Loc Goblin Thread

[Rocketjunkie]

Joshua, my opinion?
BSI 30 minute over the 5 minute stuff. The longer cure time gives it more time to seep into the cracks & pores & voids of the paper & wood; a stronger bond.

Building with LOC parts, even 5 minute epoxy is stronger than plywood and cardboard. The fins will break and tubes fail far before the epoxy lets go. You can even leave the glassine on but it will peel off before the epoxy fails. I peel the glassine off where the epoxy will go.
The Goblin has huge fins. You shouldn't need nose weight for any motor that will fit.

 

[Joshua F Thomas]

Everyone keeps not reading. The mass isn’t about stability. It’s about deliberately lowering at altitude for an H motor.

 

[jd2cylman]

Everyone keeps not reading. The mass isn’t about stability. It’s about deliberately lowering at altitude for an H motor.

Guilty... sorry.
I just avoid nose weight whenever possible.

 

[Joshua F Thomas]

Last of the external epoxy fillets are going down and then I'm done with epoxy.
Except, I haven't yet decided if I want to cut the nose-cone and epoxy in a bulkhead with U-bolt, for better mounting point.

Paint is all it needs after that. And rail buttons, of course.

Did any one do pre-primer finishing on the plywood fins? Or just paint them as-is?

 

[Tobor]

Did any one do pre-primer finishing on the plywood fins? Or just paint them as-is?

View attachment 429841

IIRC, I did 2 coats of Elmer's Wood Filler (Link) before spraying primer.

 

[jd2cylman]

I'm lazy. I just primered them twice and painted everything. Wood grain and spirals are the least of my finishing flaws. Once it's on a pad 200' out, it looks great....
But I'm not a huge perfect finish fan. I just wanna fly a rocket...

 

[Joshua F Thomas]

Yeah, I’m just going to primer, sand, primer. It’s to big for me to spend a ton of time on it.

 

[Nytrunner]

This is the size rocket where a handheld orbital sander pays dividends

 

[Joshua F Thomas]

This is the size rocket where a handheld orbital sander pays dividends

My wife would probably not appreciate that in our apartment...

 

[Nytrunner]

Ah, apartments do complicate matters. I was lucky to have a small outdoor balcony at mine where I ran the sanders.
(another benefit of moving in with my wife when I got married, her place has a backyard!)

 

[gtg738w]

I do ~3 coats of primer and then base coat. Did you download the sim? A small H like an H128 is not much bigger than a G. Last month my Goblin on a G80 did 482’. Not bad at all. Here is that flight and another of my NC attachment. Drill out the middle and another through the side and you can loop the cord through.

 

[Joshua F Thomas]

I do ~3 coats of primer and then base coat. Did you download the sim? A small H like an H128 is not much bigger than a G. Last month my Goblin on a G80 did 482’. Not bad at all. Here is that flight and another of my NC attachment. Drill out the middle and another through the side and you can loop the cord through.

Yeah I can't do H motors yet, no L1.

 

[Tobor]

Yeah I can't do H motors yet, no L1.

This would be a great rocket to level up with. Just say'n...

 

[Joshua F Thomas]

This would be a great rocket to level up with. Just say'n...

Oh, I know. I just need to figure out how to keep the altitude down for the launch. Another guy at my club tried to L1 cert on the exact same kit, and his drifted directly into a swampy area and has yet to be found.

 

[Tobor]

Oh, I know. I just need to figure out how to keep the altitude down for the launch. Another guy at my club tried to L1 cert on the exact same kit, and his drifted directly into a swampy area and has yet to be found.

Ouch...

 

[Joshua F Thomas]

The nosecone for this kit is a tight fit. Did anyone else sand off the protruding "rings" on the shoulder of the nosecone?

 

[ChicagoDave]

Everyone keeps not reading. The mass isn’t about stability. It’s about deliberately lowering at altitude for an H motor.

I haven't started my 4" Goblin yet - I plan on flying it at Midwest Power this year. But I did get the LOC Removeable Nose Weight System (https://locprecision.com/product/rnws/?attribute_rnws=4"+RNWS) so I could easily add different nose weights depending on the motor & flight characteristics. Once I get the Goblin built I'll try out the RWS and see how it works.

~Dave~

 

[Joshua F Thomas]

I haven't started my 4" Goblin yet - I plan on flying it at Midwest Power this year. But I did get the LOC Removeable Nose Weight System (https://locprecision.com/product/rnws/?attribute_rnws=4"+RNWS) so I could easily add different nose weights depending on the motor & flight characteristics. Once I get the Goblin built I'll try out the RWS and see how it works.

~Dave~

That's a cool piece, though I've already started modding my nose-cone. I guess you also increase the stability by using nosecone mass, but I'm not sure that's a bad thing for the Goblin.

 

[HHaase]

Oh, I know. I just need to figure out how to keep the altitude down for the launch. Another guy at my club tried to L1 cert on the exact same kit, and his drifted directly into a swampy area and has yet to be found.

Jolly Logic Chute Release. A club member borrowed mine for his L1 with a Sirius Eradicator, which also suffers from the same issues of long distance recovery.

This thread has been awesome to follow. I told the Wife that I want a 7.5" Goblin for Christmas/Birthday, and was very clear it's at the top of the list.

-Hans

 

[Joshua F Thomas]

Jolly Logic Chute Release. A club member borrowed mine for his L1 with a Sirius Eradicator, which also suffers from the same issues of long distance recovery.

This thread has been awesome to follow. I told the Wife that I want a 7.5" Goblin for Christmas/Birthday, and was very clear it's at the top of the list.

-Hans

Maybe I should borrow one, I don't feel like putting out $130 for one right now....

 

[jd2cylman]

Maybe I should borrow one, I don't feel like putting out $130 for one right now....

That and a sonic locator beacon of some sort. Some people figure out a way to use those personal sound alarms. Just use something to help you find it.

 

[Joshua F Thomas]

I do in fact have a sonic beacon, which I’ll use for sure.

Still trying to find out if anyone else had to “shave” down their nose cone shoulder to make it fit better

 

[jd2cylman]

I don't recall having to sand the shoulder at all. But I'm sure it could be needed. The tubes may vary a fuzz, or the cone might have swelled after it came out of the mold... Just remember, a little snug is better than too loose. Ya wanna be able to pick up the rocket by the nose, then give it a shake and it should fall off.

 

[Joshua F Thomas]

My nosecone is so tight I have to press down *hard* to get it to fit into the body.

 

[jd2cylman]

Well, that's not good... Sand it down... You can always shim tight with tape...

 

[Joshua F Thomas]

I finished modding my nosecone. It’s set up for an later e-bay. Right now it just has the retaining ring epoxied in, and the bulkhead which screws into that.

 

[gtg738w]

Still trying to find out if anyone else had to “shave” down their nose cone shoulder to make it fit better

Yes, you will need to sand to fit. As said above, sand it down until you can pick it up by nose cone but still shake it loose.

Are you planning to fly on the 19th?

 

[Joshua F Thomas]

Yes, you will need to sand to fit. As said above, sand it down until you can pick it up by nose cone but still shake it loose.

Are you planning to fly on the 19th?

Hi Russ,

Yeah, I'm hoping to fly on the 19th. All I have left is paint and decals. Need to assemble those G motors I bought from you.

Edit: ... and rail buttons. It would be a very bad thing if I forgot to install those...

 

[Joshua F Thomas]

So who is using the motor-mount adaptors that come with the kit?

I attached the 29mm adaptor to test the fit. After removing it later, I noticed that one of the t-press nuts had come off the aft retaining ring. Apparently if you screw down the adaptor enough, you will start to force the t-press nut to lift from the retaining ring.

I hammered it back in, and used some epoxy inside the hole where the threaded insert goes. I am a little concerned that either a) I will over tighten the adaptor again and cause the engine mount to fail, or b) not tighten the adaptor enough in order to avoid situation "a", and the adaptor will work itself loose, also causing engine failure.

Thoughts?

And no, I no longer have the space available on the rear to use a different engine retainer. I would have to rip out the entire aft centering ring.

 

[dr wogz]

So who is using the motor-mount adaptors that come with the kit?

I attached the 29mm adaptor to test the fit. After removing it later, I noticed that one of the t-press nuts had come off the aft retaining ring. Apparently if you screw down the adaptor enough, you will start to force the t-press nut to lift from the retaining ring.

I hammered it back in, and used some epoxy inside the hole where the threaded insert goes. I am a little concerned that either a) I will over tighten the adaptor again and cause the engine mount to fail, or b) not tighten the adaptor enough in order to avoid situation "a", and the adaptor will work itself loose, also causing engine failure.

Thoughts?

And no, I no longer have the space available on the rear to use a different engine retainer. I would have to rip out the entire aft centering ring.

I ditched the included adapters..

And, uh, I think you put the T nuts in backwards if you are pulling them out by tightening them. The T nuts should be on the inside of the CR / fin can assembly. Tightening the adapter in place should pull everything together.. the T nuts are design to be loaded under tension, and the prongs are really just to hold them in place & stop them turning.. The holding forced comes from the flange of the T nut pressing against the other side of the wood member you are tightening against. The flange of the T nut acts like a washer & nut assembly..

The 1st illustration was stolen of a site for installing some boot thing. but the principles are the same..
The 2nd illustration shows how the pieces are held with a screw & T nut. Note the orientation of the screw & T nut..