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  #1  
Old 09-25-2007, 08:44 AM
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NavyChief NavyChief is offline
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Default Estes to Aerotech Conversion

When I last left model rocket world, the RMS technology was just coming into the spotlight (1982/3). I joined the Navy back then to go play with the real things. Well, atleast the targeting/navigation equipment controlling them.

Ok, I have built several Estes rockets and grown bored of them. I feel the need to "Kick it up a notch.". I am currently working on a Estes X-Prize Canadian Arrow and a Prowler that I could like to convert to use the Aerotech motors. Since I am in the building process now, it would make since to effect these changes now instead of tearing the model apart to change the motor mount over to aerotech ability??? What do I need to do to the motor mount to be able to use the aerotech motors??? Estes thrust ring and motor clip????

respectfully,
Anthony Jackman
US Navy Senior Chief Petty Officer (ret)
SI International
eLearning Application Developer
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  #2  
Old 09-25-2007, 09:03 AM
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chanstevens chanstevens is offline
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OK, a few basic guidelines which apply MOST of the time...

You can generally stick with same motor tubes as Estes uses, maening you don't need to swap out a BT-20 for a BT-50 , though you'll find over the long haul (10+ flights) that thin wall tubing, in general, might not hold up as well to the AP heat as thick wall or foil-lined tubing. If you want a more rugged motor tube, then thicker wall substitution is in order, which then means you have to also pick up different centering rings.

It's possible to still make use of the Estes hooks in 18mm and 24mm models, though I usually avoid them. If you do use them, you typically need to break off the forward tip, since it will catch on the powder cap of a reload case (I pack mine differently and don't use this cap). Most of us just use tape/friction for retention instead of the hooks. The main advantage of losing the hooks is that you can go with longer motors. You mentioned Aerotech specifically, which are generally no longer than the Estes equivalents in 18 and 24mm, but Ellis makes some interesting motors in 24mm that are quite a bit longer than Estes, as does Apogee.

I'd also, at least initially, make sure you maintain same motor diameter. Many of us here subscribe to the theory of "you can never be overpowered" and will do insane stuff like put a 29mm tube in that Canadian Arrow to fly it on a G or H for scale-like altitudes, but that seriously affects the stability of the model and needs other adjustments like nose weight. If you stay at the same motor diameter, most of the time you will not be drastically changing the CG enough to go unstable (though that Canadian Arrow IS pretty marginal to begin with).

I'd also suggest you take a peek at Semroc.com. They offer a number of mid-power kits (check out the SLS line) that are rugged and many have versatile motor mounts/adaptors that allow you to fly a wide range of motors, and baffle systems to take most of that ejection charge so you don't go through bushels of wadding (assuming you haven't caught on to dog barf yet).
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Old 09-25-2007, 10:59 AM
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CPMcGraw CPMcGraw is offline
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Anthony,

I see you found us. Welcome to YORF! You've already been "warned" about this being an asylum. Case in point -- 29mm motors in a Canadian Arrow...

Hope the reply I sent concerning the Vindicator didn't discourage you about tackling the project...
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Old 09-25-2007, 11:16 AM
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Default P.s.

One other thing to consider that I forgot to mention--as you go for higher thrusts than the kit was originally designed for, you might also have to look at some of the key structural aspects--cardboard centering rings, 1/16" balsa fins, fillets, etc. Material-wise, fins are about the only thing I've typically seen fail, and I've even used cardboard from a cereal box for centering rings on a G80, but you'll really have to learn about glue options for this stuff to hold up.

Example--yellow/wood glue works fine on centering ring bonds and attaching fins, but much more than an F12 and you would not want to use it as a fillet, and a cardboard centering ring will stretch or tear. For fillets, switch to thin epoxy (at least 30-60 minute cure stuff at hobby shops). For centering rings, go with something like Elmer's Probond or Gorilla glue, which will expand when you sprinkle a little water on them. They wind up forming another strong/lightweight centering ring...

Fins might need to be upgraded to basswood or thicker balsa, or reinforced with a laminate of dilluted white glue and a layer of paper.

That Estes tri-fold paper shock cord mount and rubber or elastic also has to go, even if you stick with low power. Most of us upgrade to Kevlar cord, anchored to the motor mount. Kevlar is available at a number of online suppliers like asp-rocketry, balsamachining.com, Pratt hobbies, etc. You'll find those AP motors tend to have much stronger ejection charges, as they're designed to work in larger diameter/longer tubes with more volume of air to move.
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Old 09-25-2007, 07:54 PM
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Thumbs up Estes to Aerotech conversion

Thanks guys for the suggested input. It is very helpful.

I do not intend to change the motor diameter just yet. That way I have just one variable to see change vice several others. Blame it on being a cryptologic and avionics technician in the US Navy for 23 years. KISS while experimenting. I just want to experiment with different motors/manufacturers while keeping as much the same as possible. I think I will change the centering rings and motor mount to accommodate the increased heat production of AP motors. For the time being, I will just use the friction fit system to keep the rocket from backing out during recovery ejection phase.

I already tissue and CA reinforce fins on my models of 1.5 inches diameter and bigger.

I am trying to work my way up to high power. But I have to understand new modeling techniques before I make that jump.

Craig,

I have not put away the idea of building that BARCLONE rocket. Wife said I have to build the rockets that I have in kit form before jumping to anything new.


Tony


respectfully,
Anthony Jackman
US Navy Senior Chief Petty Officer (ret)
SI International
eLearning Application Developer


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  #6  
Old 09-25-2007, 08:53 PM
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You need to start training the wife right away. We wear our build queues like badges of honor, and you should never consider it acceptable to clean out the backlog before moving on to the next thing. Every time my wife starts commenting on another box showing up, I just remind her it's cheaper than a mistress/divorce.
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  #7  
Old 09-26-2007, 12:49 AM
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Quote:
Originally Posted by NavyChief
...I do not intend to change the motor diameter just yet. That way I have just one variable to see change vice several others...


Hmmnnnn...

You're still thinking rationally, Anthony. That's not a good sign. You're supposed to be sick, so start acting that way! Can't have rational thinkers on this forum; people might take notice...
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  #8  
Old 09-26-2007, 08:47 AM
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Red face Rational Thinking

Sorry guys for the rational thinking. Blame it on two divorces, 24 years in the US Navy (enlisted/retired) and a BS in Physics. I will get there where you guys are, just takes me a little longer.

Tony
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  #9  
Old 09-26-2007, 12:41 PM
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Cool Re: Rational Thinking...

Isn't all it's cracked up to be... Pun intended!

Don't worry, Tony, it won't take long before you become as rocket-crazed as the rest of us around here...

Looking at the plastic bottles in the recycled bin and thinking 'That might be a good looking rocket.'

Every time you see a write-up on a new kit thinking 'Gotta get one of those!'

And, of course, picking up the "more power!" refrain for every kit you assemble. So many Estes kits in my collection with 'D' engine mounts instead of the wimpy 18mm mounts, I was thinking about getting my 'D's in caselot quantities! Now with the rather slow moving 'E's available, I have to look at the CGs with that extra 1" of motor hanging out the tail, taped in place...

You Will Enjoy it ! But logic is not required to enjoy the ride !!!
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  #10  
Old 10-11-2007, 11:05 PM
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I recommend that you get a kit specifically designed for Aerotech motors to see how these kits differ from an Estes kit. After that you can decide if you want to buy more kits or design your own stuff.

Chanstevens recommends checking out the SLS line at Semroc, I second that. To be honest I have never bought an SLS kit from Semroc, but I have bought plenty of parts from Semroc and it has all been top notch stuff.

Or you could get an Aerotech kit. A friend just built an Aerotech Initiator and he was very impressed.

Last edited by Zeus-cat : 10-11-2007 at 11:26 PM.
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