Kestrel Ex

[Anonymous]

I got the fins attached and glassed. I made a video of the process I use.

http://www.youtube.com/watch?v=7Aqj3xcCWjU

Tony

[Warren B. MusselmanModerator]

Nice video Tony. Now if you only vacuum-bagged, you could get 6oz fabric to lay down that tight and have a much stronger layup.

Edit:
– I’m curious about the epoxy too – what brand? Post-cure?

[John A. WilkeParticipant]

Thanks for sharing that, Tony – I always learn something when I look over your shoulder. Some questions:

– is your “wet cat hairball” fillet the only fillet you apply? earlier on it looked like you had a small fillet, and the carbon-laced one looked like the 2nd set of fillets (but I couldn’t tell for sure)

– what is that brand of epoxy again? I couldn’t make it out in the video and I didn’t recognize the name on the bottle

– how much sanding do you do? And I’m assuming you do wet sanding?

For my part, I tend to use more glass – but I know I also sand a tremendous amount of it away. I also forego paint, so I must save a few microns there 8)

Tony, it is awesome you are sharing all this with us, when are you going to fly it? and are you going to go with your Swamp Gas formulation when you do?

[Bret PackardParticipant]

Thanks for posting that! I watched it a couple of times last night. Always cool to see how other people do it. I’ll probably start on my KestreL next so that was a welcome bit of motivation.

[Dave Smith]

What a great video!
question: when do you remove the tape?

you also mentioned that thinning epoxy was “controversial”. What are some of the pros and cons to that?

[Warren B. MusselmanModerator]

If you chemically thin pretty much any epoxy more than 10%, you significantly reduce the cross-linking in the polymer during cure and thereby reduce the strength of the epoxy. Some manufacturers will even tell you that it reduces strength more than 75%! If I need my epoxy thinner, I warm up the two parts SEPARATELY before mixing in a hot water bath. Be careful with this as it will accelerate the cure rate and shorten pot life.

[Doug GerrardParticipant]

I use the PRO-SET epoxies because in addition to different hardeners, they also offer resins of different thicknesses. I prefer their 125 Resin Low Viscosity for everything and always add fillers to thicken it up to desired consistency. By using different hardeners dictates my working and set up time.

Doug

[Anonymous]

Warren. My modifications are meant for the average builder. The epoxy I use is called Raka. Greg Fannin turned me on to it years ago. In 2004 Greg went 33K at mach 2.4 with this epoxy. His fins held up fine. The paint did not.

John, Yes that cat hair ball is the only filet that I use. It is kind of hard to contain all those little carbon fiber hairs. The filets are smaller then they look in the video. A little hair ball smearing does take place..making things look bigger then they are.

Raka 900 epoxy and 631 hardner I’m not sure there are any specs on it. I just know I’ve had good luck with it It’s a 5 – 1 ratio
[/url]http://www.raka.com/

The fins took me about an hour of wet sanding with 150 gritt.

I’m not going with pain on this one either.

The first 3 flights will be in May. On 3 EX motors in the AT 54/2560 case. One will be Swamp Gas the other two modifications to Swamp Gas.

Spacecoastkid, The tape gets removed when the epoxy if green..rubbery. I run the glass on the big side and use the tape as a line to cut the glass down to. I keeps from needing to do a bunch of extra sanding.

As Warren pointed out…it’s not all that good for the integrity of the epoxy. I’ve seen charts that tell how much strength you loose according to the % thinned and what you use to thin with. Again This has all been working for me. I don’t have fins raining down on me and I feel I push my rockets pretty hard. Until I have issues I’ll keep doing it this way.
After reading Warren post I wonder what % I am thinning it. I’ll go play with some in the shop tonight.

I just want guys to know that there is nothing wrong with this kit designed or how the instructions say to build it. I’m just looking at ways to squeeze more altitude out of it with some modifications that the average guy can do at home.

Tony

[Bruce R. Schaefer]

John, was that you calling him? 😉 That is one of the best instructional videos I’ve ever seen. Traditionally, the elliptical fin is the most drag “free” fin, and the clipped delta just 1 % below that, the thing I really love about this hobby is that we all try different things. That was really impressive and eye-opening. So nicely done! Bret, this was really great for you, dude… as well as the rest of us! Tony does what Warren does, unlike me going full-bore on multi-layers, Tony feathers it out. Hmmm…

[John A. WilkeParticipant]

Warren. My modifications are meant for the average builder…….. Again This has all been working for me. I don’t have fins raining down on me and I feel I push my rockets pretty hard. Until I have issues I’ll keep doing it this way. Tony

We can all learn from Tony. It is no exaggeration to say that he has gone higher than any 3 of us put together (I’m serious) and if it is good enough for T… it is good enough for me!

Those fins on Greg’s rocket look vaguely familiar! Greg is another exceptional flyer.

Thanks for the insight, Tony – I can’t wait to see what you get for altitude. I just hope it doesn’t burn up during re-entry 8)

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