[Motor Purchased] 5 inch diameter rocket and a CTI O3400.

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I didnt realise these could be put on a big breather hose - Now i just need to go find/make some fittings so I can do this too!

Looking good there Andrew, keep up the good work.
 
Well now its just finishing. I have the upper transition piece finsihed. So where CF meets the airframe forward of the fins is nicely smooth and level. Now its on to put some thin layers of epoxy down so that I can begin to do some wet sanding beginning with 400 grit.
 
Its been a while. I did 3 coats of epoxy on the fin can. Then wet sanded with 400 grit. There are still some low spots. I am gonna do a few more layers then resand with 400 grit.
 
I have a BRB900 I have used no issues. For this project I am using that. But for back up if I use my buddies Walston radio tracker is there any chance they can interfere with each other?
 
I don't see how they could, one is the 216-219 mhz and the other on the 900-925mhz frequency. I have flown a Eggfinder and a Marshall transmitter next to each other with no problems. What is the range of the BRB900? I can't find that info on their website.
 
jus_rockets said:
I don't see how they could, one is the 216-219 mhz and the other on the 900-925mhz frequency. I have flown a Eggfinder and a Marshall transmitter next to each other with no problems. What is the range of the BRB900? I can't find that info on their website.
Click to expand...

Range is approx 6 miles using the included antennas, up to 15 miles using higher gain (Yagi) antennas for the receiver.
 
After sanding the fin can after 3 layers it still had some low spots. So I took a different approach. Rather than using foam brushes to brush on thin layers of epoxy. I took mircofiber towels and cut them up in thirds. I dipped the towel is epoxy and wipe the fin can down with epoxy. I have found that this is a way to control the amount of epoxy better. There is less streaks. I have done 2 layers like this I am gonna do one more layer then sand again with 400 grit. Hoping that I got the low spots filled.
 
andrewlathrop87 said:
After sanding the fin can after 3 layers it still had some low spots. So I took a different approach. Rather than using foam brushes to brush on thin layers of epoxy. I took mircofiber towels and cut them up in thirds. I dipped the towel is epoxy and wipe the fin can down with epoxy. I have found that this is a way to control the amount of epoxy better. There is less streaks. I have done 2 layers like this I am gonna do one more layer then sand again with 400 grit. Hoping that I got the low spots filled.
Click to expand...

This sounds a lot like the process I use. After dry sanding, I wipe on a coat of epoxy, but then I remove most of it. I do this twice. This doesn't fill any low spots, but it does fill any scratches in the finish faster than wet sanding. After those coats, I wet sand one last time using a sponge to hold the paper (so that any low spots get sanded too). Finally, one last wipe of epoxy for shine (again, removing most all of it). I've found that this can give a fine result. I've also found that trying to build up low spots with epoxy can be difficult, particularly if your base fin surface is fully cured.

Jim
 
This sounds a lot like the process I use. After dry sanding, I wipe on a coat of epoxy, but then I remove most of it. I do this twice. This doesn't fill any low spots, but it does fill any scratches in the finish faster than wet sanding. After those coats, I wet sand one last time using a sponge to hold the paper (so that any low spots get sanded too). Finally, one last wipe of epoxy for shine (again, removing most all of it). I've found that this can give a fine result. I've also found that trying to build up low spots with epoxy can be difficult, particularly if your base fin surface is fully cured.

Jim
Click to expand...

Hey Jim I am afraid to dry sand. Will it not scar it up to bad? I have been sanding with 400 grit. I do have some wett/dry 200 grit paper. I have 2 thin layers on that I wiped on. You can see some streaks. There are areas where its pretty good and some areas where there was a little to much epoxy that ran a little bit. What is ur advice for me going further?
 
andrewlathrop87 said:
Hey Jim I am afraid to dry sand. Will it not scar it up to bad? I have been sanding with 400 grit. I do have some wett/dry 200 grit paper. I have 2 thin layers on that I wiped on. You can see some streaks. There are areas where its pretty good and some areas where there was a little to much epoxy that ran a little bit. What is ur advice for me going further?
Click to expand...

The approach that I first tried with carbon parts started with painting the initial carbon surface with 6 layers of epoxy and then trying to sand this to a smooth finish. I'd start with 120 or 180 and try to get to 320 dry. Then, I'd switch to 400 wet and go to 600 or 1000. The problem that I experienced with that technique is that the amount of sanding required to remove the stratches from the initial dry sanding usually resulted in sanding "into the carbon" at some point. The shortcut that I published a while back was to wipe the surface with a couple of coats of epoxy between the dry and wet sanding steps. The idea was to wipe off as much of this epoxy as possible - to the point where it felt dry, and where the cloth I was using didn't "drag" on the surface due to wet epoxy. What I found was this process still left enough epoxy on the surface to fill the scratches from the dry sanding. I'd do this twice, and the result was much less sanding overall and less sanding into the carbon. With a fair amount of wet sanding, it was possible to get a mirror finish. Today, I would shorten the process even further by wet sanding with 400 and maybe a few passes with 600, and then wiping on and removing one final coat of epoxy. The trick with this approach is that you really do need to wipe off all of the epoxy, or you'll get the streaks you noted.

So, what you should do depends on what you did to get where you are. If you didn't build up an epoxy layer to sand into (my six coats), then you can't do much more sanding. I'd probably wet sand at 400 as needed to remove the streaks (might take longer than you think), and then wipe on several layers of epoxy, completely removing each layer. By the second or third pass (wet sanding a bit between coats but not after the final coat), you should have a reasonable finish.

Jim
 
Well I have gone ahead and sanded the fin can up to 2000 grit. I plan on sanding up to 3000 grit. At that point I will tape off any areas of low or high spots that i have missed. For the most part it is getting there to being glass smooth. I have seen different techniques. After I done with 3000 grit go ahead and clearcoat it then polish it up with automotive polish. Or wipe on/wipe of epoxy.
 
Any thoughts of taking my rocket to a auto body shop and have a professional clear coat applied? I have called a few in my town. Most have said 50 buck or so.
 
IDK? I assume its the same stuff like the clear coat you can buy in the spray can at the local autoparts store. I have used dupli-color brand clear coat and its nice. I just thought it would look nicer with an automotive grade clear coat. But other than that I have never seen any high temp clear coat. As far as I am concerned the clear coat adds cosmetic look, does not add structure. If it burns or peels off after flight I can sand it down and redue it. Saying that I am gonna put high temp epoxy on the tips of the fins.
 
Well folks i am picking my rocket up tomorrow morning from the body shop. I took it there to get a automotive grade clearcoat. They told me it looks cool! Hope it is lol!
 
andrewlathrop87 said:
Well folks i am picking my rocket up tomorrow morning from the body shop. I took it there to get a automotive grade clearcoat. They told me it looks cool! Hope it is lol!
Click to expand...

I can't recall ever seeing a professional clear coat over carbon. Can't wait to see how it turned out.

Jim
 

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