# Kosdon 2.5 rocket

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#### tfish

##### Well-Known Member
A while back I was able to get a couple of Kosdon's 2.5" hardware sets. They are really weird looking ..after looking at 38 and 54mm stuff for years. They are pretty "klunky" ...old school. With Frank's Fast and slow formulas these case work out to K600 and K900 motors

I figured they would make a good project for Balls this year. I'd have to step things up a bit for Balls, so I bought two 4 foot pieces of tube to make some Balls worthy motors.

While I'm at it I might as well make it edgy and go min dia with thin wall FG tube and go with the CTI polycarbonate nose cone. Heck, while I'm at, might as well go with a new to me fin attachment method too!

Tony

#### tfish

##### Well-Known Member
The body is made from thin wall FG. I borrowed the fin shape from David Reese's Falcon rocket https://www.wildmanrocketry.com/ProductDetail.aspx?product=7141 I'm sure David spent a bunch of time on it's fin design! The first step was to cut out the fins, bevel them, rough up the root edge and slot the body tube. The fins were tacked on using Loctite EA 9396 Aero.

The area was cleaned with denatured alcohol and the areas taped off with tape tabs on the backside of the fins to keep the epoxy from running past the fins.

Tony

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#### djs

##### Well-Known Member
If you're going all out, why not just make it a two stager?

#### tfish

##### Well-Known Member
If you're going all out, why not just make it a two stager?
I don't like 2-stagers.

Tony

#### MClark

##### Well-Known Member
I liked the 2.5" Kosdon motors. The M3700 was quite the ride minimum diameter.
I did with Frank a thin wall case, 1/16" with threaded closures. On the pad it weighed 16 lbs with 10lbs of propellant. The name of the rocket was "Sleeps With The Lizards".
M

#### DeeRoc29

##### Well-Known Member
What's the length of those cases, Tony?

#### tfish

##### Well-Known Member
What's the length of those cases, Tony?
The Kosdon cases are 20.75" long and take 16.37" of propellant.
Not sure how long mine will end up being. Once I get it all built and figure out what chute I need. I'll figure out how much space that needs and then the rest will be motor..plus a longish portion hanging out the rear.

Tony

#### tfish

##### Well-Known Member
So fin attachment. I've seen some of Jim's post using just epoxy and no tip to tip glass/carbon reinforcement. I bought some of the Rocket Poxy and have played (built 2 mid power rockets) with it. The only real trick seems to be either roughed up surface (mechanical bond) or a clean surface (a chemical bond) For this project I wanted to try some of the 'newer' epoxy. After talking with Jim, I purchased some of the Loctite EA E-120HP in 50ml 1.69 oz tubes. I also went ahead and bought the applicator and mixing tips. I used about 2/3rds of one cartridge. I decided I did not need the applicator tips. The tip on the cartridge is a 1/4 turn to remove and replace. I could not get the glue to dispense with the gun and end up using a pencil to push each of the plungers. This was very easy to dispense. I used about 10 grams total for each of the three fin bays and had just a tad left over. I added 3 drop of black pigment just for looks.

e-120HP is much thinner then Rocket Poxy. I did add a small amount right away to each of the two fins roots I was working on. I wanted to sort of wet things out. I ended up waiting about 45 minutes in 81 degree shop temps until the epoxy set up to the consistency of silicone caulking. Then I laid it in and smoothed it out with a "tongue depressor.

I let it sit for about 10 min more and then smoothed it out with a gloved finder dipped into denatured alcohol.

After a 5 minute wait pulled the tape and a final smoothing ..gloved finger alcohol. It came out really smooth. Each end of the fin was easy to sculpt.

Tony

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#### 3stoogesrocketry

##### Well-Known Member
So fin attachment. I've seen some of Jim's post using just epoxy and no tip to tip glass/carbon reinforcement. I bought some of the Rocket Poxy and have played (built 2 mid power rockets) with it. The only real trick seems to be either roughed up surface (mechanical bond) or a clean surface (a chemical bond) For this project I wanted to try some of the 'newer' epoxy. After talking with Jim, I purchased some of the Loctite EA E-120HP in 50ml 1.69 oz tubes. I also went ahead and bought the applicator and mixing tips. I used about 2/3rds of one cartridge. I decided I did not need the applicator tips. The tip on the cartridge is a 1/4 turn to remove and replace. I could not get the glue to dispense with the gun and end up using a pencil to push each of the plungers. This was very easy to dispense. I used about 10 grams total for each of the three fin bays and had just a tad left over. I added 3 drop of black pigment just for looks.

e-120HP is much thinner then Rocket Poxy. I did add a small amount right away to each of the two fins roots I was working on. I wanted to sort of wet things out. I ended up waiting about 45 minutes in 81 degree shop temps until the epoxy set up to the consistency of silicone caulking. Then I laid it in and smoothed it out with a "tongue depressor.

I let it sit for about 10 min more and then smoothed it out with a gloved finder dipped into denatured alcohol.

After a 5 minute wait pulled the tape and a final smoothing ..gloved finger alcohol. It came out really smooth. Each end of the fin was easy to sculpt.

Tony
Looks great Tony . What are you going to use for a liner and casting tubes?

op:

#### MClark

##### Well-Known Member
Looks great Tony . What are you going to use for a liner and casting tubes?
For these cases the US Rockets 54mm tubes fit perfectly as liners and cast into the couplers. Good luck finding those.
Triano had a lot of Frank's stuff,

M

#### tfish

##### Well-Known Member
For now I'm just going to be using tubes from Balsa Machine service.
T70H-34 2.245x2.175x.035x34in long (white Heavy wall) $5.00 C70-34 2.172x2.104x34in T70 or T70H coupler stock$8.00

I'm just going to playing with Swamp Gas in the above tubes for now.

o-rings are ...#226 2.25"OD, .125" thick.
Internal snap rings HO 225 (?)

Tony

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#### tfish

##### Well-Known Member
The electronics are in the CTI poly carbonate nose cone. RC3, Raven 3 w/ simple circuit, Eggfinder and 2 screw switches. It's not totally done but close.

Tony

Is that Trex?

#### dixontj93060

##### Well-Known Member
Nosecone electronics is a work of art. Great job Tony; what a nice mix of old school Kosdon, and everything else. &#128079;

#### tfish

##### Well-Known Member
Dan: Similar..not as heavy all plastic and air. easy to work with.

Dixion: yep might even go with tape thrust ring (kidding) I'll be turning it away from old school with some cool carbon fiber nozzle material.

Tony

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#### Steve Shannon

##### Well-Known Member
TRF Supporter
Dan: Similar..not as heavy all plastic and air. easy to work with.

Dixion: yep might even go with tape thrust ring (kidding) I'll be turning it away from old school with some cool carbon fiber nozzle material.

Tony
Tony,
That video appears to be unavailable, at least to me.
Steve

Steve Shannon

#### Jimmy F.

##### Well-Known Member
I use tape thrust rings and tape motor retention all the time, But then I have a long going love affair with snap ring hardware.

#### tfish

##### Well-Known Member
Tony,
That video appears to be unavailable, at least to me.
Steve

Steve Shannon
my bad..it was one of my locked videos..should work now..

Tony

#### Steve Shannon

##### Well-Known Member
TRF Supporter
my bad..it was one of my locked videos..should work now..

Tony
Now it works, thanks. I always enjoy your videos. How did you fabricate that nozzle? Does the texture have any effect on the flow?

Steve Shannon

#### tfish

##### Well-Known Member
I bought a 24" nozzle on ebay. I've had several people look at the material and nobody is sure what the material actually is. It appears to have two different sizes of carbon fiber cloth in a graphite matrix. Anyway, it's really strong, easily machined, smoother then it looks and was fairly cheap. I've ran 4 static tests with the same nozzle and purposely left the entrance to the throat sharp. It's still sharp after 4 firings.

Tony

#### Steve Shannon

##### Well-Known Member
TRF Supporter
Wow, that seems promising. It would be nice to know how to recreate it.

Steve Shannon

#### DeeRoc29

##### Well-Known Member
Looks awesome, Tony. I've always liked your style. Wish I could go to Balls to see it. I'll be at XPRS, though.

#### 3stoogesrocketry

##### Well-Known Member
I bought a 24" nozzle on ebay. I've had several people look at the material and nobody is sure what the material actually is. It appears to have two different sizes of carbon fiber cloth in a graphite matrix. Anyway, it's really strong, easily machined, smoother then it looks and was fairly cheap. I've ran 4 static tests with the same nozzle and purposely left the entrance to the throat sharp. It's still sharp after 4 firings.

Tony
Tony , any chance you had a IR reader to see how hot the nozzle got ?

Eric

#### tfish

##### Well-Known Member
Tony , any chance you had a IR reader to see how hot the nozzle got ?

Eric

Tony

#### ECayemberg

##### Well-Known Member
Whoa, I'm late to the party; but loving this project, Tony!

Sooo....you've got me curious. Going to keep the motor length in the "L" range, or leave that tube stock long enough to squeak an "M" out of the 2.5" hardware? Regardless, great work!!!

#### Red Phenix

##### Well-Known Member
I'm so subscribed. Tony, thanks. I learned so much from you and your videos.

Cheers and thanks

#### rfjustin

##### Well-Known Member
A tfish build thread... just like back in the day on the TQC board.

#### tfish

##### Well-Known Member

I really meant to add a tape thrust ring to the motor...but grabbed the spool of carbon fiber tow by accident and made a boat tail of sorts

Made a casting rack and packing tool for the grains. The ID of the casting tubes is 2.1 as compared to 1.78ish for 54mm grains. The motor case's .125 wall thickness, eats into the "advantage" of this motor "class".

I also put .375" shoulders on the FC and nozzle and added a second o-ring to them. The Kosdon Catalog shows 16.37" of propellant in this case. I did not mess with any of the links and my measurements are showing 16" of propellant. Frank must have had an interesting way of making it all fit!

Tony

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#### ECayemberg

##### Well-Known Member

I really meant to add a tape thrust ring to the motor...but grabbed the spool of carbon fiber tow by accident and made a boat tail of sorts

Made a casting rack and packing tool for the grains. The ID of the casting tubes is 2.1 as compared to 1.78ish for 54mm grains. The motor case's .125 wall thickness, eats into the "advantage" of this motor "class".

I also put .375" shoulders on the FC and nozzle and added a second o-ring to them. The Kosdon Catalog shows 16.37" of propellant in this case. I did not mess with any of the links and my measurements are showing 16" of propellant. Frank must have had an interesting way of making it all fit!

Tony
Indeed! Flew a J180 Dirty Harry last month. Had to trim the grains a tad; plus gouge out the forward grain enough to accommodate the stock delay which was significantly longer than the well. It was flown as a plugged motor, so I suppose I could've trimmed the delay, but it was more fun this way!

Don't recall doing any trimming of the Kos's 2.5" loads, but I only had the 1350 and 3300 hardware.

Love the tow boat tail!!!