My "first" high powered build (Binder Devistator) - advice needed

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That does look really good! One small suggestion though. If it's not too late, you may want to turn that eye bolt on your centering ring a bit. Probably won't be able to turn it much, but with it in the position in the picture, you may have a hard time getting a quick link attached.
 
That does look really good! One small suggestion though. If it's not too late, you may want to turn that eye bolt on your centering ring a bit. Probably won't be able to turn it much, but with it in the position in the picture, you may have a hard time getting a quick link attached.

D'Oh! Yeah, you make a good point, and I fear turning that is a ship that has sailed. Ohh well, going to pick up some links on my way home from work tomorrow, so I'll post back how it goes.

Got the fins epoxied to the can so they will never come off until somewhere around the heat death of the universe :). More pics in the next few days. I hope to have this done by the end of the week or next weekend. Should make it in time for LDRS. Need to get some motor hardware next!
 
D'Oh! Yeah, you make a good point, and I fear turning that is a ship that has sailed. Ohh well, going to pick up some links on my way home from work tomorrow, so I'll post back how it goes.

Got the fins epoxied to the can so they will never come off until somewhere around the heat death of the universe :). More pics in the next few days. I hope to have this done by the end of the week or next weekend. Should make it in time for LDRS. Need to get some motor hardware next!

I did the same thing once. Just hook a quick link to the eyebolt before you have everything put together. Leave it attached, and then attach the quick link from your harness to it. You will add the weight of an additional quick link, but you'll save yourself a lot of frustration when you are doing harness maintenance.
 
More work has been done. The fins are all epoxied in place so that they won't let go of the fin can until sometime around the heat death of the universe :p The fin can fit back into the body tube like a glove, super easy construction technique.

Started on the top part, got the eye bolt and center plate set in place. Also got a pair of fin stiffeners on! I am really loving this rocket, but man LDRS is coming up FAST and I need to hurry up!! I need a motor casing and to pay my range fees for the weekend! Gah, thankfully my kids rockets are all done and it is just me we are waiting on :)


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A quick question: what is the best way to protect the parachute here from the ejection charge heat? I have a bag of dog barf somewhere here in the basement, but does that scale up well enough to work on a 4" diameter body tube? Would a big handful of that do the trick or do I need something more advanced? Thanks again all!
 
Well, updating this thread kicked me to go buy a motor casing! I picked up a CTI 38mm starter set from Wildman Rocketry as well as a Nomex blanket to protect the parachute, I figure it'll be something I can reuse many times, so I solved that problem. Okay, back to work tomorrow morning!
 
Coming along nicely! It looks great! As far as chute protection, I use dog barf in my 4" rockets, but I also use a nomex blanket. Belt and suspenders
 
I use both dog barf and a nomex blanket too. Probably overkill. Dog barf should be sufficient, but you'll need to use several handfuls. You need to fill the diameter of the booster.
 
Heading into the home stretch last night and I hit a snag and have a few (probably dumb) questions I hope people can answer.

1.) (I don't even know if this matters, but...) When building up the coupler between the lower part and the payload section, the instructions say to make a mark 3" from the end of the connector tube. The connector tube is 7"... so I am not sure which end to measure 3" (or honestly, if it even matters, as I said :p). Should I measure 3" from the bulkhead side and have the bulk of the connector epoxied to the payload section, or vice versa?

2.) The connector is a TIGHT fit in the lower section tubing (I presume in the upper section too). When I dry fitted it, I had to hold the base of the rocket with my legs and use both hands to pull the coupler out. This seems... tight to me. Now, I would fully understand if I am under estimating the strength of a I-strength motor ejection charge, but I *think* that's a bit tight. I am thinking of just sanding down the coupler tube a bit until the fit is a bit smoother. Does this make sense to people?

Thanks for entertaining my stupid questions, I really appreciate all the help people have given here! :)
 
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Heading into the home stretch last night and I hit a snag and have a few (probably dumb) questions I hope people can answer.

1.) (I don't even know if this matters, but...) When building up the coupler between the lower part and the payload section, the instructions say to make a mark 3" from the end of the connector tube. The connector tube is 7"... so I am not sure which end to measure 3" (or honestly, if it even matters, as I said :p). Should I measure 3" from the bulkhead side and have the bulk of the connector epoxied to the payload section, or vice versa?

2.) The connector is a TIGHT fit in the lower section tubing (I presume in the upper section too). When I dry fitted it, I had to hold the base of the rocket with my legs and use both hands to pull the coupler out. This seems... tight to me. Now, I would fully understand if I am under estimating the strength of a I-strength motor ejection charge, but I *think* that's a bit tight. I am thinking of just sanding down the coupler tube a bit until the fit is a bit smoother. Does this make sense to people?

Thanks for entertaining my stupid questions, I really appreciate all the help people have given here! :)

#1. I also noticed that. I just measured the center of the payload bay coupler, and marked down 1/2 the height of the switch band as the stop where I would epoxy on my switch band. Not critical.
#2. I wouldn't bother sanding it looser. You don't want it to wobble around. Keep it as-is and do your ejection charge testing with 1.4g 4F BP. That's what my calculations came to when I built that rocket. I used 2 2-56 nylon shear pins as well. Separation worked well. I also used the same amount for the main chute when popping off the nose cone. It also had 2 2-56 nylon shear pins. Note: I also have steel cut plates in the tubes to help cut the pins and to prevent them from widening the holes during its lifetime.

Oops. I forgot you're building the Devastator and not the Excel. You might want to double check the charge calculations. The two look pretty similar in size.
 
Those instructions were written before we upgraded the couplers to 7" long. So you want 3.5" now. Not super critical if you are off a half inch.

On the coupler fit, the fit changes with humidity and it is the one thing that can drive you nuts so here's how to fix it. Soak the exposed section of the coupler in thin CA and sand smooth. Do the same with the inside end of the airframe you need it to slide into. You only need to soak it about an inch or two inside. Now sand both parts until you are happy with the nice sliding fit.

And no more fuzzy paper edges to worry about.
 
On the coupler fit, the fit changes with humidity and it is the one thing that can drive you nuts so here's how to fix it. Soak the exposed section of the coupler in thin CA and sand smooth. Do the same with the inside end of the airframe you need it to slide into. You only need to soak it about an inch or two inside. Now sand both parts until you are happy with the nice sliding fit.

And no more fuzzy paper edges to worry about.

I started doing this after just sanding straight up and having the cardboard de-laminate/start to fuzz. Thanks for the verification of what I am doing :) Almost there!
 
Okay, after what felt like about 18 hours of sanding :p I got the coupler to fit nicely into the booster section--tight, but not too tight. Hooray, should be able to finish the building steps tonight, then onto finishing!

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I also managed to superglue my sock to the carpet while soaking the coupler. This made me very glad I was wearing socks! :D
 
Interesting it took that much sanding. I slip fit the couplers inside the airframe prior to shipping. They slide right through with no effort needed. If they were that tight when I shipped them, you'd never get them out.
 
Interesting it took that much sanding. I slip fit the couplers inside the airframe prior to shipping. They slide right through with no effort needed. If they were that tight when I shipped them, you'd never get them out.

It was totally weird, the coupler fit into the payload section with ZERO issue. I have no idea why it gave me such fits fitting it into the booster section. But, my daughter and I finished it up last night and while naked, it looks AWESOME!!!! I will post pictures later tonight. :)
 
So after adding some Bondo, the build is done. Now onto finishing, and painting, and sanding, and painting, and sanding, and painting, and sanding, .... See how far I can get before next weekend!

This rocket looks great! I took it to work to show my coworkers and they loved it. Very impressive.

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And... all done!

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But, my daughter and I finished it up last night and while naked, it looks AWESOME!!!! I will post pictures later tonight. :)

I tend to skim read pretty quickly in forums to avoid getting bogged down in minutia, but sometimes I have to stop and read it again just to make sure it said what I thought it said. This was one of those times. :eyepop:
 
I tend to skim read pretty quickly in forums to avoid getting bogged down in minutia, but sometimes I have to stop and read it again just to make sure it said what I thought it said. This was one of those times. :eyepop:

Heh... uhh yeah that sounds very very weird... :eek:. Maybe I need to re-read before hitting post!
 
Okay, the end is in sight!!!

Spent the weekend travelling back and forth to my parents since it has been on the edge of too cold to do painting outside here. Thankfully my dad's workshop is nice and warm year round.

Two coats of white primer, then wet sanding, then two coats of maroon primer, then more wet sanding, then two coats of final gray color, then spot wet sanding, THEN a final coat of gray brings us to nearly the end!

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I really dig the aluminum nozzle, it really sets things off nicely!

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No need for glassing fins on motors up to L class. It's our standard instruction template that has to cover all the bases. And we've upgraded to the highest quality aircraft plywood since the instructions were written.

You can use wood glue for all paper/wood bonds, but the milled fiber/epoxy does make for nice fillets. With the fin stiffeners the kit comes with, extra fillet material only adds additional weight.

Just build it stock, no need to build a flying boat.

That's what I was about to say, unless you are going Mach2 and above whats the point.
 
All done!

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I reached out to Mike and he hooked me up with a rkt file to run this through the simulator. On an I power 38 mm, I am looking at easily hitting 1/2 mile and nearly 400 mph which should be awesome for a first flight! A bigger K should put this close to breaking Mach 1, which is a personal goal of mine! :D

This rocket was a blast to build, and I think it looks awesome. Big thanks to Binder Design for such a quality kit. I am eyeing a dual-deploy Velociraptor as my next high powered beast :) Now the kids and I will all have brand new rockets to bring to LDRS this weekend, I cannot wait! Thank you to everyone in here for the help when I had dumb questions! I really appreciate the knowledge you all have :)
 
Hopefully someone will read this tonight or early tomorrow. I picked up some hardware today at LDRS (a Pro38 starter kit and a I242 motor for it's first flight), after fitting it all together tonight, I realized that when fully loaded out, the CG is only ~2" in front of the reported CP (from the directions via Rocksim), this is only about 1/2 a caliper. :( I am guessing, I built too heavily in the back (I was quite liberal with the epoxy) and I want to add weight up front to move the CG up. Is there a "standard" way to do this?

I am thinking of hitting up Home Depot on my way out to the field and getting some metal weights (not sure what exactly) and 5 minute epoxy that I can secure the weight onto the bulk head at the aft end of the payload section.

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Does this make sense? Am I asking for trouble doing this? Thanks for any heads up, I make pester people at the field tomorrow to see if they have any good ideas or if I am crazy :) Thanks all!
 
Don't suppose the inside of your nosecone is accessible?

Best scenario.is if you can get them somewhere in front of a bulkhead. If there's a sporting goods store nearby, some lead shot or fishing weights are good. Or fender washers glued in a stack, other dense items etc.

If you can get them on the front of a bulkhead, you won't have to worry about the 5min breaking loose and flying backwards accidentally.
 
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