Madcow Mongoose 38mm Carbon Fiber Minimum Diameter Build Planning

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I read that they feed the spent mash from beer making to pigs.

It's a baby pig of some variety. Full disclosure...it's not my pig and not my beer. I don't condone serving beer to pigs. It's a waste of beer and probably not good for the pigs. It does make a cute photo though.
 
"Do a search for Jim Jarvis' thread on his 3 stage. He has successfully incorporated a WiFi switch into his CF airframe. The technique he used involves cutting a slot in the airframe."



This is information that I have been searching for, but I have failed so far. Does anyone have a direct link for this?
 
Er.......ummmmmm......well, Just make sure you don't use shearpins on the sustainer then! Kurt:bangpan::point::lol::surprised:
I don't understand what you mean by this? I've flown exactly this way for many flights without any issues.

Maybe it's something you're doing wrong? How many times have you had this type of failure?


Tony
 
Stick the Quantum inside the tubes and find out. I suspect it might have decreased range. You might have to have your device right next to the ebay to get it to work. Perhaps someone who's flown a Quantum in CF can reply?...
I tested the wifi switches in a couple of different CF tubes. In my 54mm thin-walled CF Mongoose I got enough range where I could stand close to my rocket and get the switch to work. But in my other rocket the tube was thicker, like in the 38mm Mongoose and there was essentially no communications. Without yet testing the tubing in the 38mm Mongoose, my guess is it's too thick to allow any appreciable signal through.


Tony
 
I also got one of these, and picked it up from their shop last weekend. Boxes and boxes of carbon fiber rockets were all lined up getting ready for shipping...

Has anyone else actually started building theirs yet? I've got my fins beveled and attached. They're attached with Aeropoxy ES6209, with the fillets made of Rocketpoxy. I've started designing the 3D printed sled that will hold my flight computer and battery, and got the first prototype printed, and am working on something similar for the Big Red Bee in the nosecone.

For finishing, I'll just be sanding it and applying a 2 part clear coat that I usually use on my rockets.
 
Sorry for the continued thread hijack. I seem to have a way with these things.
Yep, the animals love spent grains. I've been homebrewing large batches of all-grain beer for better than 15 years. My beer-brewing partner and I dump our spent grains in the field across from his house. Normally within 30-45 minutes a nice herd of deer are gathered around munching on the warm spent grains. They love them. I've not tried it, but I've seen recipes for making dog biscuits out of spent grains. I'll try after the next brew session and report back!

I read that they feed the spent mash from beer making to pigs.
 
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I'm wondering how much variation there is in tube weight. My body tubes weigh:

30" - 222.2 g = 7.4g/inch
16" - 117.9 g (actually 16-1/16") = 7.34g/inch

(I know I'm mixing metaphors with my units.)

The total of all the parts included with the kit is 617 grams. Heavier than I thought it would be based on my thinking it was thin walled CF, but still not too bad considering how stout the final rocket will be.


Tony
 
I'm wondering how much variation there is in tube weight. My body tubes weigh:
30" - 222.2 g = 7.4g/inch
16" - 117.9 g (actually 16-1/16") = 7.34g/inch
(I know I'm mixing metaphors with my units.)
The total of all the parts included with the kit is 617 grams. Heavier than I thought it would be based on my thinking it was thin walled CF, but still not too bad considering how stout the final rocket will be.
Tony

My package will arrive tomorrow. Perhaps I'll have some measurements to compare in the evening. The OpenRocket and RockSim models in the first post assumed that the tubes would be 7.125 g/in... so the tubes you received match that well.

2017-11-14.png

7.54 oz = 213.7554g
213.7554 g / 30 in = 7.12518 g/in
 
I received my Mongoose38 kit yesterday. The booster tube weighs 213g, surprisingly the exact number predicted.
 
Maybe getting ahead of myself, my 38 just landed on my doorstep, but I was thinking about finishing and wanting to get a wet, glossy look (I really like that fiber look).

Would a can of gloss clear coat do the job?

Thanks
Nate
 
Would a can of gloss clear coat do the job?
Yes. High temp clear will help the clear last longer against supersonic heating too. The carbon tubes also polish up quite well. I did sandpaper through 3200 grit then 3 types of Meguiar’s car polish and it looks great.

Edit: the polishing I did was on a 29mm carbon tube from Madcow, not the Mongoose 38’s. YMMV.
 
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Maybe getting ahead of myself, my 38 just landed on my doorstep, but I was thinking about finishing and wanting to get a wet, glossy look (I really like that fiber look).

Would a can of gloss clear coat do the job?

Thanks
Nate
After looking at my body tubes I don't think my usual routine of wet sanding will do it - they are too uneven. I think I'm going to try the Jim Jarvis method. I asked him how he gets his super glossy look and he says all he does to start is to mix some finishing (thin) epoxy and then applies it very lightly and then essentially wipes most of it off, leaving a very thin layer. I'm thinking for the tubes I'll put them on the rotisserie and spin them while they cure. Once that's done then the normal wet sanding and car wax should finish the look.


Tony
 
After looking at my body tubes I don't think my usual routine of wet sanding will do it - they are too uneven. I think I'm going to try the Jim Jarvis method. I asked him how he gets his super glossy look and he says all he does to start is to mix some finishing (thin) epoxy and then applies it very lightly and then essentially wipes most of it off, leaving a very thin layer. I'm thinking for the tubes I'll put them on the rotisserie and spin them while they cure. Once that's done then the normal wet sanding and car wax should finish the look.


Tony

Maybe I should clarify. The first two pics show what can be done with enough time, effort and a little luck. It involves building up multiple layers of epoxy and then progressively sanding it off. I've never tried this on a store-bought tube. I suppose it could be done, but I don't know why anyone would want to put that much effort into someone else's tube. I think if I wanted a wet-look finish, I'd probably just clear coat it (although I've never done that either).

The finish Tony is talking about is much easier. First, you sand as smooth as you care to. I have stopped as coarse as 180 grit dry sanding, but it would be better to go a little finer to get better results. Then, I just wipe on a layer of epoxy and then wipe literally all of it off. I have found that rubbing in the epoxy a little helps. After wiping off the epoxy, the tube feels dry to the touch (and there is no need to spin the tube). It's important to wipe off the epoxy to the point where you don't feel any tackiness remaining. I usually do this wipe twice, as the first wipe fills the sanding scratches a little and the result after the second wipe is better. The third pic shows the results of this approach. Most people think it looks fine, but it is not a wet look. Roughtly, it's about 75% of the result with about 5% of the work.

Any epoxy finish can be improved by polishing. I use the 3M Finesse-It II Machine Polish (although I did not use it in the finish in the third pic - it's just the epoxy wipe).

Jim

DSC01969.jpg

Fins.jpg

IMG_0706.jpg
 
Sorry for the continued thread hijack. I seem to have a way with these things.
Yep, the animals love spent grains. I've been homebrewing large batches of all-grain beer for better than 15 years. My beer-brewing partner and I dump our spent grains in the field across from his house. Normally within 30-45 minutes a nice herd of deer are gathered around munching on the warm spent grains. They love them. I've not tried it, but I've seen recipes for making dog biscuits out of spent grains. I'll try after the next brew session and report back!
When I saw "the animals love spent grains" I was getting seriously worried... Then I realized you weren't talking about propellant [emoji6]

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Maybe I should clarify. ....<snipped for brevity>

Jim
Jim,

Thank you for your post. Very helpful. I was thinking of a thicker coat but now I do recall you saying it should be pretty much dry to the touch after the epoxy has been wiped off. I'll try it this week on the shorter tube and post the results.

I don't expect it to look anything like yours though. First it's spiral wound tubing and dang, those are just beautiful looking fin cans. Mine I'm sure will be a pale imitation.


Tony
 
...I asked him how he gets his super glossy look and he says all he does to start is to mix some finishing (thin) epoxy and then applies it very lightly and then essentially wipes most of it off, leaving a very thin layer...

Tony

This is my method of "sealing" or finishing the unpainted FG rockets that I have as well. I do a final wipe with a microfiber cloth and leave just a thin film on the surface. I wipe down to an eggshell sheen with just a very slight tack left. The epoxy ends up more towards the semigloss side when cured. We have tried leaving a glossy coating on the surface and it did not work too well. Maybe you could go back with a second epoxy coat after the first has cured to boost the gloss. I have always been satisfied with just the single coat. Fixing range rash is as easy as a light sanding (1000 - 2000 grit) and then reapplication. I know some folks use car wax or other methods to give the FG a rich and finished look. I like the epoxy though.
 
Jim,

Thank you for your post. Very helpful. I was thinking of a thicker coat but now I do recall you saying it should be pretty much dry to the touch after the epoxy has been wiped off. I'll try it this week on the shorter tube and post the results.
...
Tony

The translucent FG tubes that Wildman sells look great with the epoxy. Really increases the transparency.
 
Wrong Kurt. If you have a problem you are not doing it right. Done it many times with shear pins and have not lost a motor.


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Am glad you are doing it right then because shearpins on the booster in a DD rocket certainly could allow for a higher momentary pressure spike that could kick a motor out if the tape was insufficient to hold the motor in. That is opposed to no shearpins.
I've had the experience of witnessing lost cases at launches so am a bit leery of tape. Yes I know folks use it and get away with it but you have to ask yourself, "Do I want to buy a new case if it's blown away to nether land?"

That said, I do have a project with a wimpy motor clip I'm going to use additional tape for motor retention. It's a long-necked rocket so I figured what the hay, there's plenty of room in the motor tube so I epoxied a solid bulkhead in there
so the motor is isolated from the pressure spike of the electronic deployment. I call it a little insurance for motor retention/recovery as the motor is not going to be subjected to the pressure increase. Of course as long as the bulkhead
holds. I made sure it was substantial. Kurt
 
...It's important to wipe off the epoxy to the point where you don't feel any tackiness remaining. I usually do this wipe twice, as the first wipe fills the sanding scratches a little and the result after the second wipe is better. ..<snipped for brevity>
Jim,

What do you use to wipe off the epoxy? I tried a cotton gun cleaning patch, paper towers, and microfiber. I got a lot of lint with all three even though the microfiber was well washed. I tried the paper towel after the patch so it's possible the paper towel was just pushing around the lint from that. I only did the payload section as don't have the fins mounted yet.

Thanks for your help,


Tony
 
Jim,

What do you use to wipe off the epoxy? I tried a cotton gun cleaning patch, paper towers, and microfiber. I got a lot of lint with all three even though the microfiber was well washed. I tried the paper towel after the patch so it's possible the paper towel was just pushing around the lint from that. I only did the payload section as don't have the fins mounted yet.

Thanks for your help,


Tony

I use cotton cloths from Griot's Garage. I cut them into thirds and then fold them to get a 2" cube. This is for both applying and removing the epoxy. No lint.

Jim
 
Maybe getting ahead of myself, my 38 just landed on my doorstep, but I was thinking about finishing and wanting to get a wet, glossy look (I really like that fiber look).

Would a can of gloss clear coat do the job?

Thanks
Nate

This stuff does an amazing job. And it holds up really really well to being dragged across the playa after landing. Just make sure to use a respirator when you're using it, it contains cyanide. This is what I plan on using on my Mongoose.

https://www.amazon.com/dp/B0043B7UQY/?tag=skimlinks_replacement-20

Here it is on one of the translucent Wildman FG tubes. It looks like a big piece of candy, the picture really doesn't do it justice.


bvXc5iNl.jpg
 
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I don't understand what you mean by this? I've flown exactly this way for many flights without any issues.

Maybe it's something you're doing wrong? How many times have you had this type of failure?


Tony

My thoughts are using shearpins could lead to a higher momentary pressure pulse that could kick out a "taped-in" motor. If one tapes and uses shearpins they better be certain of their tape job. That's what I meant by the statement.

Kurt
 
This stuff does an amazing job. And it holds up really really well to being dragged across the playa after landing. Just make sure to use a respirator when you're using it, it contains cyanide. This is what I plan on using on my Mongoose.

https://www.amazon.com/dp/B0043B7UQY/?tag=skimlinks_replacement-20

Here it is on one of the translucent Wildman FG tubes. It looks like a big piece of candy, the picture really doesn't do it justice.


Do you prep the surface first with fine sandpaper before shooting the clearcoat? Only way I've ever gotten the glass appearance with a rattle can is several layers of clear and doing a final wet sanding with progressively finer paper. Like starting with 1000
and working down to 2000 and even finer. All the while taking care not to take off all the clearcoat. Then use rubbing compound followed by polishing compound and then a good carwax.

Just shooting clear on the colored glass would save on the prep, primer and color coat steps. I like it. Kurt
 
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How important is it to bevel the fins?

Hate to sound lazy and like I'm trying to cut corners, but I'm shopless...

Thanks
Nate
 
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