1/2 Scale Composite Patriot Build Thread

[COrocket]

I had some larger motors in my collection that I'd like to be able to fly locally in Florida, so I set out to build a large diameter rocket that I could launch high thrust full K (maybe depending on final weight), up to small M motors and keep the flights under a mile in altitude. I've always enjoyed flying my Wildman 2.6" Patriot, so going 1/2 scale seemed like a fun project. Right now the plan is to do head end deploy and use the nosecone as the main chute compartment to keep the CG forward. I ordered a bunch of 8" diameter parts from Wildman, including a 52" booster, 25" upper airframe, coupler, 98MM motor mount, rings, and Tim was nice enough to sell me a 3:1 nosecone that I've seen on the Gizmo XL rockets for the scale look. I'll be cutting the fins and avionics bay items from scratch. All I've done so far is clean up the tube ends with sandpaper and give the parts a bath. They look good next to the 2.6" and Estes size Patriot

 

[COrocket]

While I'm waiting for a sheet of 3/16" G10 to cut the fins, I got some initial work done. The Aeropack retainer is installed with PEM nuts, top centering ring is drilled for a U-Bolt and tacked onto the motor tube, 1" switch band for the nosecone coupler is cut and glued with Aeropoxy, and fin guides are cut out of MDF to align the fins once the booster starts getting glued together.

Next up is installing the middle centering ring and filleting the top ring, cutting the fins, drilling mounts for the rail buttons, and cutting/attaching fins.

 

[COrocket]

Got the sheet of 3/16" G10, so I cut out all four fins and the first two tacked onto the booster using Aeropoxy. Two rail buttons are also drilled and attached using 1/4-20 PEM nuts

 

[Bobrogg]

what bit do you use to cut the G10?

 

[Hobie1dog]

nice looking shop, tools, and quality of work

 

[COrocket]

what bit do you use to cut the G10?

1/8” carbide Endmill. Then a sweeper attachment connected to a 5HP shop vac to make sure the dust doesn’t fly everywhere

 

[sharkbait]

I had some larger motors in my collection that I'd like to be able to fly locally in Florida, so I set out to build a large diameter rocket that I could launch high thrust full K (maybe depending on final weight), up to small M motors and keep the flights under a mile in altitude. I've always enjoyed flying my Wildman 2.6" Patriot, so going 1/2 scale seemed like a fun project. Right now the plan is to do head end deploy and use the nosecone as the main chute compartment to keep the CG forward. I ordered a bunch of 8" diameter parts from Wildman, including a 52" booster, 25" upper airframe, coupler, 98MM motor mount, rings, and Tim was nice enough to sell me a 3:1 nosecone that I've seen on the Gizmo XL rockets for the scale look. I'll be cutting the fins and avionics bay items from scratch. All I've done so far is clean up the tube ends with sandpaper and give the parts a bath. They look good next to the 2.6" and Estes size Patriot

With all that airframe, it should only need a minimal amount of nose weight to go conventional DD instead of HED

 

[COrocket]

Progress has been slow, but trying to get the booster wrapped up soon. I got the internal fillets poured with a slightly thickened Aeropoxy/silica mix, warmed up with a heat gun to help them flow a bit better. Then I got the rear centering ring glued on, and external fin and rear centering ring fillets shaped with a thicker Aeropoxy mix that stays put when shaped so I could do all the fins in one session.

 

[Glasspack]

Hows your build going ??

I have The same size 7.5" diameter kit from Public Missiles......
(not started)

Nice to see your post !

 

[COrocket]

Build is still alive, took way longer than I anticipated but the basic construction is done and the rocket is painted so I'll have to get some finished pics. I've been spending a good amount of time working on the avionics bay, which is going to be housed in the nosecone coupler essentially a head end dual deploy setup. The two body tubes are just bolted together with a coupler. Plan is to have the Cert3 XL chute in the nosecone and the drogue in the main body.

Pics are of the avionics bay, a featherweight tracker and redundant Ravens with simple circuits. Deployment is going to be using the TR Eagle CO2 system. Right now there are 4 units installed for dual redundancy on both parachute events. The plan is to utilize all four of the Raven's outputs for Main/drogue/backup main/backup drogue. Each CO2 unit can accept two e-matches, so each Raven is wired to each CO2 unit and will attempt to activate them all regardless of what the other system is doing. Running redundant e-matches help overcome certain rare dual point failure scenarios, such an example would be a system 1 computer failure and system 2 e-match failure still allowing all four CO2 units to be actuated.

Right now I'm in the process of ground testing and sizing the CO2 tanks, so more to follow soon.

 

[COrocket]

Ground testing comprised of both the main and drogue compartments being shear pinned with (4) 4-40 nylon screws.

Main chute deployment charge testing went well - Tested 16, 20, then 25 gram CO2 cartridges. Looks like I'm going to be using 20 grams for the primary and 25 grams for the backup. The 16 gram separated well, but the 20 gram gave a bit more "oomph" to push the nosecone a little further across my shop floor. Because of the short nosecone shoulder, I noticed that on the 25 gram test that the cartridge was still venting (picture 2) even after the nosecone was gone. I figure that a 25 gram backup might help build a bit more pressure if the nosecone doesn't come off cleanly with the primary charge, but there doesn't seem to be any benefit going above 20 grams for the primary.

The drogue deployment tests showed something very valuable (that I suspected but had to verify with testing) - the combination of large interior volume of an 8" rocket, the natural air leaks at airframe joints, and the 1/8" airframe vent prevented the rocket from separating during ground testing and resulted in not enough pressure building.

To correct this, I CNC'd a pair of G10 bulkheads to snuggly fit on either end of the middle airframe coupler, and drilled them to accept the same 5/16" U-bolt used on the avionics bay, as well as a pair of 5/16" all thread running the length of the coupler. This essentially replaces the U-bolt attachment point that was previously on the upper centering ring. More importantly, it reduces the length of airframe that the recovery charges have to pressurize, from 44 inches down to 9 inches (almost 80% reduction). This should hopefully reduce the drogue volume to something closer to the nosecone volume, so next step is to redo the deployment tests with this new setup. If I still can't get a reasonably energetic separation for some reason, reverting to black powder charges is the game plan.

 

[COrocket]

Got some pictures of the completed rocket done after it was painted and the decals were installed - I'm super happy with how it turned out. Weighted everything and it came out to 46 lbs without the motor. Plugged that weight into OpenRocket to get some options for the maiden flight. Right now I'm either looking at the Aerotech L1256 Super White or the Aerotech L1940 X. Should do around 2700 or 3400 ft respectively. Later on it looks like it will do just short of 5000 ft on a M1297.

 

[rfjustin]

Got some pictures of the completed rocket done after it was painted and the decals were installed - I'm super happy with how it turned out. Weighted everything and it came out to 46 lbs without the motor. Plugged that weight into OpenRocket to get some options for the maiden flight. Right now I'm either looking at the Aerotech L1256 Super White or the Aerotech L1940 X. Should do around 2700 or 3400 ft respectively. Later on it looks like it will do just short of 5000 ft on a M1297.

Nice!!!

 

[darrenf]

Got some pictures of the completed rocket done after it was painted and the decals were installed - I'm super happy with how it turned out. Weighted everything and it came out to 46 lbs without the motor. Plugged that weight into OpenRocket to get some options for the maiden flight. Right now I'm either looking at the Aerotech L1256 Super White or the Aerotech L1940 X. Should do around 2700 or 3400 ft respectively. Later on it looks like it will do just short of 5000 ft on a M1297.

Looks fantastic, can't wait to see flight reports. I too would like something to launch around 5k' for my level 3 cert. Haven't yet decided, but looks like an 8 inch rocket is a distinct possibility.

 

[COrocket]

Flew for the first time yesterday at Tampa Bay! Flew great and all the deployment events occurred as expected. Max altitude in the L1256SW was 2827 ft. Very pleased with how it flew!

Video (including commentary by the club president):