L3 - 5" extended Jart- Build Complete

[chuck5395]

Rob,
Did I share with you the start of my L3 project?
https://binderdesign.com/store/page19.html
Now who's crazy?

 

[Salvage-1]

Not a bad project there Chuck!!

Yesterday I finished drilling the holes for the connection points between the extension tube and the main body tube. 3 more machine screws have been installed.
Sanded and scored the hell out of the fin tabs and part way up the fin to allow better adhesion of the injected epoxy and fillets.
Tacked in fins with 30 min hobby epoxy and a small amount of chopped fiberglass

 

[Salvage-1]

Deployment charge testing with the red 54mm fin can. Blacked off the MMT with a sheet of cardboard.

Drogue charge 4cc of 4Fg
[video=youtube;hmPed2tPx9A]https://www.youtube.com/watch?v=hmPed2tPx9A&feature=youtu.be[/video]

Main charge 3cc of 4Fg, 3 * 4-40 nylon screws as shear pins.
[video=youtube;ahGe_m3nLMo]https://www.youtube.com/watch?v=ahGe_m3nLMo&feature=youtu.be[/video]

 

[Handeman]

Did you test any smaller charges in the drogue? I'm not really sure of your set up, but it looked like the drogue opened but the nose cone came off and went a long ways. Are you sure you won't get a main deploy at apogee?

 

[Salvage-1]

Did you test any smaller charges in the drogue? I'm not really sure of your set up, but it looked like the drogue opened but the nose cone came off and went a long ways. Are you sure you won't get a main deploy at apogee?

Yes, I did try other charges first. I had done a rough calculation that I would need 2cc (2gram) of 4Fg Black Powder for the main and drogue. After trying these, and getting no separation on the main charge, and a jump of around 3" (no tube separation) on the chute, I started biggering.

3cc (3gram) of Bp for the main, and 4cc (4gram) for the drogue does give a powerful separation, but, that is exactly what I was after.
The backup charges from the 2nd altimeter will have 0.5cc added on top of the main charges (3.5cc and 4.5cc). If we don't get separation on the first, we damn well should on the second. If they STILL haven't come apart, well... I don't deserve to keep that rocket.

The electronics bay sits between the nose cone and the main tubes. The red middle section is only a tube extension (16"+coupler) so that I can stick an M in there. The red fin can that I used for these tests is not the one that I will be using for the certification flight. They are both 5" jarts, but the red one is 54mm MMT. I blocked the MMT with a cardboard disc so that the volume of the drogue 'bay' is the same on both setups.
The two red sections came apart on purpose. On the 75mm version the middle red tube is bolted onto the fin can and cannot separate.

On the drogue test you see the electronics bay/nose cone shoot forward and the bottom two sections separate. This was as expected. The nose cone remained attached to the electronics bay coupler, since there were 3 * 4-40 nylon screws in there as shear pins.

On the main test, I wrapped the bottom coupler with blue tape so that i could see if it was just the nose cone being fired.
After the separation you can just about see the switch band and coupler still at the front end of the rocket.

The ignitor leads go through the vent holes in the side of the switch band, on these tests, the first one (drogue), ripped the wires from the clips on my launch box, and went for the ride. On the second (main chute) test, you can see the wire still remaining attached.

Nope, there is no chance of the main coming out at apogee....
but it does scare our peacock.

 

[Salvage-1]

Started the injections last night. I worked out that the fin is 9.75" long with a tap depth of about 1"
Working out a box area of 9.75*1*1, and then halving it to get the fillet area, we get 4.875 cubic inch = 24.765 cubic centimeter Therefore since 1cc = 1ml, we need 25ml of epoxy mix per internal filet.

Two pumps of the A size West System 105/206 gets me just over 30cc of mixed epoxy and chopped fiber.
After taping off all the fin slots that I didnt want a leak through, I loaded up the syringe and injected two filets.
Well, it was 85 deg in here, and the epoxy was liquid. The injections went perfectly.
5 minutes later I see it start dribbling out of the bottom fin slot... then it starts dribbling faster... oh CRAPOLA

I whizzed the whole thing outside and set it on a spindle, through the MMT, parallel to the ground. I then started to slowly spin the fin can. Around 40 minutes later, dripping has stopped. I then mask off the bottom centering ring so no leaks there, and turn the fin can so that it stands on it's fins, and left it there overnight.

When I came back to it at 3pm this afternoon, it had been sat in the sun all day and got quite warm. There were signs of drippage out of the bottom of the fin slots, but everything else that I cleaned off last night, with lots of alcohol and rags, looks fine. When I pulled off the blue tape, all the gaps around the fin slots have been nicely filled.

So, I think I turned a mess into a success. I now should have small fillets on ALL the internal joins.
Fins - MMT
Inside of Body tube - fins
fins and MMT to lower centering ring
fins and MMT to upper centering ring.
All should have a nice smothering of epoxy.


Tonight I will be starting on the RocketPoxy fillets.

 

[Salvage-1]

Yesterday I got the first pair of filets done with the RocketPoxy. I love this stuff!!

Today I got the filets finished. 86 degrees in the garage means that the epoxy has been free flowing, and nice to work with. Then, off the can went to sit on a trestle in the back of my truck canopy. A couple of hours in there at 120 degrees and the epoxy had set up nicely enough to start the next set.

All in all, quite a successful job. Not the prettiest filets in the world, but they should be strong.


Two more jobs to do and then it is cosmetic. These are re-inject internals, and install rail guides.

 

[Salvage-1]

I just go the epoxy injections finished. Nothing to see really as everything stayed internal this time.. no leaks!!! yeah!!

I dropped the amount I was squirting in to 20cc per fin edge, so 6 of those in all.

This was done outside with the fin can in direct sunlight. Within 30 minutes, the fin can had started to soak up the heat and was getting warm to the touch.
After each pair of injections, I quickly moved the fin can on to the trestle in the rear of my truck, under the canopy. The thermometer in there stated 123 degrees, so I threw in a small electric heater. This raised the temp in there to 135 degrees. I left the fin can in there for an hour, then removed it and did another set.
The whole procedure was repeated for the final pair of filets, and left the can in the 'oven' for 2 hours..

After this, I removed the can, stood it with its fins in the air and injected 10cc per hole (3). It is now sitting in the sun, because it won't fit in the back of the truck sat like this.
The idea is to make a really solid joint with the front centering ring.

No leaks.

Only things to do now are to drill holes for the rail guides. Then, I think it needs some finish work, maybe a sticker or two, and a coat of something.

 

[Salvage-1]

Holes done for the rail guides, then all 'hardware' was removed in prep for a clear coat.

It's done, and ready to fly, once I put all the hardware back in.. .

 

[OregonBAR]

Nice job! Looking forward to watching this bad boy fly ('scream') at NXRS next week....best wishes on a successful L3 flight!

 

[Igotnothing]

"The thermometer in there stated 123 degrees, so I threw in a small electric heater. "

And now we know why your truck sagged under it's own weight - you changed the temper.

Thank you for the water at NXRS. I was just about boiled dry in the head. (Which may, or may not be a starting condition.) Great to meet you and the Oregon crew. I look forward to next year.