4" LOC Goblin...

Just want to drop a line and say this is hands down the best HPR kit I have ever built.

That is all.

dont do this....

roytyson said:

dont do this....

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What happened there?

not sure, except the motor deploy did not go off. I suspect I got grease on the delay, as it was burned, but the BP did not ignite. I got a new forward closure, and I was not convinced it was right, so I had the dealy in and out about three times making sure it was correct. I think I must have got grease on it.

I cried....

I can vouch that getting even a small amount of grease in an Aerotech forward closure aperture will prevent ejection. You get a clump of greasy BP in there that will not burn. I've heard Gary Rosenfield say more than once that grease strongly inhibits the face of the delay grain too and can prevent the delay from igniting during the propellant burn.

Also, too much grease on the walls of the delay grain well will be pumped into the touch hole leading to the ejection charge and prevent ignition of the charge.

Right. Grease on delays sucks rocks.

Back to topic...LOC's 4" Goblic is awesome

DAllen said:

Right. Grease on delays sucks rocks.

Back to topic...LOC's 4" Goblic is awesome

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It's my winter build.

Pictures!! Been thinking about doing one of these.

caveduck said:

Pictures!! Been thinking about doing one of these.

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Sorry. No pictures of the build.

Stop thinking about it and buy the daggum thing.

You haven't seen my build pile already...

That being said, it was the best build I have ever done. I only got two flights but had (and still have) great things planned for that rocket. I will certainly get another one at some point. The motor mount design is the most versatile rocket on the market for any level. My Purple Goblin will rise again!

roytyson said:

That being said, it was the best build I have ever done. I only got two flights but had (and still have) great things planned for that rocket. I will certainly get another one at some point. The motor mount design is the most versatile rocket on the market for any level. My Purple Goblin will rise again!

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Agreed. First flight planned for me is a Loki I405 with a chute release. Should be a nice little kick in the pants but I am sure it can take it.

DAllen said:

Agreed. First flight planned for me is a Loki I405 with a chute release. Should be a nice little kick in the pants but I am sure it can take it.

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Flown 'em on an F50-4T, flown 'em on a K535W! Versatile bird; you'll like it, Dave!

I like mine also. It's flown on a wide range of motors so far. From a AT I245G to a AT K456DM. My main go to motor case for this rocket though is the AT 54/426 motor. Great for lob shots at "Da Bong".

Flew this bird twice this past weekend. Once on a H283ST and once on a H242. Even though some idiot forgot to turn the chute release on the first flight it managed no damage whatsoever. The second flight on the H242 the chute release was ON and it was about as perfect a flight as you can get. I have a I140 I may have to stuff in it next time so long as it isn't too cloudy like it was yesterday.

So to explain the lettering on the side that says "Joe Roc 3620" that is a reference to my kids robotics team. They are the "Average Joes" and the team number is 3620. Every year they name their robot "Joe Bot." I thought it only fitting to name it "Joe Bot 3620" after painting it in the school colors.

Here's mine, on an I245 Green!

I picked up a LOC Goblin at eRockets for $80 on their most recent sale.
It should look great next to my LOC IV that I got at the eRockets Black Friday for $60, and I also got a LOC IV for my SS recipient as well.
Too many great deals in the past couple of months that just couldn't be passed..



Thanks,

dr wogz said:

Here's mine, on an I245 Green!

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Does it have that trick tab locking fin can? I want to build one of their rockets that has that.

You referring to LOC 'N' Fin? Pretty sure they stopped using that and now it's regular TTW construction on all kits.

viciouspeanut said:

You referring to LOC 'N' Fin? Pretty sure they stopped using that and now it's regular TTW construction on all kits.

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I see. Didn't know they stopped doing that. I thought it was a pretty cool idea but I bet it costs more to produce.

My 3" Iris was just regular TTW.

Tyler P said:

Does it have that trick tab locking fin can? I want to build one of their rockets that has that.

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Yes, but I left out their multi-motor adapter and went with a 54mm retainer and i use a 54-38mm adapter. Cleaner look n feel. And I built it a la traditional method: CRs on the mmt, at the right place, then slid that in, added fine, then added the rear CR.

Oh, and it's all with yellow wood glue and a bit of epoxy..

Note that the new thing is tabs locking into the CRs, not the old tabs at the bodytube.

dhbarr said:

Note that the new thing is tabs locking into the CRs, not the old tabs at the bodytube.

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That's what I thought! That system looks very cool, and strong!

My initial issue I had with the "build outside then slip it into the tube" build, was, that if the two CRs aren't perfectly aliened you end up with 4 misaligned fins and a fin can that won't slide nicely into the precut slots in the tube. I don't' remember reading anything in the instructions about how to ensure alignment. (Then again, I did just skim thru them..)

To me, when I built mine, the tabs into the CRs method just seemed to:

• Ensure a greater chance of misaligned fins
• Ensure a greater chance the fins won't align with their slots
• Requires a tighter tolerance between parts
• Weakened the CRs
• Made it hard to get internal filets (against the inside of the tube)
• Made it had to get a proper surface to surface glue bond (Too many surfaces that slid together, rather than being pressed together)

dr wogz said:

My initial issue I had with the "build outside then slip it into the tube" build, was, that if the two CRs aren't perfectly aliened you end up with 4 misaligned fins and a fin can that won't slide nicely into the precut slots in the tube. I don't' remember reading anything in the instructions about how to ensure alignment. (Then again, I did just skim thru them..)

To me, when I built mine, the tabs into the CRs method just seemed to:

• Ensure a greater chance of misaligned fins
• Ensure a greater chance the fins won't align with their slots
• Requires a tighter tolerance between parts
• Weakened the CRs
• Made it hard to get internal filets (against the inside of the tube)
• Made it had to get a proper surface to surface glue bond (Too many surfaces that slid together, rather than being pressed together)

Click to expand...

Draw a line on the motor tube for fine alignment. When you install the CRs put a fin in place along the line to ensure that the CRs are aligned properly.

I assembled mine outside the BT. This allowed strong fillets on both sides in the CRs to motor tube and fin root to motor tube. After putting the motor tube in the BT you can get a good fillet on the top of the top CR and both sides of the bottom CR with a little creative gluing. Then you fillet the fin to the outside of the BT. You're really only missing the fillet on the inside of the BT to fin. I feel like the strength of the assembly and the increased assurance that I have good MMT fillets makes up for the ones I'm missing.

Flown mine on a J and it feels rock solid.

Rainmaker said:

Draw a line on the motor tube for fine alignment. When you install the CRs put a fin in place along the line to ensure that the CRs are aligned properly.

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I agree with the line, and they could have gone a step further with the their laser and etched a line from the tab slots to the center circle cut-out to help align the tab slots on the line. And that's assuming you drew a straight line!

But to me, it just seemed like an additional step to potentially get things wrong when gluing up the CRs and maintain their alignment. You can also run the risk of having one or both CRs misaligned / not parallel to each other, causing one fin to have a gap, and the opposite fin to have an interference.

I did my usual thing, glue the forward CR (of the fin can) to the MMT. Then I glued this all in the BT, aligning the tab slots of the forward CR with the slots in the BT so that the fin tab would drop into its slot. I then placed the rear CR in place while the glue dries. Once cured, I then added all my fins. The forward fin tab fitted into the slot on the CR, and it all glued itself nicely. Wipe up any drips & dribbles, and ensure the rear tab (for the rear CR slot) was clean. I then returned the rear CR loosely in place to keep it all aliened. And again, once cured, and removed the rear CR, I then made my usual internal fillets. Finally, I affixed the rear CR. The rear CR, at this point, is free to rotate and align itself to the fin, not the fin to the CR.

My thinking was, that I am doing the assembly in the tube, not outside. I can use / rely on the BT slots help ensure the fine are aliened because they are the guide. And I get a chance to add fillets as I need, to all but the rear CR surface (a rather short section.) The tab-in-CR parts all align, and you're building it while the fins are in the slots, so you don't have to worry that they're mis-aligned. And, you dont' have to cut the end of eth tube, which I find allows the tube to flatten out / no longer be round/ And, I could have added foam before closing it all up with rear CR. I could also use a typical fin alignment guide to ensure the fins are perpendicular. I found the tab slots tight, and a little bit of sanding could cause them to vary one way or the other.. And you are relying solely on the tabs & slots to ensure the fins are perpendicular.

I achieved the same result, with an extra fin fillet (inside the BT) and I ensured the fins were in their intended slots when the glue cured.

I glued the aft centering ring on first then glued a single fin with the help of a triangle. Once set, I glued the opposite fin on clamped to the first with a angle stock. Then I fitted the second centering ring without glue to help fix the third fin. Once set, I glued the fourth clamped to its opposite like the first two. Lastly, I pulled the second centering ring off so I could glue it back on. All square and VERY solid. All glued up with Titebond. The whole process took about an hour.

I built my fincan outside the body tube. Made for a very strong assembly. Used a square to align the fins and centering rings. The fun part was spreading the body tube to get the unit in by myself... I just cut slits so the gaps wouldn't be noticeable. All yellow glue. No need to use a glue fillet on the joint between the fins and inside the body tube.