Hey guys,

I got the fins on my Kestral sanded down, and thought I'd share another picture. Still need to polish for the final WOW factor.

Pretty D@m Nice!

I'd have to say that looks like a gorgeous job. Makes you wish you had some hand-laid carbon fiber tube instead of PF green tubing...

Nice pictures and a damn nice job. Hope I'm there to see it fly.

Whistles! Come from the crowd, as the newbie presents his biGGest rush yet. I spent 4 hours today teaching my self how to pack the chute in the upper section, 36" Fruity, No Z-fold here, Quad fold is your man.
I read all the other post on Vent holes, but no one really address Vent hole and sear pins, Do both? Nah, i just use sear? Never fly without a Vent hole? Thoughts?
Bird should reach speeds of 1600+MPH. Using 3, 2/56 nylon screws. I used 2 of the same on Little Blue Dawg, just reaching 803MPH.
So if use a Vent hole, place close to the charge? place away from the charge? place just in front of the piston?
At 25K could I really have a pressure difference of 18 PSI?
All just pft.. minor details. Here is a couple of pictures.

Thats a nice Little Dawg on the left........but he doesnt look blue! 😉
The thing in the middle looks pretty good too. 😉

Are those rail buttons I see? 😯
How do you mount those, being a minimum dia. 😕
Nobody has introduce Mr Wolves to the tower? 😕
Just like hangen a couple of Barn Doors out in the Wind. 😉

Shear pins + a vent hole.

On my L3 I had an issue of the main decided to leave at drogue deployment so I had to ground test quite a bit. I ended up with 6-32 shear pins and a 1/16" vent hole. I would at least upsize to 4-40 and 3 shear pins.

Edward

At 25K could I really have a pressure difference of 18 PSI?

Ya know, I never thought about it, but if that was in there at apogee, might help get the laundry out. At least the nose cone off. 😉

18 PSI? STP is ~14.7 PSI. To have a difference of 18 PSI you'd have to either be sucking quite a bit or blowing really hard.

Edward

Sarcasm aside:

Atmospheric Pressure at 5,000' is ~12.2 PSI, at 30,000' it is ~4.4 PSI. That is a 7.8 PSI difference. Multiply that by the surface area of a 54mm bulkhead (~2.15" Diameter), 3.64 IN^2 and you get ~28.5 pounds of force.

For my KestreL I used 4 ea. 1/16" polystyrene shear pins and I had a 1/16" vent hole up top.

I used a smaller chute (30" IIRC?) and I have flown things thattaway 6-8 times...

Your actual mileage may vary.

Hey,
Yeah, 3 rail buttons, but there little ones, and besides barn door open usually keeps my rocket cool, so why should this one be any different. I ended up going with a vent towards the top, figured by that time, the piston had everything already out. Rail buttons could be used for a guitar strap for portage, he he. Still need to ground test, going to start with same thing I used for Little blue dawg, .3 gm for booster and .6 gm. for nosecone. Anyone else use a much different amount of powder?

On a slightly bigger rocket (volume wise) I used 1 gram for the drogue and then 2 grams for the main.

Edward

My KestreL (which is, of course, the same size as yours) had 1.125g of 4F for the drogue and 0.6g for the main. No piston on the drogue, but I did have a piston up top.

The lower was contained with surgical tubing.

Edward - I think your reference was for a 2.5" diameter rocket, correct? That makes more difference than you might expect vs. the 2.125" diameter (r^2*pi) I think you also had a bunch more vertical space. Bottom line, there isn't much room in the KestreL.

Always - always, always ground test. Add a bit more bp and reef the shock cords and you will be just fine...