Madcow Terminator L3 Build

richP said:

....Sand/Bondo/primer, Sand/Bondo/primer, Sand/Bondo/primer.

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I feel your pain.

Would you mind sharing where you got what appears to be a fillet sanding tool that is present in the last picture in your post above?

wsume99 said:

Would you mind sharing where you got what appears to be a fillet sanding tool that is present in the last picture in your post above?

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I believe what you are asking about are (these) contour sanders. You can find them at many online eTailers.

Tobor said:

I believe what you are asking about are (these) contour sanders. You can find them at many online eTailers.

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Yep, that's them. I originally used them to round-over fins accurately. While the largest one was still too small to do the fillets on this particular rocket, it did work well for profiling the front and back of the fillets.
I used a socket for the rest.

Thanks for the feedback guys [emoji106][emoji106]
My set should arrive tomorrow.

Did a bit of work tonight, but called it early due to having a charity century bike ride in the morning. First, I made a backing of 1/4" ply for the nosecone bulkhead. I was entirely happy with the 1/8" bulkhead that I had for the nosecone. I'm sure its just me and it was quite capable of withstanding ejection forces, but I wanted a little more thickness to strengthen and give a larger glue surface area. After seeing the recommendation by JDcluster, I made my own modification.


I then went about throwing on a first coat of primer on the fins in order to reveal how much additional work will be needed to smooth-out the imperfections. I am happy to say that it "should" only take another 2 cycles of Bondo/primer to get it ready for paint. Fingers crossed.



More questions for the knowledge-base here.
- I am planning on gluing-in the coupler to the nosecone, as opposed to using PEM nuts. Other than tightening the aluminum tip, is there any other reason why its advantageous to be removable ?
- I haven't done any calculations to verify, but I would imagine that (3)2-56 for drogue and (3)4-40 shear pins would probably be the optimal configuration. My OCD, however, just doesn't allow me to use two different sizes. Is it really that bad to use just the 4-40 for both? Basically, its a 5" diameter, 25 lb. rocket.

[/QUOTE]More questions for the knowledge-base here.
- I am planning on gluing-in the coupler to the nosecone, as opposed to using PEM nuts. Other than tightening the aluminum tip, is there any other reason why its advantageous to be removable ?
- I haven't done any calculations to verify, but I would imagine that (3)2-56 for drogue and (3)4-40 shear pins would probably be the optimal configuration. My OCD, however, just doesn't allow me to use two different sizes. Is it really that bad to use just the 4-40 for both? Basically, its a 5" diameter, 25 lb. rocket.[/QUOTE]



I used the nose cone coupler for a second tracker. Having it removable was essential when I needed to deal with the Al tip after it was knocked loose. I used 3 4-40 pins for the main and no pins on the drogue.

I would not glue the coupler in.

richP said:

So, I've decided on a Madcow Terminator for L3. While not being very familiar with fiberglass , i did read the thread on epoxy, and with some West Systems, Rocketpoxy and some 120 grit paper, I feel as though it should be too difficult to get good/strong bonding.
The kit came in last week, and my first chore was unboxing and washing everything with hot water and soap. I was very impressed with the quality of the cuts, everything looked square with smooth edges. Madcow did forget to ship the tailcone CR, but was quick to ship a replacement when I let them know.
View attachment 389112

Then it was on to the MMT work. I ordered a few extra CRs for this kit, so that i could double-up where needed. The FWD CR will have (2) 1/4" stainless ubolts and will be doubled. Next 2 CRs will frame the forward fins. 4th and tailcone CR will frame the aft fins.

View attachment 389119

While I had the rocketpoxy mixed for the fwd CRs, I was able to bond the AV bay bulkheads too.
View attachment 389125

That's it for today, will let these cure overnight.

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I'm also a fan of having my fins "trapped" between rings, just adds additional lever arm for strength. Another way of achieving similar is using lightweight material for fin pockets extending to centering rings at both ends of the motor mount tube, eliminating the additional rings. Doubt it really saves much as far as rear end mass, but it makes for easier/tighter/more easily aligned assembly especially when installing inline fins..Just add "dams" @ fore and aft positions before filling pockets with epoxy.

I only do shear pins on the NC joint. I like to make the NC coupler removable just encase I want to add other items later ( probably never happen) it's nice to know you can still get in there without a demo saw.

Due in part to y'all reponses, the nosecone coupler will be removable, using PEM nuts. The bulkhead was epoxied in tonight, and that concludes all of the major "glue work" for this build. I wound-up insetting the bulkhead about 4 inches into the coupler.


Will probably be ordering shock-cords and chutes this week; along with sanding.

Continuing along...
Finished-up the wiring in the AV bay. Doghouse Rocketry kits really do make it easier, and much cleaner than I'd be able to do myself.


Drilled some holes for shear pins.


And finally, motor case has arrived. An Aerotech RMS 75-6400. Big thanks to Tim over at Wildman for getting this out to me, and gracefully dealing with my impatience.



Ejection charge testing will start today. Fruity Chute Iris is scheduled for delivery next Tuesday, so I'll be using a rolled-up towel. Maybe even get some paint on this week.

In the home stretch. Did ground testing this weekend and got some good results. The charge for the drogue sent the forward half about 8' , and since the back end was immobile, I figure it is enough given the weights of the pieces. In the air, I'm sure it'll go the full length of the shock cord (30').
For the main, I got full extension of the 25' cord, and rather than slightly reduce the charge, I will z-fold the cord and use masking tape to keep it together. That should provide for some shock absorption. The main chute was also increased to 84", due to the rocket being a bit heavier than I initially anticipated (29lbs. with motor case).
I also got a finish coat of primer on the entire rocket, however, the weather forecast looks like it will be cold and humid for the next week at least. I might have to fly my cert flights without paint, and get that done afterwards (should everything go well).

Stickers also came in from stickershock.com, but they will have to wait until after final color coat is on.



I may increase the shock cord lengths a bit (25'/30' to 30'/35'), but haven't decided whether the added length is a benefit against stressing the connections or am increase in risk of tangling.

Been a while since my last update. Basically, I finished-up painting, and then polished with 1500, 3000 and then a few different polishes. I can out pretty good, but then I attempted to apply the stickers. I haven't done stickers this large before, and really should have taken my time and read thru instructions. I wound-up with some fairly large bubbles that just couldn't be resolved cleanly. Removing the stickers resulted in paint being torn off too..
So, I sanded down the problem areas and repainted, ordered new stickers and did it all again. I cannot stress enough how much some soapy water helps in the sticker application process. Anyways, let the paint dry for a few weeks, polished again and reapplied stickers. Much better results this time around. A little more polishing now, and I should be all done. It's not perfect, but looks good despite the repaint.
I haven't decided whether or not to clear coat just yet.
Waiting to hopefully let her fly this month, if weather cooperates.

WOWZERS! THAT IS PHENOMENAL! very well done!

what is the final weight? more or less what you were expecting?

Sweet! I like the paint layout.

Theory said:

WOWZERS! THAT IS PHENOMENAL! very well done!

what is the final weight? more or less what you were expecting?

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Pretty close. I am at just under 29lbs. with motor case. I added quite a bit of reinforcement and beefier hardware, which easily added at least a pound or 2.

richP said:

Pretty close. I am at just under 29lbs. with motor case. I added quite a bit of reinforcement and beefier hardware, which easily added at least a pound or 2.

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rodger that! i build mine the same way, and they always come out a touch on the heavy side. ...and 29 pounds is nothing a 75mm motor cant handle!

richP said:

Due in part to y'all reponses, the nosecone coupler will be removable, using PEM nuts. The bulkhead was epoxied in tonight, and that concludes all of the major "glue work" for this build. I wound-up insetting the bulkhead about 4 inches into the coupler.
View attachment 394121 View attachment 394122

Will probably be ordering shock-cords and chutes this week; along with sanding.

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Impressive bead of epoxy on that NC bulk head. I do mine like that as well by using centrifugal force "spinning" the piece to get it just right.

This is the NC on my PAINKILLER 6 (Shameless plug) Kits are now shipping PAINKILLER 6 KIT

Rich, that looks incredible. Good luck on your L3 flight!

Prepping the electronics for flight. What's the consensus for drogue delay between the primary altimeter and the backup? I am seeing conflicting times, but usually either 1s or 2s.
The 1s crowd saying that it is virtually impossible for the 2 charges to go off simultaneously.
While the 2s crowd saying that the extra second guarantees that the 2 charges don't go off simultaneously.
Using identical RRC3 altimeters. Wish there was a 1.5s setting!

richP said:

Prepping the electronics for flight. What's the consensus for drogue delay between the primary altimeter and the backup? I am seeing conflicting times, but usually either 1s or 2s.
The 1s crowd saying that it is virtually impossible for the 2 charges to go off simultaneously.
While the 2s crowd saying that the extra second guarantees that the 2 charges don't go off simultaneously.
Using identical RRC3 altimeters. Wish there was a 1.5s setting!

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I would prefer a 1.5 second setting as well on my RRC2.
When I fly an altimeter I can program more freely, I go 2. The reason is, I want to give the nosecone flopping around in the airstream a chance to yank the chute out so when the backup fires, it's just a visual and aural cue that the drogue is out and there isn't a chance of tube overpressure.
Are you going to friction fit your fin can to your av bay or are you using screws? There is less of a need for a backup charge with friction fit, so if you're using screws, a longer delay errs more on the side of caution and not blowing your airframe apart.

richP said:

Prepping the electronics for flight. What's the consensus for drogue delay between the primary altimeter and the backup? I am seeing conflicting times, but usually either 1s or 2s.
The 1s crowd saying that it is virtually impossible for the 2 charges to go off simultaneously.
While the 2s crowd saying that the extra second guarantees that the 2 charges don't go off simultaneously.
Using identical RRC3 altimeters. Wish there was a 1.5s setting!

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1 second is plenty. Here is a 4" L3 rocket with (2) RRC2's on board, one set for apogee +1.

Jump to 3:15 in the video, the ob-board video shows both events.

Well, I was finally able to get this thing launched today at URRG in Potter, NY. Since it is almost a 5 hour drive for me, I drove in last night and stayed local. In the AM, I went to the site and began prepping for a shake-down flight. The weather was a bit chilly at 28 degrees, and wind was fairly calm at 5mph. The test motor is a CTI L820 Skidmark. Flight went-off without a hitch and recovery was pretty easy. landing approx. 1/4 mile from the pad. Altitude peaked at 4250, and max. velocity was 529 fps.


Next was prepping for my L3 flight. It took much longer than I anticipated. Partially due to a stuck nozzle from the previous flight. After about 3 hours, I was ready for launch.


The wind had picked-up a bit, to about 9mph just before the launch, and the rocket weather-cocked ever so slightly into the wind. Overall however, the flight was as good as I could have made it. SIM'ed altitude was 9979' at 937fps. Actual altitude came in at 9962' at 925fps. The rocket's chutes deployed perfectly, and it landed very softly approx. 1 mile from the launch site.


So, a successful L3 flight! There are a few minor scratches in the paint, but otherwise, it held together beautifully. Its now time for a beer, and clean-up day tomorrow.
A big thanks to all that helped throughout this process, advice given on this forum helped tremendously. Shout-out to Tim Lehr at Wildman for assisting with the motor casing, Mark Hayes at Stickershock for his artwork and Mike Dutch at URRG for his sign-off and advice.

Nice, congrats!

Beautiful rocket, and a perfect flight for L3! It don't get any better than that! Congrats on a successful L3 cert!

AWESOME, and CONGRATS on the L3!!!!

Very happy to see this project conclude with a pair of successful flights. very well done my friend

Big congrats.

Congrats on the L3. Great looking rocket and sounds like a great flight too.

Congratulations!