be made out of a material that remains flexible, so the unavoidable flutter doesn't damage them.
The best thing for External fillets is actually rocketpoxy or just about anything with some filler in it.

Agree. I've read Proline is a rebranded 3M epoxy. Wildman or whomever is the source should just let the cat out of the bag and tell us who makes it or what the specs are, before all rockets built using it start falling out of the sky LOL.
Reply
#20
I got the Estes Mega DRM fins epoxied on, and put two layers of CF between the fins, but the layup is only fillet to fillet.  It turn out pretty well... perhaps I'll post a repair build later.

So it is back to work on the AMW model.  To make new fins for the AMW Red Max, I traced the fin pattern from the Estes Mega DRM.  The original AMW fins were a tad different shape from the Estes fins... so I went with the Estes.  I drew the fins in CAD, tweaked the angles and lengths until they matched pretty much exactly.  Here is a .pdf if anybody cares for the full scale fin pattern.  Print it out as actual size otherwise it will likely be scaled to fit, and appear undersized.

.pdf   MDRM Fin pattern 3.PDF (Size: 5.53 KB / Downloads: 1)
 

   
 I sent the .pdf file to laser cutter and cut out some fins. The fins are 1/8" 5 ply Midwest Baltic birch.
   
   

I then cut out some carbon fiber for laminating the fins. The fin layup will be two layers of plain weave with 0/90 orientation with one layer of unidirectional running the diagonal direction (the fins seemed the most flexible in the diagonal direction), for a total of 3 layers per side.  The uni was sitting around left over from another build and I just wanted to put it to use, otherwise I'd have gone with all 3 layers of plain weave.
   
Here's a fin ready to go in the bag.
   
Here is one fin under vacuum... Hoping for good results.
   
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)