LOC Graduator DD build

[rockets]

Here is my build thread for my LOC Precision Graduator. I have bought extra parts so that it can be dual deploy, and I have a 38mm motor mount for it.
The other purpose that I have for this thread is that I can hopefully ask questions, as some of you may know, this is my first HPR build.
I thought about getting a wrap for it, but after watching my older brother, Kevin, making cool looking paint schemes on the computer, I figured I'd wait till my next HPR build to wrap a rocket.
So here is the info, and dimensions of the rocket:
HEIGHT 50 IN.
DIAMETER 2.63 IN.
WEIGHT I don't know yet, ??
RECOVERY
Parachute: I'm not sure yet, what do you guys think?
Shock Cord: Onebadhawk 1/8 inch kevlar cord.
GLUE 30 minute epoxy.
_________________________________________

Thanks,

 

[rockets]

LETS BUILD!
I got the 30 minute epoxy, and glued the first part of the MMT and the eyebolt.


Thanks,

 

[rockets]

So when the package arrived with my kevlar shock cord, it also had a cup holder, well, yeah, it can be used as a cup holder, but for this build it happened to be quite convenient:

And it fit PERFECTLY! great for holding a 2.56 MMT while the epoxy dries.

Thanks,

 

[rockets]

I finished gluing the other part of the MMT together, and then after that dried, I inserted it into the rocket:

I actually painted the fins before building the rocket, since they're different colors. Ted from onebadhawk also included a sticker, and I figured I'd put it to use:

I really like how it looks!
So, now I just have to insert the fins, and after that, fillet them, and then on to the Ebay!

Thanks,

 

[rockets]

I have a question:
Should I get a retainer for the MMT? If so, where can I get one?

Thanks,

 

[djs]

I have a question:
Should I get a retainer for the MMT? If so, where can I get one?

Yes, it's a good idea, although looking at your picture of the rear end of the rocket it might be too late. What's the length of the exposed motor mount tube?

I get my aeropack retainers from Wildman- www.wildmanrocketry.com , but if you don't have much exposed mmt tube, you might have to go with some screws and brackets instead?

 

[rockets]

Yes, it's a good idea, although looking at your picture of the rear end of the rocket it might be too late. What's the length of the exposed motor mount tube?

I get my aeropack retainers from Wildman- www.wildmanrocketry.com , but if you don't have much exposed mmt tube, you might have to go with some screws and brackets instead?

About a 1/4 of an inch.

Thanks,

 

[djs]

Aeropack retainers need at least 3/8" of an inch- maybe you have enough?

https://aeropack.net/webstore/product.asp?productid=6

Note- that might not be the right one for your rocket- you'd have to verify- but the 3/8" measurement should be the same.

 

[rockets]

Aeropack retainers need at least 3/8" of an inch- maybe you have enough?

https://aeropack.net/webstore/product.asp?productid=6

Note- that might not be the right one for your rocket- you'd have to verify- but the 3/8" measurement should be the same.

OK, Thanks for the info! I really appreciate it!!
Thanks,

 

[rockets]

I just hope that those thin fins hold together on some HPR motors.

Thanks,

 

[rockets]

First fin is in!
Thanks,

 

[Nytrunner]

I just hope that those thin fins hold together on some HPR motors.

Thanks,

This statement is concerning.

Describe how you're preparing the fin site and what method you're using to attach the fins.

 

[rockets]

This statement is concerning.

Describe how you're preparing the fin site and what method you're using to attach the fins.

The fins kinda seem to be a little thin. I'm using the method that my L2 brother uses, and a lot of other people use. I'd say the fins are 1/8 inch thick, not sure if I want to put anything bigger in this rocket than a I motor. What do you guys think???

Thanks,

 

[Danh]

Should be able to fly it with a Loki 38mm K at least once.

 

[Nytrunner]

The fins kinda seem to be a little thin. I'm using the method that my L2 brother uses, and a lot of other people use. I'd say the fins are 1/8 inch thick, not sure if I want to put anything bigger in this rocket than a I motor. What do you guys think???

Thanks,

1/8 plywood right? LOC uses good stuff, so the material should be tough.

Lots of L2 flyers use different methods, which is this? Internal fillets, double or triple dip, etc.... From the blurry photos, it looks like you've removed the smooth outer layer from the motor mount, so that'll help root adhesion.

Has your brother used FinSim? If he has, it could be really helpful for giving you an idea of the safe speeds these fins can fly on.
If he hasn't used it, then it'd be a good experience for both of you to learn. Of course, once you know the speed limit (hah) of the fins, you'll need to make an accurate simulations model so you can know what motors won't shred them.

If you get those things down, you'll be in an excellent position to get your TMP certification.

 

[OverTheTop]

Make sure there is no paint between the parts where you want the epoxy to bond. You don't get much strength when there is paint in the way. That is the downside of trying to paint before assembly. It can be done, but you need to mask the important areas.

 

[rockets]

Should be able to fly it with a Loki 38mm K at least once.

Yeah, that's on my checklist. Fly it on a Loki K1127. A nice fast motor will kick the Graduator HARD.

Thanks,

 

[rockets]

1/8 plywood right? LOC uses good stuff, so the material should be tough.

Lots of L2 flyers use different methods, which is this? Internal fillets, double or triple dip, etc.... From the blurry photos, it looks like you've removed the smooth outer layer from the motor mount, so that'll help root adhesion.

Has your brother used FinSim? If he has, it could be really helpful for giving you an idea of the safe speeds these fins can fly on.
If he hasn't used it, then it'd be a good experience for both of you to learn. Of course, once you know the speed limit (hah) of the fins, you'll need to make an accurate simulations model so you can know what motors won't shred them.

If you get those things down, you'll be in an excellent position to get your TMP certification.

Never heard of FinSim, will have to look into that.
Thanks,

 

[Nytrunner]

Yeah, that's on my checklist. Fly it on a Loki K1127. A nice fast motor will kick the Graduator HARD.

Thanks,

And if you want to fly it more than once, you will definitely need to reinforce the fins. I guess its never too early to learn how to glass the at end of a rocket...

 

[rockets]

And if you want to fly it more than once, you will definitely need to reinforce the fins. I guess its never too early to learn how to glass the at end of a rocket...

Yeah, that's another question I have, how much does it cost, and where do you get fiberglass sheets?

Thanks,

 

[ScrapDaddy]

Yeah, that's another question I have, how much does it cost, and where do you get fiberglass sheets?

Thanks,

This forum really seems to like soller composites for fiberglass needs (you can grab a yard of medium weight stuff for a few bucks) and you wanna grab laminating epoxy from US composites since it's way cheaper than the West Systems stuff while still being high quality. Most people use the medium cure hardener for layups.

 

[rockets]

This forum really seems to like soller composites for fiberglass needs (you can grab a yard of medium weight stuff for a few bucks) and you wanna grab laminating epoxy from US composites since it's way cheaper than the West Systems stuff while still being high quality. Most people use the medium cure hardener for layups.

OK thank you for the info!!

Thanks,

 

[rockets]

So, I attached the fins, filleted one of 3 areas on the fins, filled some of the spirals, and painted a little bit of the BT at the top.

For the fillets I used 30 minute epoxy, and some q-tips. For filling the spirals, I used Elmers wood filler, which actually worked really well. And after that dried, I sanded it down so that it would be nice and smooth. And lastly, for painting that portion of the top of the BT, I just used some cheap spray paint from HL.
So, I'm making some progress, and tonight I might show my rocket to my older brother, who is an L2. If I can get his approval, then that will be good!

Thanks,

 

[ScrapDaddy]

I'm actually not sure about this statement so I'm more asking then asserting, but I was under the impression that one should always fillet the fins before painting in more demanding situations since if you paint the fins first the epoxy will be bonding to the paint rather than the fin itself, limiting the overall bond strength to that of the paint to the wood. Also, wouldn't you want the fillets painted anyways?

 

[markkoelsch]

The fins kinda seem to be a little thin. I'm using the method that my L2 brother uses, and a lot of other people use. I'd say the fins are 1/8 inch thick, not sure if I want to put anything bigger in this rocket than a I motor. What do you guys think???

Thanks,

Flying an H motor no problem. Small I probably not an issue either. Healthy fillets are your friends.

The above has a caveat- not sure about really high thrust motors- warp nine and vmax type stuff might be a bit much.

 

[rockets]

All of the fins are in, and filleted. I have wrapped it up, and it's ready for paint.
I also got the rail buttons in.
Thanks,

 

[rockets]

Flying an H motor no problem. Small I probably not an issue either. Healthy fillets are your friends.

The above has a caveat- not sure about really high thrust motors- warp nine and vmax type stuff might be a bit much.

Probably won't fly anything bigger than a I motor. I'll talk to my mentor & my older brother and see what they think.

Thanks,

 

[rockets]

Probably won't fly anything bigger than a I motor. I'll talk to my mentor & my older brother and see what they think.

Thanks,

Although, I may look into a AT SU J270, but that would be after several H & I motor flights.

Thanks,

 

[viciouspeanut]

Have you weighed it yet now that you got everything done except finishing? Would be worth running through the thrust curve guide. A LOC Forte which is a bigger diameter than yours, but shorter since you made yours DD - sims to nearly mach on the J270 and that would likely be the end for your fins unfortunately. I motors are probably a good limit. Loki I377 would be an impressive flight.

EDIT: Just ran a sim on it assuming a 16 ounce weight and on a J270 it hits almost 1400 ft/s, well above mach. So might not want to go that route.

 

[rockets]

Have you weighed it yet now that you got everything done except finishing? Would be worth running through the thrust curve guide. A LOC Forte which is a bigger diameter than yours, but shorter since you made yours DD - sims to nearly mach on the J270 and that would likely be the end for your fins unfortunately. I motors are probably a good limit. Loki I377 would be an impressive flight.

EDIT: Just ran a sim on it assuming a 16 ounce weight and on a J270 it hits almost 1400 ft/s, well above mach. So might not want to go that route.

OK, I'm looking for a much lower thrust 38mm J motor.

Thanks,