Madcow DX3 2.6 CF build

[Tony46Scaleman]

Unboxing photos, South of kit is upsized 25” motor tube and parts.
This website & great help from Mike at Madcow got me restarted with Rockets.
I cannot come close to top quality build threads onsite
but will attempt to show all phases and appreciate all free back!

 

[Nytrunner]

What are the long wooden pieces and white tube for?

This thing's gonna scoot for sure.

 

[Tony46Scaleman]

What are the long wooden pieces and white tube for?

This thing's gonna scoot for sure.

White tube is 54mm x 25” motor K-frame (glass/Kevlar) from giant leap.
The wood strips are for Longitudinal internal fillets to bond motor tube to air frame.
They are 1/4” half round bass wood equal to 1/8” space between 54mm motor & 2.6” body.
I need to sand with 50 grit paper and get good test fit.
The challenge will be getting Aeropoxy warm enough to flow.

 

[DavidMcCann]

In the photos, it appears you have the switch band on the NC coupler, and the av bay coupler in the nosecone.... planning to switch it up?

sweet looking kit

 

[Tony46Scaleman]

Thanks- close up of wood spacer on motor mount- not yet sanded


Also based on all tread rods with ebay the short coupler is for ebay and long one is for nose cone but I have not gotten that far yet. Appreciate your comments and will lay all those parts out & photo before assembling, this is my first shot at electronics.

 

[Nytrunner]

Interesting upgrades.

Ambitious first use of electronics. Are you including a tracker in the nose?

Good luck and remember to ground test!

 

[Tony46Scaleman]

The Madcow kit is very nice!
I have several scratch built rockets that are proven good flyers on large J motors but cannot get excited to retrofit with electronis. I can fly this on smaller motors to start but want to build this kit to hold together with K550/K700; I would love to see rocket sims for this kit with large K motors.
For sure I will need tracking as this one will be high altitude and very easy to loose. Thinking about Trackimo but I know there are much better units. Also may add backup for RRC3 but I am taking my time with build focusing on lower section (motor & fins) to start.
I look forward to ground testing and then handing off to buddy with hot rod paint shop- maybe Silver Green flame design.
That seems so far away but I started this to enjoy the build. Thanks!

 

[DavidMcCann]

really rough ballpark based on my 2.6" madcow screech, K550 will do about 10,000' little over M1, 22G's. K1100T M1.2, 10K and 43G.


My screech did almost 9K, M1.somthing and 49G on a loki K1127LB.


If you leave room, I'm sure you could slide L's into this one.

 

[blackjack2564]

Ok, please explain, I don't get the 25in motor tube.
Kit comes with a 12in. long enough for any 54 motor, so why the long one with wood dowels etc.
Stiffen the airframe?

 

[Andrew_ASC]

Maybe he's got plans for a longer motor casing eventually???? :wink:

 

[blackjack2564]

Maybe he's got plans for a longer motor casing eventually???? :wink:

Umm, you already know that's not needed.
I've flown 6xl's with 10in. mounts.
Heck I've flown long motors with no mount, just 2 centering rings.

 

[Tony46Scaleman]

Certainly a bit unconventional but a few reasons I started with longer motor tube: I wanted to use hardpoint anchor to motor tube vs. Eyebolt to front motor closure, I also wanted broader spaced attachments given length of longest motor and how close 2 centering rings are to aft end. I plan to drill no holes in air frame and the challenge is how to place additional centering rings & epoxy far within 1/8" spacing- that's how I got the good or bad idea to flow epoxy along long dowels.
I am not yet committed to that plan but will build with longer motor tube and additional centering ring on forward end.
I appreciate all the input and do have a tendency to overbuild. Thanks!

 

[Nytrunner]

I take it No holes means no rail buttons?

 

[rharshberger]

White tube is 54mm x 25” motor K-frame (glass/Kevlar) from giant leap.
The wood strips are for Longitudinal internal fillets to bond motor tube to air frame.
They are 1/4” half round bass wood equal to 1/8” space between 54mm motor & 2.6” body.
I need to sand with 50 grit paper and get good test fit.
The challenge will be getting Aeropoxy warm enough to flow.
View attachment 335209

So the wood strips are dams to make fin pockets.

 

[jeff2space]

Not sure I’m following what you’re doing but maybe as you get further along with your build.


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[crossfire]

White tube is 54mm x 25” motor K-frame (glass/Kevlar) from giant leap.
The wood strips are for Longitudinal internal fillets to bond motor tube to air frame.
They are 1/4” half round bass wood equal to 1/8” space between 54mm motor & 2.6” body.
I need to sand with 50 grit paper and get good test fit.
The challenge will be getting Aeropoxy warm enough to flow.
View attachment 335209

To each their own but it seems like a lot of extra work for the benefit your going to get. Just double dip fins with epoxy and your good to go. I have seen it done on very large projects but not on this size of rocket.

 

[Tony46Scaleman]

So I will scrub longer motor tube idea, keep with the kit design for minimal weight, add 1 centering ring only to front end of motor tube and use fin slots to apply epoxy to fin roots.
Also I will get forward motor closure for shock cord attachment and have seen various techniques to prevent unscrewing. I added upgraded kevlar cords with swivels.

I planned to use Acme "glue on" rail lugs rather than buttons. I do plan to add holes for sheer pins rather than friction fit.
Thanks!

 

[patelldp]

Nut - split washer - washer.


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[AlfaBrewer]

Toothed washers are a better choice.

View attachment Split-Lockwashers-Separating-Myth-from-Truth.pdf

 

[Mendal]

Umm, you already know that's not needed.
I've flown 6xl's with 10in. mounts.
Heck I've flown long motors with no mount, just 2 centering rings.

humm no MMT now thats an interesting concept.

 

[DavidMcCann]

So I will scrub longer motor tube idea, keep with the kit design for minimal weight, add 1 centering ring only to front end of motor tube and use fin slots to apply epoxy to fin roots.
Also I will get forward motor closure for shock cord attachment and have seen various techniques to prevent unscrewing. I added upgraded kevlar cords with swivels.

I planned to use Acme "glue on" rail lugs rather than buttons. I do plan to add holes for sheer pins rather than friction fit.
Thanks!

I've done this for recovery harnesses for many rockets. it'll outlast the rocket.

I also typically drill a 1/4" vent in each booster or payload to prevent them popping off early on the way up. I thought the idea of pressure inside the rocket popping one open was crazy. then I saw a few videos of it happening and I was sold.

 

[Tony46Scaleman]

Thanks- I plan to put vent holes and thought about cord straight to motor but thought 1/8" CR (54mm inside 2.6") was too tight. I need to measure cord smashed flat. Your's looks close- maybe 54mm with 3" CR?
I appreciate all the info and now just need to wait for new CR. Thanks

A side note- I will start a separate thread when less busy for LDRS21 photos; I has press pass and got some great shots of big project for 1 day. Happy to share on individual basis for flyers I may have caught.

 

[DavidMcCann]

Thanks- I plan to put vent holes and thought about cord straight to motor but thought 1/8" CR (54mm inside 2.6") was too tight. I need to measure cord smashed flat. Your's looks close- maybe 54mm with 3" CR?
I appreciate all the info and now just need to wait for new CR. Thanks

No problem glad to share.

That photo is a 54mm mount for a 2.6" madcow screech
a few photos of the 38mm and 54mm builds i did- https://www.flickr.com/photos/31757945@N05/albums/72157647408994783/with/27689812650/

Wish I could add a flight report, but I'm waiting to fly it on a 2550 load....and I blew up the 1600 I made...so.... still working on that idea.

This is really a cool size rocket.... Should be a blast on 1706 loads.

 

[Tony46Scaleman]

Big help and great site!
Thanks

 

[Nytrunner]

54 in a 2.6, just like those three L2 attempts they never found lol

 

[patelldp]

Toothed washers are a better choice.

View attachment 335268

Glue is a better better choice.

 

[Nytrunner]

Glue is a better better choice.

Unless you want to remove aforementioned nut/screw