L3 Certification Build: 8" Upscale Frenzy

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I'm planning to do the cert flight some time at Higgs this fall-winter season. It will depend on when I finish all the painting, wetsanding and polishing. I don't normally paint during the summer because I paint in the garage and it is usually too humid in the summer. So we'll see how it goes. If I get enough low humidity days I may be able to paint it this summer, otherwise it may not get done until cooler weather. And after the actual spraying of paint I will then have a whole lot of sanding and polishing to do which is going to take a long time.

In any case I'll probably do a shake down flight first on a L motor down here at Battlepark in Culpeper before I bring it up to MDRA for the L3 cert flight.
 
Hey John, I heard you had a little mishap at the sod farm on Saturday. What went wrong?
 
Hey John, I heard you had a little mishap at the sod farm on Saturday. What went wrong?

I had two CTI I223 Skids from the same batch. Launched one last month and it was great, so I didn't bother to check the forward closure on the second one. Woops. My MAC Scorpion turned into a fireball. Fortunately, it ignited the BP charge and separated at the coupler, and only the booster was damaged. Rebuild coming.
 
Here is my main chute deployment test with 7.5 g powder. I think this is probably a little too much. That harness is 35 ft long. I would like to have just enough energy that the nose cone hits the ground before reaching the end of the harness. I'll try again . . .

[video=youtube;p_meQ6Zu2KY]https://www.youtube.com/watch?v=p_meQ6Zu2KY[/video]
 
7.5 grams might be a bit much, but you know that sucker is coming out! Maybe use 7.5 as the back-up instead of the primary?

After deployment, I see your Nomex is right next to the chute itself. I would suggest attaching the nomex to the recovery cord about 10-15 feet below the parachute attachment point. This will reduce chance of tangling in the air.
 
My F200 uses 6.0 in the main, with a backup of 6.5. Booster uses 5.0 with a 5.5 backup. Looked way over-enerjetic to me. You don't want to stress the cord.
 
Here is my main chute deployment test with 7.5 g powder. I think this is probably a little too much. That harness is 35 ft long. I would like to have just enough energy that the nose cone hits the ground before reaching the end of the harness. I'll try again . . .

[video=youtube;p_meQ6Zu2KY]https://www.youtube.com/watch?v=p_meQ6Zu2KY[/video]

lol if I was your neighbour I would be running for cover. I thought it was going to hit or go over the fence.
 
My F200 uses 6.0 in the main, with a backup of 6.5. Booster uses 5.0 with a 5.5 backup. Looked way over-enerjetic to me. You don't want to stress the cord.

Yeah I agree, my next test will be 6.5g. My payload tube is a bit longer than your F200 so I'm hoping that will be about right. If not, I'll keep testing til I get it.

lol if I was your neighbour I would be running for cover. I thought it was going to hit or go over the fence.

Ha, that's my house on the other side of the fence. I have a 5 acre wooded lot so no neighbors nearby to worry about. And I'm up on a bluff overlooking the Rappahannock River so there is nobody back there except a lot of wildlife. I probably scared some deer.
 
Here is my main chute deployment test with 7.5 g powder. I think this is probably a little too much. That harness is 35 ft long. I would like to have just enough energy that the nose cone hits the ground before reaching the end of the harness. I'll try again . . .


Correct..
You should try for about 75% on the length of the harness...
Don't forget,,
As the rocket sits at a 45 angle leaning against the chair there is tension on the coupler that won't be there during flight..
In flight when that charge goes off that joint will be weightless...
So the charge will be a bit more effective / efficient...

Teddy
 
Also that baffle in the payload tube works perfectly. Usually I get black soot and even blast holes in my chute protectors because normally the chute is sitting right on top of the charge canisters. But with the baffle holding the chute near the top of the payload tube, the chute protector came out clean. And there is no damage to the baffle, at least not after two ejection tests. As you can see from this shot, it takes a serious blast. The ejection gas shooting out the side of the tube in this image is from the tiny vent hole.

34830047883_fb7497e8a6_o.jpg
 
I also noticed in that image that you can see some ejection smoke coming from the av-bay vent holes on the switch band. I assume that this is because I have not yet sealed the holes in the av-bay lids that the wires pass through. Good thing there are no altimeters in there yet.
 
Great picture Nathan, really neat to see what happens at the moment the charge is firing.
 
This is requiring a lot less powder that I expected. The 6.5 gram test looked about the same as the 7.5 gram test. So I tested again with 5.5 grams. Looks like still a little more powder than is necessary but I'm going to go with 5.5 grams for the main.

This is really strange because I use 5 grams for main deployment in my Formula 150, and the payload section on this rocket is about twice the volume of the payload section of my Formula 150.

This is the 5.5 gram test:

[video=youtube;SQXeeWY2yOI]https://www.youtube.com/watch?v=SQXeeWY2yOI[/video]

Now on to the apogee deployment test . . .
 
Here is the apogee deployment test with 4 grams of powder:

[video=youtube;-Pj0i3anUrk]https://www.youtube.com/watch?v=-Pj0i3anUrk[/video]
 
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How will it fall under drogue? When the main charge goes off will the forward and aft body tubes damage each other?


Steve Shannon


Good question, since that has happened to me before. The harness is 35 ft and the drogue is attached to a loop 6 feet from the end that is attached to the payload section. So while it is descending under drogue the booster section should be hanging below the payload section.

A couple of years ago I saw a L3 flight in which the main deployed while the nose was pointing straight down. The payload section fell into the chute and got tangled. I don't know if there is any way to prevent that from occurring, since the payload section always tumbles a little during descent even with a drogue and you can't control the attitude that it will be at at the moment of deployment.
 
Good question, since that has happened to me before. The harness is 35 ft and the drogue is attached to a loop 6 feet from the end that is attached to the payload section. So while it is descending under drogue the booster section should be hanging below the payload section.

A couple of years ago I saw a L3 flight in which the main deployed while the nose was pointing straight down. The payload section fell into the chute and got tangled. I don't know if there is any way to prevent that from occurring, since the payload section always tumbles a little during descent even with a drogue and you can't control the attitude that it will be at at the moment of deployment.

The heavier the nosecone and bigger the drogue the more likely the nosecone is to hang straight down. Lighter weight forward sections with small drogues tend to drift down. The sections could still strike, depending on the direction they're pointing when the charge goes off.


Steve Shannon
 
Great picture Nathan, really neat to see what happens at the moment the charge is firing.

Heck yeah,,
What a cool pic Nathan..

Check this flight of my rocket "SteamPunk"..
It's 4" all glass X 9 1/2 Ft..

https://onebadhawk.com/uploads/3/4/7/5/34752854/6160586_orig.jpg

It is absolutely possible to control where the nose cone is pointed when it fires..
It's not 100% guaranteed,, but vastly improved chances that it will fire out into open air versus leaving it up to lady luck without a drogue..
Without a drogue the booster and the payload section / av bay / nose cone flail about totally uncontrolled..
Where the nose cone is pointed when it fires is a crap shoot...
Earlier in these pics is a rocket that is a good example of too big of a drogue,, the nose cone is pointed almost straight down while falling under drogue..
With the correct size drogue, nice and close to the heavy av bay the av bay will be pointed almost straight out into open air all the way down from apogee..
While the booster hangs at a 45 angle 180 degrees in the opposite direction...
Look at this series of pics..
This rocket falls from apogee like this flight after flight...
The winder / more turbulent the day, the more it moves around,, on a really calm day it just holds still,, just like you see it...

Teddy
 
Yes I slid it down the harness as you suggested. The only potential problem I see with that is that the chute will get yanked hard out of the chute protector, which can cause the harness to tear the chute protector.

BTW, it's not Nomex. I make my own chute protectors from cotton canvas fabric that I make fire resistant with a solution of borax and boric acid. Works fine, although you have to reapply the solution every time you wash the chute protector.
 
You want the chute protection anchored to the shock cord and unable to slide along it or especially up the shroud lines. Too often I've seen them slide up the shroud lines and reef the chute. That's bad.


Steve Shannon
 
You want the chute protection anchored to the shock cord and unable to slide along it or especially up the shroud lines. Too often I've seen them slide up the shroud lines and reef the chute. That's bad.


Steve Shannon

I will echo this - I have had this happen to me and my 4" Dark Star. It came in miiiiiiiiighty hot and thankfully no damage. Lesson learned - make sure the chute protection is secured!
 
I make my own chute protectors from cotton canvas fabric that I make fire resistant with a solution of borax and boric acid. Works fine, although you have to reapply the solution every time you wash the chute protector.

What approx. ratio of borax to boric? Saturated? Super-saturated?
 
We got some unusually cool, non-humid weather this week so I was finally able to get started painting. I sprayed primer today. In the past I have always used rattle can primer but that would be crazy with this big rocket. So I bought a second spray gun with 1.8mm tip to use for primer. The primer that I am using is Custom Shop lacquer primer from TCP Global (thinned 1:1 with Custom Shop lacquer thinner). The next step will be to sand the primer with 400 grit.

36296129285_976b290194_o.jpg
 
What approx. ratio of borax to boric? Saturated? Super-saturated?

Sorry for slow response, just saw your post . . .

My recipe for chute protector fire retardant is:
1/2 gallon hot water
5 oz Borax
2 oz boric acid
 
I finished many hours of primer sanding and today I started painting color coats. I like this silver paint. It looks just like metal.

36071657280_1ba4676de7_o.jpg
 
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