Madcow Cowabunga Mammoth build

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Did you get the L1115 yet? I am eying that up for my Mega Nuk. Hoping Ken can get me one.
 
Did you get the L1115 yet? I am eying that up for my Mega Nuk. Hoping Ken can get me one.

I ordered it from AMW to be delivered to the sod farm this weekend. AMW website said that they had 3 in stock. It is the CTI 4 grain 75mm Classic. Sims at about 4100 ft. I want to be able to clearly see the deployments on this first flight. After the first flight I will probably use mostly M motors with this rocket.

I'll be at the sod farm this weekend but not until Sunday because we're busy Saturday.

I also ordered a K1200 White Thunder for the first flight of my Square Rocket.
 
Wet sanding in progress. This is 1000 grit. After this is done I will sand it again with 2000 grit.
45076483682_7ab32b4294_o.jpg
 
NAT
JUST A GREAT JOB. IS THE NOSE CONE ON THE COW FW WITH A COUPLER?

The nose cone is fiberglass but it is hand-laid fiberglass, not filament wound. The nose cone and shoulder are a single part so there is no separate coupler. The bulkhead is 1/2" plywood. Even though it isn't FWFG it is well made. There were seams up both sides from the mold that required filling with Bondo putty and sanding.
 
The nose cone is fiberglass but it is hand-laid fiberglass, not filament wound. The nose cone and shoulder are a single part so there is no separate coupler. The bulkhead is 1/2" plywood. Even though it isn't FWFG it is well made. There were seams up both sides from the mold that required filling with Bondo putty and sanding.

I should have just reread your first post and I would have had the answer. It would be nice to have it FW than one could do HED.
Can`t wait to see your Cow in flight.
 
I just now finished 2 weeks of sanding and polishing. The finish turned out pretty awesome if I do say so myself. It's the same Ice Pearl that I used on the square rocket but it looks much more impressive in a dark color. Photos coming soon. I plan to bring to MDRA in November for display. First I need to devise a way to transport it in my trailer without it bouncing and sliding around. I think I'm going to build some sort of padded cradle for transportation.
 
Lovely work as usual. What is the pad weight going to be?

-Matthew
My initial estimate from weighing components was 55 lb but I need to weigh it again now. Those 11 coats of paint added some weight (actually most of the primer and probably half of the clear coat got sanded off).
 

That look fabulous! I finally got a sense of the size of the behemoth with you holding it.

Sorry if this is in the thread already, but how does the stability margin? Did it need nose weight?

I am so excited for Higgs Farm to open this year! Keep hoping I’ll hear something...
 
That look fabulous! I finally got a sense of the size of the behemoth with you holding it.

Sorry if this is in the thread already, but how does the stability margin? Did it need nose weight?

I am so excited for Higgs Farm to open this year! Keep hoping I’ll hear something...

I didn't add any nose weight. But the chute deployment system that I added is forward of the CG so that increased stability a bit. Stability in OpenRocket is about 0.8 cal with a big motor and than is fine for a rocket with this much base drag. I'll be careful to only fly it with motors that get it plenty of velocity off the rail.
30541535387_694de1b11e_o.jpg
 
Last edited:
Again, really amazing work! How does that Ice Pearl stuff work (in terms of mixed with what)?

As with any dry flake or pearl, you just mix it with clearcoat and spray. If you want to get fancy they sell special intercoat carrier that you can use instead of normal clear but clear works fine for me. I mixed a tablespoon of pearl in 750 ml of clear lacquer. When spraying flake or pearl you have to be careful to evenly overlap passes and maintain a steady speed and distance because you only get one chance to get it right. You also need to be sure to remove the filter from the gun otherwise it will instantly get clogged with flakes (yeah I've done that).
 
Last edited:
As with any dry flake or pearl, you just mix it with clearcoat and spray. If you want to get fancy they sell special intercoat carrier that you can use instead of normal clear but clear works fine for me. I mixed a tablespoon of pearl in 750 ml of clear lacquer. When spraying flake or pearl you have to be careful to evenly overlap passes and maintain a steady speed and distance because you only get one chance to get it right. You also need to be sure to remove the filter from the gun otherwise it will instantly get clogged with flakes (yeah I've done that).

What gun do you use for it? I have an Iwata RG-3L with a 1mm needle. I'm a novice when it comes to spray equipment.
 
As with any dry flake or pearl, you just mix it with clearcoat and spray. If you want to get fancy they sell special intercoat carrier that you can use instead of normal clear but clear works fine for me. I mixed a tablespoon of pearl in 750 ml of clear lacquer. When spraying flake or pearl you have to be careful to evenly overlap passes and maintain a steady speed and distance because you only get one chance to get it right. You also need to be sure to remove the filter from the gun otherwise it will instantly get clogged with flakes (yeah I've done that).

Oh, cool. I looked but wasn't sure that it was dry flake. I've used chameleon flake from https://www.paintwithpearl.com/ before, so I'm familiar.

As always, you did an amazing job with that stuff!
 
What gun do you use for it? I have an Iwata RG-3L with a 1mm needle. I'm a novice when it comes to spray equipment.

1mm is too small. I used a TCP Global gun with 3mm tip. For standard size flake you would need an even bigger tip.
 
I didn't add any nose weight. But the chute deployment system that I added is forward of the CG so that increased stability a bit. Stability in OpenRocket is about 0.8 cal with a big motor and than is fine for a rocket with this much base drag. I'll be careful to only fly it with motors that get it plenty of velocity off the rail.
30541535387_694de1b11e_o.jpg
Though this behemoth is far from short or stubby, I think short and stubby stability rules apply. You'd most likely be fine with as little as an 8-inch margin.
 
1mm is too small. I used a TCP Global gun with 3mm tip. For standard size flake you would need an even bigger tip.


3mm is huge. I spray standard flake with a 1.8, no problems. 3mm is too big, and just creates more work in getting things flat again, as well as wasting whatever carrier you are using for the flake.

The end result looks nice, but that looks like a ton of excess work. That rocket looks like a 1 day polish to me, definitely, and to perfection. 1000 film on a DA, wet,
with some hand work in the corners and edges, wet, then to 3000 Trizact, wet, then to compounds on a pneumatic polisher, and finally, a bonnet if you are really a perfectionist. I hate to be a critic, but if you look at your pic of the 1000 sanding that you posted above, it is very scratched up for 1000 grit. That is the edges of the paper doing that. It should look very uniform. You obviously take pride in your paint, and are passionate about it. There is a next level. The question is, if this finish were on a million dollar super car, would you be happy? With the effort you are putting in, it should look like it.

https://www.onallcylinders.com/2015/02/23/monday-mailbag-tips-spraying-metal-flake-paint/

 
My mistake, I meant 1.3mm tip, not 3mm tip.

I probably could have done the polishing in one day since I do that by machine (Porter Cable 7424). What takes me forever is the sanding which I do all by hand. Especially the 1000 grit. As you can see in that sanding photo a had quite a bit of orange peel in the clear coat to sand out this time. Once I get it smooth the 2000 grit goes pretty fast.
 
My mistake, I meant 1.3mm tip, not 3mm tip.

I probably could have done the polishing in one day since I do that by machine (Porter Cable 7424). What takes me forever is the sanding which I do all by hand. Especially the 1000 grit. As you can see in that sanding photo a had quite a bit of orange peel in the clear coat to sand out this time. Once I get it smooth the 2000 grit goes pretty fast.

It’s still better than 90% of us will ever have.
 
My mistake, I meant 1.3mm tip, not 3mm tip.

I probably could have done the polishing in one day since I do that by machine (Porter Cable 7424). What takes me forever is the sanding which I do all by hand. Especially the 1000 grit. As you can see in that sanding photo a had quite a bit of orange peel in the clear coat to sand out this time. Once I get it smooth the 2000 grit goes pretty fast.


I was speaking of the entire process of sanding and buffing, as 'polishing. Some finishes do not give the broad window of time for polishing that nitrocellulose does. The urethanes and catalyzed polyester that I use can be efficiently polished for only abut 48 hours, the urethane for a little longer, but beyond that, they get hard fast, and no longer polish easily, or as well. With nitro, there is a wait time for the last clear coats to cure, prior to polishing, or the finish will shrink back and lose what was gained, but the windo of time for cutting and polishing relatively long.

The key to using an orbital for cutting is that the pad needs to be stopped as it contacts the finish, or it will scratch and or dig in. And, the pad needs to be kept moving. Keep it wet while sanding, Behlens makes a great lube for this, it might be called 'steel wool lube', I do not recall, as one container will last a LONG time. You only need a few drops of it for a job. After the 1000, there is no need for 2000, assuming a true sanding at 1000 with no deeper gouging from the edges of the paper. The 3000 trizact cuts fast, but it is 3000 grit. This is a special abrasive that does not easily clog, and the abrasive fractures sharp, so it lasts a long, long time. One sheet of 3000 trizact might be able to wetsand that whole rocket (3000 grit only, of course) I can almost guarantee you that if you try it, after about 10 seconds of sanding with it, and a wipe dry, you will have a big grin. Hours saved, and quality way up. The 3000 trizact on an orbital is very forgiving, and with a little practice, will give you the confidence to cut with the 1000 on an orbital.
I did notice the orange peel, but was unsure if that was due to your process in working with the flake, or if it was due to your method or mixing, or gun settings, in spraying. If you cut the carrier and flake back to flat prior to the last coats of clear, then it was probably from spraying a bit dry. A good gun helps. Iwata or Sata are good brands, and worth the cash. I have 3 Iwata LPH-400 guns with needle /fluid tips from 1.2-2.0. Spraying right to the point where it wants to sag, just prior to, helps get a glassy 'out of the gun' finish. Adjusting the amount, or type of reducer can also help. The gun settings also play in significantly into being able to safely spray to that glassy place without running. Equally important as all of this, and rarely mentioned, is the air supply for the gun. Assuming that you are spraying a gravity HVLP gun, this 'High Volume Low Pressure' gun must have a high volume of air. This means air regulators with at least 3/8" fittings, 1/2" better, a sufficient compressor, short runs of hose, I use larger i.d. hose, a high pressure at the main regulator, 60-90psi, and a quality regulator at the gun handle. These things right there, especially the gun regulator, will help you spray a glassy finish. But you probably already knew all of this.

Cheers.
 
Last edited:
I built this for transporting big rockets in my cargo trailer. I don't want to lay them on their fins because a long bouncy ride in the trailer might crack a fin joint. Nose cones and payload sections aren't a problem because I can just roll them up in blankets. A 2x4 fits nicely through a 98mm motor tube.

44616147725_3de1451fae_o.jpg
 
My initial estimate from weighing components was 55 lb but I need to weigh it again now. Those 11 coats of paint added some weight (actually most of the primer and probably half of the clear coat got sanded off).

I apparently made a big mistake somewhere when I originally weighed all the components because after I weighed the finished rocket it ended up weighing about 75 lb with motor, 20 lb more than my original estimate. Stability is still good. So first flight is now planned with a M motor. I have a CTI M1400 Classic and a CTI M1770 Skidmark in the motor box. The M1400 actually has more initial thrust and more total impulse than the M1770 so I will probably use that. The thrust curve of the M1400 will give it a better than 5:1 thrust ratio for the first 2 seconds of flight. OpenRocket says it should leave the rail at 62 fps and reach 3600 ft. Weather permitting I will fly it at MDRA on 11/18.
 
Back
Top