O3400 Min Diameter L3

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airforcetp1991

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Almost finished a 75mm CF MD build that will launch on the 28th of this month. Other than just wanting to fly a rocket this will test a new parachute wrap and line cutter setup for the eventual 98mm flight. The new setup uses smaller Piranha line cutters which save weight and minimize the mass swinging around after the apogee deployment. The 75mm will use the same single break design but with BP instead of Co2. Flight will be on an L-1420R to about Mach 2.5 and 28,000’ AGL.

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The new parachute wrap uses 2 15” zip ties that are linked together to allow for several wraps around the chute. This allows for a more secure wrap without sacrificing the redundancy of only needing one line cutter to fire. The picture is pretty crude but it’s about a 90% final wrap setup. This is the same 72” fruity chute that is used in the 98mm.



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airforcetp1991

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Looks like a fine rocket @airforcetp1991!

What kind of terminal blocks are you using in this picture?

View attachment 477141

I haven't seen this kind before and am intrigued.
So those are the male ends of these wire connectors. They are waterproof and have a very strong latching mechanism. I tried as hard as I could to pull one apart by the wires and couldn’t do it. I like them because it makes it easy to attach the wires that lead to the line cutters while also keeping the AvBay sealed since the male ends are epoxied to the bulkplate. The strength of the connection also avoids the issue of the shock cord twisting and pulling the connection apart. The picture below is from my 98mm AvBay but it gives a view of what they look like from the top (before epoxying).

ZoneLiStore 2 Pin Way 18 AWG Waterproof Wire Connectors Plug 1.5mm Series Terminal Connector Pack of 10 https://www.amazon.com/dp/B07MZ5LFN...abc_Z15GFXM3N17QNYGJ6K97?_encoding=UTF8&psc=1

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airforcetp1991

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75mm test was a huge success. Piranha line-cutters worked flawlessly and the onboard video worked as well. O-3400 recovery chain is now flight proven, to include the chutes, line-cutters and all electronics. Fin paint on this rocket looked cool but wasn't up to the same standard as the 98mm build which had no Mach rash of any kind on its test. I am using a higher quality epoxy clear coat on the 98mm as well. 75mm flew on an AT L-1420R to Mach 2 and about 20,000' AGL.



-Tony


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Theory

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nice

really dig seeing the progression in this thread.

lots of concepts being proven in the real world
 

Theory

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Wishing you the best. No doubt you have put in the work. Time to light that candle!
 

gerbs4me

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Wow that was one awesome flight! love the paint scheme by the way.
 

RocketScientistAustralia

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Have a look at some of the builds by cryoscum. He held the Tripoli O class commercial record for altitude and speed. O3400 to 66k' and M3.6 IIRC

Here are a couple of his threads on the Australia forum:

There should be some useful information there ;).

Enjoy the build!
The one with the stainless steel leading edge on the fins. Had lovely bluing after the flight.
 

airforcetp1991

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The one with the stainless steel leading edge on the fins. Had lovely bluing after the flight.
Thank you, I have looked over those threads extensively and it was a huge help in the design phase of this project. The “4” Build” thread was especially helpful with the fin shape considerations. I wanted to use 3 fins as well but without that level of metal work the FinSim analysis showed I needed 4. I tried to price out a way to use titanium for the LE but it was crazy expensive haha
 

MClark

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Have a look at some of the builds by cryoscum. He held the Tripoli O class commercial record for altitude and speed. O3400 to 66k' and M3.6 IIRC

Here are a couple of his threads on the Australia forum:

There should be some useful information there ;).

Enjoy the build!
Tripoli has no records for speed.

“The one with the stainless steel leading edge on the fins. Had lovely bluing after the flight.”

The use of stainless steel in fins is prohibited by the Tripoli safety code.

M
 

RocketScientistAustralia

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Thanks, I decided to go with a gloss finish for the record attempt flight. Plus it is 2 more layers of epoxy clear coat protection.

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Any imperfection will cause localised heating that may give a hot spot site for delamination to start. This could turn the carbon fiber into a hairy brush. At Mach 3.5 a small hairy brush is more draggy and hotter and causes a large hairy brush to appear. Rinse and repeat.
Your fillets are not completely smooth. Smooth out every imperfection you can before the launch. You can't do it after you push the button.
Good luck. This is a bold project. FAR is probably the right place to launch it. I wish I had access to it. It could possibly be sanctioned as a Tripoli launch if you had the support of your TAPs. I'll leave that for others..... There is no reason another TAP couldn't take it on. Have you approached the Tripoli board? They have always been helpful. If the project was fully TAPped from the begining it can be taken up by another TAP. Of course finding that TAP is the challenge.
 

airforcetp1991

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Any imperfection will cause localised heating that may give a hot spot site for delamination to start. This could turn the carbon fiber into a hairy brush. At Mach 3.5 a small hairy brush is more draggy and hotter and causes a large hairy brush to appear. Rinse and repeat.
Your fillets are not completely smooth. Smooth out every imperfection you can before the launch. You can't do it after you push the button.
Good luck. This is a bold project. FAR is probably the right place to launch it. I wish I had access to it. It could possibly be sanctioned as a Tripoli launch if you had the support of your TAPs. I'll leave that for others..... There is no reason another TAP couldn't take it on. Have you approached the Tripoli board? They have always been helpful. If the project was fully TAPped from the begining it can be taken up by another TAP. Of course finding that TAP is the challenge.
Completely agree. The fillets are smoother than they look and I smoothed out all the micro damage after the test flight. I used DragonPlate pressed plate for the fins to help with delaminating but I expect there to be ablation after the flight. The aluminum NC tip will help as well.

Overall I know there are many ways this project can fail but after the test flight, and recovery chain test in the 75mm, I feel everything is as vetted as it can be.

From the beginning this project has been about pushing the limits. I will push the button knowing I did it the way I wanted. I can’t thank everyone who has been part of this thread enough for all the wisdom and advice over the past year.
 

OverTheTop

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I have been known to use a titanium foil glued over the leading edges of fins. That might stop the airstream trying to peel your plate apart.
 

OverTheTop

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That is a very interesting idea. Do you get it from McMaster?
Purchased on the interweb from somewhere, possibly China. It was only a small quantity of foil and not very thick (can't remember exactly) so it was relativley inexpensive. It was preformed to shape and glued on with JB weld.
 

airforcetp1991

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Purchased on the interweb from somewhere, possibly China. It was only a small quantity of foil and not very thick (can't remember exactly) so it was relativley inexpensive. It was preformed to shape and glued on with JB weld.
Nice. I’ll take a look online. I have the 75mm build as a testbed so I’ll give it a try there with some of the bigger 75mm motors. Hopefully Mach 3 ish
 

MClark

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I have been known to use a titanium foil glued over the leading edges of fins. That might stop the airstream trying to peel your plate apart.
Titanium is not allowed by the safety code as "structural".
Aluminium and copper alloys are good.
You should discuss with your TAPs before using.
 

OverTheTop

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Titanium is not allowed by the safety code as "structural".
As a laminated foil over the leading edge it would not likely fit in any reasonable definition of "structural" as it is there only to keep the high dynamic pressure of the edges of the plate and not provide structural strength. I guess you would discuss it with your TAPs or RSO up-front to make sure using it would be legal.
 
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