Chris' Punisher 4 L3 build

Last night I put a fillet on the back side of the front centering ring on the motor mount side.

Today I glued the motor mount assembly into the rocket. I put a bead of epoxy into the body tube where the front centering ring sits, slid the MMT assembly most of the way in, put another bead of epoxy just inside the back edge of the body tube and then slid it the rest of the way in. I cleaned up the little bit that squeezed out between the body tube and thrust plate with alcohol. I'll let it dry overnight and then start working on the fins.

Last night I epoxied the first fin to the MMT. I'm using 6g of Rocketpoxy per fin root(.5g/in). That seemed to work out well. From the inside of the MMT I could see about 1/8" of squish out on either side of the fin. I got another fin done this morning. I also added a fillet of epoxy on the back side of the rail button PEM nuts so the recovery system doesn't snag on them. It's starting to look like a rocket now.

I stopped by Tractor Supply on the way to work and bought some 20g syringes to do the internal fillets.

Chris you do very nice work. Can't wait to see my retainer

Thanks Gary. I should have it in the mail tomorrow morning. I had to pick up the screws from a fastener store today.

I got the last fin tacked on last night. Then I made a simple cardboard faux fin root and tried "injecting" 4g of RocketPoxy at the center. It made a fillet 3" long and about .375" radius and spilled out both ends. I think that was a bit too much.

This morning I injected my first set of internal fillets using ~1g of epoxy per inch of fin root. RocketPoxy is ~2g per mL. I'm glad I grabbed the 20mL syringes.

Its been a while since I've updated this thread. Over the last two weeks I got all of the internal fillets and 2/6 external fillets done.

I've been spending most of my time working on the bulkheads for the altimeter bay. I got them done on Monday.











Today I spent about 45 minutes sanding the coupler with 60 grit trying to get it to fit into the nose cone. I got it to the point that it will slide on, but it still sticks a little getting it on/off.

My goals over the weekend are to have the booster complete and the coupler fitted to the NC.

I've got some other parts designed that I hope to get done soon too. :wink:

I rigged up a coupler lathe on my drill press tonight. It's closer but it still isn't perfect. I think it still needs some more work.

If you try this make sure you support the bottom of the spindle. I drilled a hole in a piece of maple for the 1/4" all thread to ride in.

Thanks to Danh for spurring me to try this.

Makes for light work. I did the same with a PML coupler for my spitfire build. Nice even sanding but it got hot (the paper)

The sticky spot might be in the n/c. You might use some 400 grit in there, just to make sure.

so what do I use for paper to do it by hand?

I was using 50-60 grit and turning the coupler constantly so I didn't wind up with any flat spots.

ChrisAttebery said:

I was using 50-60 grit and turning the coupler constantly so I didn't wind up with any flat spots.

Click to expand...

You'll have to finish it with 200 or 400 wet sanded to make it smooth. I have the same problem with my 4" V2. I sanded all day with grit and didn't get anywhere. Switched to 400 wet to make it slick and it worked much better.

Adrian

I was wet sanding it with 600 before I tested the fit each time. I finally got it to the point that it was a little hard to get started straight, then I could slide it all the way on and it turned fairly freely, but not quite as free as the coupler in the body tube. It would also stick a little if I didn't pull it perfectly straight off. I came the conclusion that the polycarbonate is just a bit too sticky. I put a light coat of Johnson's Paste Wax on the inside of the NC shoulder and now the coupler slides right in, turns fairly free and slides right off. Perfect! I measured both ends of the coupler with the bulkheads in place and the NC end was .012" smaller than the other end.

I got another set of fillets done this morning. I also got the vent band glued into place with Bob Smith 30 minute epoxy.

Another project I've been working on is a drill jig for the vent and shear pin holes. There are 6x 1/8" holes at exactly 60 degree increments on the ring. Now I can drill all of the holes in the altimeter bay. Yes it's a bit OCD, but I had fun making it.

Finally, I thought some of you might find this useful. My friend and I made these epoxy caddies about 18 years ago. It's just a 4x4 that we drilled with Forstner bits. Each hole has a smaller hole that fits over the cap on the bottle. That way you can keep the bottles upside down and the epoxy is at the tip where you need it. It's really handy when it's cold and the epoxy takes forever to flow to the nozzle end of the bottle.

I like the drill guide. Someone was going to make one for a range of tube sizes.

subscribed

I cut, drilled and tapped 2x 5/16" 6061 rods to tie the altimeter bay together. I'm going to cut a 1/16" slot 1/8" deep down one side of each rod to hold the tray.

Chris,

Just curious, under a rough drogue deployment, would it be far more likely to strip the threads out 6061 rods? Meaning would it not be better to run the threaded rod through both bulkheads with acorn/stop nuts on the top, and stop nuts/wing nuts on the bottom?

Hi Justin,

Honestly, I've done the math and I feel comfortable with the design.

The 10-32 SS screws have a minimum strength of ~1900 lbs. each.

The aluminum has a breaking strength of ~1950 lbs. each. I did that calculation as a 5/16" tube with 1/16" walls. The holes are tapped 6x the diameter of the screws. Typical recommendations are to tap aluminum 2x diameter to get full strength of the fastener.

Your standard hardware store 1/4-20 all thread is good for ~1650 lbs. each.

Crazy Jim is using 3/16" all thread which is good for ~700 lbs. each on his Punisher 4.



Chris

I'm waiting on some parts to finish the altimeter bay tie rods and tray, but here's a rendering of the design. I blatantly stole Crazy Jim's switch ring idea. Thanks Jim!

The Telemetrum and RRC2+ will be mounted on 1/2" standoffs. The lipo batteries will be zip tied to the tray in between the altimeters. I'll need to cut a window in the switch ring to access the upper mounting screws on the Telemetrum.

I truly admire your work: especially the thrust ring and altimeter bay bulkheads. I have got to get my lathe and mill for retirement. Thanks for posting.

ChrisAttebery said:

I'll need to cut a window in the switch ring to access the upper mounting screws on the Telemetrum.

Click to expand...

Why the heck didn't I think of that! [as obvious as it is.]
Glad to see you ran with it, & made some nice improvements, which I will "borrow" from YOU on my next rendition.

Thanks gentlemen. I've been learning how to use Autodesk Fusion360 lately. I don't know that I would have attempted some of this without being able to visualize how everything would fit together. I also read as many build threads as possible to pick up ideas.

I got the altimeter tray and tie rods done. All that's left is the switch band.

That is the slickest av-bay ever Chris. Keep up all the cool products.

Looks good Chris!

I got the switch band notched to access the screws and terminals on the altimeters. Then I glued it to the tray with Rocketpoxy. I also marked, drilled and mounted the switches. I drilled all of my shear pin and vent holes too. All that's left is in the altimeter bay is to solder the switch harnesses up and route the antenna.

I cut a stand for the rocket this morning. I'll post some pictures tonight, but it's the same basic design I use for all of my stands.

Next up is body work, primer and paint. My least favorite parts of a build.

I've been busy making parts to fill orders for the last couple weeks, but I'm finally caught up again.

I started sanding the fillets this morning. I need to do some filling and shaping at the ends, but the bulk of them look good.

I also picked out a color scheme and started working on decals.

Today I cleaned up the fillets and then sanded the entire rocket from 100 grit down to 220. I laid down three coats of primer and then filled a few pin holes with spot putty.

I sanded the filler down and then wet sanded the entire rocket this morning. Then I applied two even coats of white primer. I'm going to let that cure until next weekend and then I do a final wet sand and then start spraying color.

I'm going to try Duplicolor Engine Enamel on this build. It dries a lot quicker than Rusto 2x and it should be tough.

ChrisAttebery said:

I got the altimeter tray and tie rods done. All that's left is the switch band.

View attachment 281040

Click to expand...

Wow. I'd like to request that your next rocket be transparent so that we can admire all of the cool metal work from the outside!