AT Cheetah Build

OC_Rocket_Man

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Hello all-

Many years ago I built an AT Initiator. Fast forward to today and my young son enjoys rockets and it's a great way to get him involved with science and math.

When I built the Initiator, I used something like HobbyLite Filler to fill in the spiral grooves on the BT. I've read people on here talking about Elmer's Carpenter's Wood Filler, but I never see a specific type mentioned and they make a slew of different formulas, tubs vs tubes etc. Is there a particular one that works better than others? Like E855, or this one: https://www.joann.com/wood-filler-1-4-pint/12752622.html How about Squadron Putty?

I'm pretty much just going to build it as instructed, with the exception of Kevlar cord going from the motor mount exiting the BT to the shock cord. I'd also like to run a Jolly Logic Chute Release and an upsized canopy if the smallish BT will accommodate this (this rocket will most likely be launched in Lucerne with winds and a hard landing area).

Thanks in advance for any advice!
 
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Hello all-

Many years ago I built an AT Initiator. Fast forward to today and my young son enjoys rockets and it's a great way to get him involved with science and math.

When I built the Initiator, I used something like HobbyLite Filler to fill in the spiral grooves on the BT. I've read people on here talking about Elmer's Carpenter's Wood Filler, but I never see a specific type mentioned and they make a slew of different formulas, tubs vs tubes etc. Is there a particular one that works better than others? Like E855, or this one: https://www.joann.com/wood-filler-1-4-pint/12752622.html How about Squadron Putty?

I'm pretty much just going to build it as instructed, with the exception of Kevlar cord going from the motor mount exiting the BT to the shock cord. I'd also like to run a Jolly Logic Chute Release and an upsized canopy if the smallish BT will accommodate this (this rocket will most likely be launched in Lucerne with winds and a hard landing area).

Thanks in advance for any advice!

This is the Elmers most use. Water it down to peanut butter consistency.

Elmers.jpg
 

OC_Rocket_Man

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This is the Elmers most use. Water it down to peanut butter consistency.

So is that colored as opposed to white? Just look for the Interior one that doesn't specify it's stainable? I saw people complaining the stainable type was like sanding a rock.
 

samb

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Elmers has a lot different packaging but the Interior orange or orange and blue tubs work. The Elmers color change has been reported to work by some TRFers. I'm sure the DAP works fine. The thing you want to avoid is anything that says "contains real wood fibers" on the package, like the Elmers stainable, MAX, or Pro labeled stuff. The Hobbylite works if you still have some.

Some tips from my favorite model rocket building blog: https://modelrocketbuilding.blogspot.ae/search?q=spiral+filling

[edit] Color. I never paid much attention to the color of the filler. Most Elmers is light tan. I never tried that white E855 stuff but it doesn't say "contains real wood fibers" so that's good. :)

[another edit] Welcome to the forum !

[hat-trick edit] Some AT Cheetah stuff here: https://www.rocketreviews.com/cheetah---aerotech-89016-1992-.html
 

OC_Rocket_Man

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Elmers has a lot different packaging but the Interior orange or orange and blue tubs work. The Elmers color change has been reported to work by some TRFers. I'm sure the DAP works fine. The thing you want to avoid is anything that says "contains real wood fibers" on the package, like the Elmers stainable, MAX, or Pro labeled stuff. The Hobbylite works if you still have some.

Some tips from my favorite model rocket building blog: https://modelrocketbuilding.blogspot.ae/search?q=spiral+filling

[edit] Color. I never paid much attention to the color of the filler. Most Elmers is light tan. I never tried that white E855 stuff but it doesn't say "contains real wood fibers" so that's good. :)

Ordered a tub of CWF from Amazon. It should arrive the same time as the Sirius Rocketry order.

Last time I filled spirals I recall using a rubber glove with the HobbyLite and just smearing it on. The razor technique outlined in your link seems more precise. This Apogee article mentioned using a toothpick. https://www.apogeerockets.com/education/downloads/Newsletter298.pdf I'll probably stick to the toothpick for the big grooves just so I don't cut the thing, and then use a more watered down version on the hidden groove.

[another edit] Welcome to the forum !

Thanks! And thanks to everyone who took the time to answer. I'm already looking at ordering more AT kits from Active Powersports.
 

samb

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OC_Rocket_Man

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Yes, and there is an addendum to the instructions showing the correct placement of the centering rings with the new retainer.

[edit] I should say check with the vendor you're buying the kit from. It's possible they might still have old stock kits with the motor hook.

It's going to be here tomorrow, so I'll just wait and see. I'm assuming Sirius Rockets turns stock over enough that they have the newish inventory.
 

soopirV

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I'm a big fan of the DAP Plastic Wood-X that they have at Home Depot:

https://www.homedepot.com/p/DAP-Plastic-Wood-X-32-oz-All-Purpose-Wood-Filler-00543/206667347

It sands just as easy as Elmer's CWF and it changes color when dry so you know when it's safe to sand. I use it on all my LPR fins and balsa cones, and to fill spirals.

I just used this after finding my CWF dried to a brick. I was hesitant since "plastic wood" had me fearful of its sandability, but it was pretty easy. my only complaint/observation was it had a fair amount of insoluble "grit" in it- making the thinning process a little less forgiving (had to err on the side of too thick, or it left streaks).
 

soopirV

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Yes, and there is an addendum to the instructions showing the correct placement of the centering rings with the new retainer.

https://www.aerotech-rocketry.com/u... Motor Retainer Upgrade Notice with guide.pdf


https://www.aerotech-rocketry.com/resources.aspx?id=4



[edit] I should say check with the vendor you're buying the kit from. It's possible they might still have old stock kits with the motor hook.

That's good to know! I stopped looking at AT kits several years ago- I have several, but they haven't had a new release in FOREVER. Glad Gary (or ever is in charge now) is still innovating. The AT kits are BEEFY, but very well designed.
 

Initiator001

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I use Elmer's Carpenters Wood Filler on all my rocket kits.

I used it on the latest Cheetah I built and flew.

AeroTech Cheetah for NARAM-54.jpg
 

OC_Rocket_Man

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Recieved my Cheetah kit today.

The good: It came with the threaded motor retainer and conformal rail guides.

The bad: The supplied 2.6" nose cone isn't going to work. Bummer, wanted to make this next week while mini-me is out of school.

The instructions are pretty weak. Like the motor retainer addendum as opposed to just having a new version. And there is no mention anywhere about the conformal rail guides.

I also got some 150# kevlar cord that I was going to attach to the eyelet off the baffle, bringing it out of the BT to attach the elastic cord to. I'm guessing I undersized this working strength now that I see it.
 

Buckeye

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Cheetah is 1.9." They put the wrong size nose cone in the kit?

You are probably fine with the 150# kevlar. The Cheetah is not very heavy. If it is thin like kite string, then keep it short so it doesn't zipper the body tube. My Cheetah has the original elastic chord attached to the baffle - going strong for many years.

Agreed on the weak instructions. What is up with Aerotech in this regard? HPR motor instructions have degenerated to one drawing full of errors, ambiguities, and addendum. Sounds like the rocket kit instructions are no better. Aerotech needs to hire a good technical writer.
 

samb

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Recieved my Cheetah kit today.

The good: It came with the threaded motor retainer and conformal rail guides.

The bad: The supplied 2.6" nose cone isn't going to work. Bummer, wanted to make this next week while mini-me is out of school.

Wow, that is a big miss for a 2 inch diameter rocket. If you haven't already, I'd get a picture of that to Sirius and Aerotech customer service.

The instructions are pretty weak. Like the motor retainer addendum as opposed to just having a new version. And there is no mention anywhere about the conformal rail guides.

I think Aerotech made a business decision to keep the original 1990's vintage instructions and go with addendums for the retainer. The instructions for my AT Barracuda were pretty basic but had no errors as I recall.

I also got some 150# kevlar cord that I was going to attach to the eyelet off the baffle, bringing it out of the BT to attach the elastic cord to. I'm guessing I undersized this working strength now that I see it.

My experience with the Barracuda is the same as Buckeye's. Stock shock cord just works.
 

OC_Rocket_Man

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Cheetah is 1.9." They put the wrong size nose cone in the kit?

You are probably fine with the 150# kevlar. The Cheetah is not very heavy. If it is thin like kite string, then keep it short so it doesn't zipper the body tube. My Cheetah has the original elastic chord attached to the baffle - going strong for many years.

Agreed on the weak instructions. What is up with Aerotech in this regard? HPR motor instructions have degenerated to one drawing full of errors, ambiguities, and addendum. Sounds like the rocket kit instructions are no better. Aerotech needs to hire a good technical writer.

Yes, wrong size nose cone included.

For a plug and play MPR the instructions are horrible. People shouldn't have to rely on forums and google for a kit of this scope.
 

samb

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Yes, wrong size nose cone included.

For a plug and play MPR the instructions are horrible. People shouldn't have to rely on forums and google for a kit of this scope.

Hmm... ok horrible is few notches above weak. I think you should definitely raise your concerns and maybe some suggestions with Aerotech customer service. That's what they're there for.
 

OC_Rocket_Man

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Can anyone guide me to some info on these conformal rail guides? Such as mounting locations? I've done searches and read through the threads, but I can't find anything telling me exactly where they go.

My assumption is they go on one of the two sides (since the Cheetah is a 3 fin design) that the launch lugs aren't on, so that you can fly on rods or rails. My assumption is also to put them in the identical position to their launch lug counterparts. But assumptions and epoxy might not work out so well for me :)
 

samb

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Can anyone guide me to some info on these conformal rail guides? Such as mounting locations? I've done searches and read through the threads, but I can't find anything telling me exactly where they go.

My assumption is they go on one of the two sides (since the Cheetah is a 3 fin design) that the launch lugs aren't on, so that you can fly on rods or rails. My assumption is also to put them in the identical position to their launch lug counterparts. But assumptions and epoxy might not work out so well for me :)

All I found were one-liners on the AT kit description pages on Sirius and Apogee, touting these new bits as features allowing more options for launching guidance. I haven't built a kit that included them so take this for what it's worth. If you don't have access to a rail launcher stick 'em in the spare parts box. Otherwise I'd place them about 120 degrees around the tube from lugs, at the same distance from forward or aft end of the airframe, however you want to look at it.
 

Rex R

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one difference between low power and mid/hpr kits* is that the person writing the instructions pretty much assumes that the builder knows the basic building techniques and so they will tell what needs doing, not how it is done. to rail or not to rail, that is the question :), do you own a rail? or do you intend to launch w/ folks that have rails? if the answer is yes then I would put the rail guides in the same corresponding location as the lugs.
*Estes is an exception with their Pro series kit instructions.
Rex
 

OC_Rocket_Man

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Through the front end of the body tube, apply cement where the baffle flange meets the inside surface of the body tube.

I'm using medium CA, so obviously I can't get my hand down the inside of the BT and it's not going to work well with a dowel or stick as an applicator.

How about a couple "tack" or "spot" welds with JB Weld applied via dowel or a straightened coat hanger?

Also, when affixing the rail guides to the BT, should I go with CA or a little JB Weld again?
 

samb

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I'm using medium CA, so obviously I can't get my hand down the inside of the BT and it's not going to work well with a dowel or stick as an applicator.

How about a couple "tack" or "spot" welds with JB Weld applied via dowel or a straightened coat hanger?

Also, when affixing the rail guides to the BT, should I go with CA or a little JB Weld again?


I'm pretty sure I used a dowel and CA when I built my Barracuda. I may have substituted a thicker viscosity at that point IDK. If you got the fins locked in good I think that the forward flange just needs a good gas seal. I think you have about 10 inches to reach that point from the forward edge of the airframe, right ? I used CA on the lugs then re-glued with 5 minute Loctite syringe epoxy when the lower lug popped off after several flights. So maybe I would just go epoxy for those guide bits from the start. The only thing I've ever used JB Weld on in a rocket is an Aeropack retainer as directed.
 

OC_Rocket_Man

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I'm pretty sure I used a dowel and CA when I built my Barracuda. I may have substituted a thicker viscosity at that point IDK. If you got the fins locked in good I think that the forward flange just needs a good gas seal. I think you have about 10 inches to reach that point from the forward edge of the airframe, right ? I used CA on the lugs then re-glued with 5 minute Loctite syringe epoxy when the lower lug popped off after several flights. So maybe I would just go epoxy for those guide bits from the start. The only thing I've ever used JB Weld on in a rocket is an Aeropack retainer as directed.

I have some JB Weld for the motor retainers. That's the reason I brought it up in particular.

And to be honest, I was thinking along terms of binding the baffle/motor tube to the body tube, not creating a gas seal (noob :) )
 

samb

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I have some JB Weld for the motor retainers. That's the reason I brought it up in particular.

And to be honest, I was thinking along terms of binding the baffle/motor tube to the body tube, not creating a gas seal (noob :) )

Ok. I think most of the binding strength on this one comes from the fin loc rings to motor tube/fin tab to motor tube/fin tab to fin loc joints. Choice of adhesive is always up to the modeler.
 

OC_Rocket_Man

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Finally got this painted today. It looks pretty nice. Rust-Oleum Gloss Apple Red BT and fins with a Gloss Black NC.

I had my old Initiator that was beat up both from its last playa landing ~12 years ago as well as being moved countless times over the years, so I decided to use it to practice techniques on. Fixed dents and gouges in the body tube as well as repaired some fin nicks with CWF and CA, sanded, primed and painted. I totally destroyed the paint with too heavy of an initial application of the color coat which crackled everywhere. At the time I was furious, then I reminded myself that the whole idea of fixing it up was to practice.

I'd post an image once it's dry but its just another Cheetah and it's ghetto looking compared to most of the builds I see on here so I'll probably refrain.

I also ordered an upsized 18" chute and some hardware from Madcow which I plan to eventually pair up with a JLCR so I can put this thing up there on G's, actually find it and have it survive it's playa encounter.

Of course now I have an AT Warthog to build, and I'm looking at a Madcow 4" kit or a LOC Magg variant to build for an L1 cert.
 

OC_Rocket_Man

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attachment.php
 

Initiator001

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Hey that's a nice stand... where'd ya get it?
Nice build and paint too.


Sent from my SAMSUNG-SM-G930A using Rocketry Forum mobile app

The stand was produced by Q-Modeling which is no longer in business. :(

Thanks for the compliment about my model.
I've built a few Cheetah models over the years and I keep building the next one better. :wink:
 
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