First post - 3D printing, cluster engines and a GoPro.

Hello all

First post. I've not made a rocket in almost two decades. However, I have 3 year old twins and they thinks its mighty awesome, so I'm back in the game. I made two Alpha 3s for them, an Estes Renegade-D for me. Now, I want to launch my GoPro and see what I see.

So, I'm getting a 3" tube and using my Makerbot for the rest. Currently I'm printing a boat tail combination dual engine housing and fin assembly. The nose cone will house the camera and be printed next.

I went dual 24mm engines because I will exceed the weight rating for a D engine. I have no experience with anything larger, so I thought clustering would be my best bet.

Question: the 3D print won't be perfectly smooth, what would you use as filler to be sanded flat?

Also, any other thoughts and comments would be appreciated.

I'll update more when the parts are done printing over the next few days (this assembly will take 26+ hours).

And below is the start of the 3D print. Note, that plinth its on is just to level the build plate and easily snaps off.

I have used Bondo to smooth PLA rocket parts.

Hi and Welcome!

I've worked with both PLA and ABS...

Getting the PLA smooth was a PITA, that stuff is really hard. I understand though that the parts can soften in a hot car, and may be problematic on high heat applications.

For the ABS, I painted the part with acetone to fuse any exposed joints together, then sanded the part smooth. This has yielded some pretty nice results for me.

All The Best!
Jim

Hello and welcome to the best place to get information and learn about rocketry..
It is way too cool that you get to do this with your children...
They will grow up flying rockets with their pop....
If I may offer some advice,,
Go with a straight 29 mm motor mount...
It's super easy to use and you'll more likely be able to
fit enough impulse in it to lift the camera..
Apples to apples any given amount of impulse will be less
expensive then lighting two 24 mm motors too...
The route you have taken is super cool because it's a bit more complex,, a cluster...
You are correct in that you seem to want simplicity until you have some experience under your belt...

Teddy

Thanks to everyone that replied so quickly. Great suggestions.

ONEBADHAWK​, I decided to stay away from E & F sized engines as everything I see online says that I need a different launch pad and controller (to be fair, I want to make a new controller from scratch, but that's another thread). However, we'll see how my test launches go, I might be getting new equipment!

I'll update this thread with pictures of the print. I'm not sure if it will be complete by the time I leave work later today, so it might be until after the weekend.

Again, thanks for any / all responses... keep 'em coming!

Well, I came into work this morning, and for the second time one of the fins separated from the build plate. Awesome. So, I stopped the build, again. I've redesigned the model to try to mitigate this problem. We'll see I guess.

Also, I'm going to make the fins not-solid. There will be a lattice-work on the inside to save weight. Stiffness should not be a problem and they'll be plenty strong.

Don't make the mistake of putting any money into launch equipment...
Everybody makes that mistake,, including me,, I have a brand new Aerotech Mantis launch pad and controller sitting and collecting dust,,
it's been used probably twice,, I bet right now there are a hundred of them around this forum people would be willing to sell,,, join a club....


1--- The club will have far better launch equipment then you could ever hope to buy...
For your use for free.. Just join the club... Paying club dues is a far better deal then trying to buy launch equipment...

2--- There will be a wealth of knowledge at club launches,, year and years of experience ahead of where you are now...
You want to learn ?? You want to physically see all of the options you have for your upcoming project ?? Join a club....

3--- At club launches along with the years of experience go severely cool rockets and severely cool flights...
Doing it all on your own you won't see these flights for years...

4--- I have been putting up some insanely cool flights,,, as time goes by they just get better and better,, just unbelievable...
You know what the best part of my flights is ?? Doing them with all of the club there to watch and ooohhhh and aaawwww with me...
It the camaraderie,, this is priceless,, and it's free,, it comes with club membership...
Nobody loves to fly rockets more then me,, I'm sorry but flying rockets alone isn't fun...

Teddy

The engine housing and fin assembly has finally finished printing! Very happy. There's a lot of clean up work left to do, but a good start.

Looking back I should have made the part that slips into the BT longer. However, I think it'll still work.

Well, there's this for finishing:

https://www.reynoldsam.com/product/xtc-3d/ <<=== neet website for other stuff too.

It's an epoxy resin specifically for finishing 3D printed parts. How much is hype I don't know. I've used it once, and it seemed to stay tacky forever (I probably flubbed the mixing). But now I can't seem to find what I coated with it, so I don't know how it ultimately turned out. I've got some other stuff I'm going to give it a try on soon though.

Looks like you're printing PLA, so I don't know much about that. With ABS you could get some help from some acetone, and sanding is probably easier.

I've worked with ABS 3D printing parts for over 2 years now. My best results are to just sand the outer layer ridges with a 150 grit paper, then smoothing with a 220 or higher. If you can get the layers not to visually standout then a quick dip (1 second maximum) in acetone, shake the excess off and it may give a good glossy finish. After about 10 minutes, you can paint it or try smoothing it some more with the 220 paper and repeat

Caution, if your part is not solid (gaps in the material lay down, then you'll get some strange bubbles inside the wall of the plastic. If you use a lattice interior this may method not work for you.

Also, the outer millimeter of plastic literally dissolves, so don't dip it where you are handling it.

These things are handy for applying acetone in a nicely controlled manner:
https://www.amazon.com/dp/B00161O594/?tag=skimlinks_replacement-20

The mist is very fine and easy to put where you want it.

Very fine most of acetone in the air. No smoking, please!