# Aerotech strong arm.

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#### UPscaler

##### New Member
My dad has been planning to build an Aerotech strong ARM to get his L1 and L2.

yes, level 2. On a J350.

So our question here is, What upgrades should we use? Obviously the 38mm mount, eye bolt, no baffle, basically we will gut it out. something will obviously need to be done with the fins.

That's the big question, would the fins be okay with a few layers of fiberglass? Or should we cut out the templates with plywood and wrap them in glass. I suggested we at least re do the strakes, have them fit through the wall and in between the center and forward centering rings.

Sims to mach 1.15 on a J350.:jaw:

All suggestions welcome, we would like this thing to come out alive.

Do not .

#### Handeman

##### Well-Known Member
TRF Supporter
Totally agree!!!

The Aerotech kits are great for their intended purpose, which is Mid-Powered flights. With the amount of kit bashing required to make it work for L1 and L2, it would be cheaper and easier to just buy parts and scratch build something.

If you want a good L1 and L2 kit, look at the LOC EZI-65. It's a 54 mm kit so you have a huge variety of motor available. The recommeded motors range is from G to J. Build it stock and according to instructions and it will easily do the L1 and L2 for you.

If you consider the extra cost of components to make a Strong Arm work for L2, the EZI-65 would cost a lot less and be much easier to build and fly.

I would really recommend rethinking the Strong Arm for L1 or L2.

#### dixontj93060

##### Well-Known Member
I would also agree, the Strong Arm is really too small for combined L1/L2. LOC or PML have a number of good kit choices, but I feel Binder Design kits are really best for L1 as they come with the highest quality instructions and thus you will learn a lot just by going through the process of building one of their kits. If you really wanted to go with an Aerotech kit, you should step up to something bigger like a G-Force, or a Sumo. I did my L1 on a modified "Stretch Sumo" shown in the attachment.

#### cbrarick

##### Wildman CT
You could do your L1/L2 on a wildman JR. It's a easy kit to build and fiberglass as well. Practically indestructible. If you do manage to break it wildman will replace the kit, so you can try again.

rick

#### exprditer789

##### Well-Known Member
I am building the Loc Precision expediter and that is a great kit.I am using it for my level 1.You will never find the strong arm again if you use a J350 in it.Alex

#### UPscaler

##### New Member
Okay, so we have tossed the L2 idea.

However, Another idea came up, simply slide the motor block back far enough to accommodate my RT 29/240 case. So he can get his L1 on,say, an H97.

Any problems with that?

#### exprditer789

##### Well-Known Member
Still talking about the Strong Arm?

#### exprditer789

##### Well-Known Member
How much can you get the strong arm for.I saw it for about $80 but spend$20 more to get a Loc Ezi-65 or Expediter or that he could do L1 and L2 on.

##### Well-Known Member
H97J should be doable,
sims about 2500 feet with 10 sec delay.

About 12 Gees and <600 fps...

With careful building and a bit of luck
it should stick together long enough...

#### blackjack2564

##### Crazy Jim's Gone Banana's
TRF Supporter
Okay, so we have tossed the L2 idea.

However, Another idea came up, simply slide the motor block back far enough to accommodate my RT 29/240 case. So he can get his L1 on,say, an H97.

Any problems with that?

Leave the motor block out completely and the motor hook. Use a aero pac retainer or Sue's plumber's midnight motor mount contraption. She'll be back with a link.

I have flown a Arreaux on the H-97. Stock built, but using a wood screw and washer for motor retention. I did modify the payload for and altimeter and dual deploy It went 4200 ft.

But it was just done with CA and no fiberglass

This I tell you so you can have confidence that what you are trying to accomplish is very doable with just a few simple modifications

Better check with the 240 case. I think I had to get a longer motor mount tube. The baffle thats glued on the other end of Motor mount prevented the 240 case from going in all the way[ I THINK].

It's been a while since I lost it. I do remember the 180 case fit for sure. But you gotta ditch the hook or it will tear up your case.

I would replace the elastic shock cord with some nylon and use only half of the bp that comes in the 29mm high power reloads

Hobby motor come with .75 gr
High power 29's have 1.5gr
So in this small a rocket you might do some damage using all of it.

#### UPscaler

##### New Member
Leave the motor block out completely and the motor hook. Use a aero pac retainer or Sue's plumber's midnight motor mount contraption. She'll be back with a link.

I have flown a Arreaux on the H-97. Stock built, but using a wood screw and washer for motor retention. I did modify the payload for and altimeter and dual deploy It went 4200 ft.

But it was just done with CA and no fiberglass

This I tell you so you can have confidence that what you are trying to accomplish is very doable with just a few simple modifications

Better check with the 240 case. I think I had to get a longer motor mount tube. The baffle thats glued on the other end of Motor mount prevented the 240 case from going in all the way[ I THINK].

It's been a while since I lost it. I do remember the 180 case fit for sure. But you gotta ditch the hook or it will tear up your case.

I would replace the elastic shock cord with some nylon and use only half of the bp that comes in the 29mm high power reloads

Hobby motor come with .75 gr
High power 29's have 1.5gr
So in this small a rocket you might do some damage using all of it.
Okay thanks, I saw sues PVC retainer, i bought the parts to put on my project OSD. We can put one on the strong arm. Also, i believe the kit comes with a 14 inch motor tube, so with the baffle on it should be safe, I was thinking we should ditch the cooling mesh and get a nomex chute protector. I have read a few instances when the cooling mesh crapped out and rockets came in ballistic.

#### Initiator001

##### Well-Known Member
Okay thanks, I saw sues PVC retainer, i bought the parts to put on my project OSD. We can put one on the strong arm. Also, i believe the kit comes with a 14 inch motor tube, so with the baffle on it should be safe, I was thinking we should ditch the cooling mesh and get a nomex chute protector. I have read a few instances when the cooling mesh crapped out and rockets came in ballistic.
The Strong ARM has a 12" motor tube.

In twenty years of flying AeroTech kits and using the baffle design in other models I have never had a rocket come in ballistic due to problems with the baffle. Forgetting the ejection charge and a few other user errors have caused me to lose a few rockets.

#### JAL3

##### Well-Known Member
The Strong ARM has a 12" motor tube.

In twenty years of flying AeroTech kits and using the baffle design in other models I have never had a rocket come in ballistic due to problems with the baffle. Forgetting the ejection charge and a few other user errors have caused me to lose a few rockets.
A relatively new member of my club seems dedicated to building the entire Aerotech line. He is a good an careful builder. His first was the Arcas and it proved to be extremely reliable. He launches it 3 or times each outing. His next project was a G Force. It was beautifully put together but the first launch it blew the NC but the chute did not come out. It came down spinning Magnus fashion and sustained minor damage. Everyone who took a look at it, including people much more knowledgeable than me, opined that it was probably a weak ejection charge.

Todd rebuilt the G Force and and the next launch it flew beautifully but the same thing happened. It blew the NC but Magnused down. This time there was a bit more damage but he tried again with the same result. After the third post mortem, a former TRA prefect opined that he was loosing too much oomph with the labyrinth ejection system.

The rocket was repaired again but the labyrinth was replaced with a Nomex chute protector. It has worked fine every flight since. He no longer uses the labyrinths.

His latest project was a beautiful Mirage. It used a Nomex protecter and flew beautifully as well. Unfortunately it landed in a tall tree on its maiden flight. Extreme measures were needed to retrieve it and he hope to have it repaired for a Cub Scout demo this weekend.

#### C.O.B.H.C.

##### Well-Known Member
Leave the motor block out completely and the motor hook. Use a aero pac retainer or Sue's plumber's midnight motor mount contraption. She'll be back with a link.

I have flown a Arreaux on the H-97. Stock built, but using a wood screw and washer for motor retention. I did modify the payload for and altimeter and dual deploy It went 4200 ft.

But it was just done with CA and no fiberglass

This I tell you so you can have confidence that what you are trying to accomplish is very doable with just a few simple modifications

Better check with the 240 case. I think I had to get a longer motor mount tube. The baffle thats glued on the other end of Motor mount prevented the 240 case from going in all the way[ I THINK].

It's been a while since I lost it. I do remember the 180 case fit for sure. But you gotta ditch the hook or it will tear up your case.

I would replace the elastic shock cord with some nylon and use only half of the bp that comes in the 29mm high power reloads

Hobby motor come with .75 gr
High power 29's have 1.5gr
So in this small a rocket you might do some damage using all of it.

You can fit a 29/240 with the stock motor mount. I just checked on my Arreaux.

#### dave carver

##### ....what hump?
The other thing you could do with it is replace the AT mount with a 29mm tube and get rid of the baffle alltogether. If you plan on flying it a lot what happens after a while enough un-burned BP collects on the steel wool to make it the perfect source for starting a fire.

I've seen it happen twice. One was my brothers Mustang, started a two acre fire in the desert that a nearby farmer took his giant Caterpillar roadgrader out, dropped the ripper and drove around the fire, putting it out

The second burned with a smoldering fire that burned the steel wool and the plastic around it into a mass of hardening goo

This mod is nothing new or particularly difficult, I have a modified Mustang

#### UPscaler

##### New Member
A relatively new member of my club seems dedicated to building the entire Aerotech line. He is a good an careful builder. His first was the Arcas and it proved to be extremely reliable. He launches it 3 or times each outing. His next project was a G Force. It was beautifully put together but the first launch it blew the NC but the chute did not come out. It came down spinning Magnus fashion and sustained minor damage. Everyone who took a look at it, including people much more knowledgeable than me, opined that it was probably a weak ejection charge.

Todd rebuilt the G Force and and the next launch it flew beautifully but the same thing happened. It blew the NC but Magnused down. This time there was a bit more damage but he tried again with the same result. After the third post mortem, a former TRA prefect opined that he was loosing too much oomph with the labyrinth ejection system.

The rocket was repaired again but the labyrinth was replaced with a Nomex chute protector. It has worked fine every flight since. He no longer uses the labyrinths.

His latest project was a beautiful Mirage. It used a Nomex protecter and flew beautifully as well. Unfortunately it landed in a tall tree on its maiden flight. Extreme measures were needed to retrieve it and he hope to have it repaired for a Cub Scout demo this weekend.
I have heard a few times of the G-force having problems with ejection, I also hear about half a gram of 4Fg BP added to the hobby line ejection charge solves that problem.

#### UPscaler

##### New Member
H97J should be doable,
sims about 2500 feet with 10 sec delay.

About 12 Gees and <600 fps...

With careful building and a bit of luck
it should stick together long enough...
Careful building and a bit of luck is all rocketry is when you get right down to it. What happens, happens.

#### lme67

##### New Member
The Strong Arm was my first HPR kits during my return to rockerty and remains one of my favourite kits. When I did my L3, I couldn't think of a better kit to upscale.

#### dixontj93060

##### Well-Known Member
Now that's nice!

The Strong Arm was my first HPR kits during my return to rockerty and remains one of my favourite kits. When I did my L3, I couldn't think of a better kit to upscale.

#### UPscaler

##### New Member
The Strong Arm was my first HPR kits during my return to rockerty and remains one of my favourite kits. When I did my L3, I couldn't think of a better kit to upscale.
That is pretty!

That's pretty sweet too. Can you give me the specs?

#### lme67

##### New Member
This was a 2.1x upscale of the Aerotech Strong Arm using LOC 5.5" tubing, LOC 5.5L nosecone and a 75mm motor mount. The fins were custome made of 3/8 ply, glassed as were the strakes. If you're interested I can send you my L3 documentation. It's to big to be uploaded. Unfortunately, on it's maiden flight it cato'd on a CTI M1400 about 500' off the pad. I rebuilt it using the more traditional standard ARM fin configuration 6 months later and finally got my L3.

#### lme67

##### New Member
Here's the shot just before it cato'd on a CTI M1400 and the re-build using the more conventional fin configuration.

#### UPscaler

##### New Member
Here's the shot just before it cato'd on a CTI M1400 and the re-build using the more conventional fin configuration.
That really sucks.

There are many upscale projects i'd like to get to work on.

One includes the AT sumo.

I can now add this one to the list :roll:

The one that is most likely to happen soon is either a 4x or 6x alpha.

#### UPscaler

##### New Member
The other thing you could do with it is replace the AT mount with a 29mm tube and get rid of the baffle alltogether. If you plan on flying it a lot what happens after a while enough un-burned BP collects on the steel wool to make it the perfect source for starting a fire.

I've seen it happen twice. One was my brothers Mustang, started a two acre fire in the desert that a nearby farmer took his giant Caterpillar roadgrader out, dropped the ripper and drove around the fire, putting it out

The second burned with a smoldering fire that burned the steel wool and the plastic around it into a mass of hardening goo

This mod is nothing new or particularly difficult, I have a modified Mustang
Great. So that means my mustang should be coming in ballistic soon. My arcas as well?

I have no Idea how many flights they have, a friend gave them to me, I have flown each 3 or 4 times.

#### Initiator001

##### Well-Known Member
The other thing you could do with it is replace the AT mount with a 29mm tube and get rid of the baffle alltogether. If you plan on flying it a lot what happens after a while enough un-burned BP collects on the steel wool to make it the perfect source for starting a fire.

I've seen it happen twice. One was my brothers Mustang, started a two acre fire in the desert that a nearby farmer took his giant Caterpillar roadgrader out, dropped the ripper and drove around the fire, putting it out

The second burned with a smoldering fire that burned the steel wool and the plastic around it into a mass of hardening goo

This mod is nothing new or particularly difficult, I have a modified Mustang
Testing at AeroTech soon after the initial kit release showed that if ANY glue/adhesive comes in contact with the cooling mesh that it will act as a fuel and could burn.

The AeroTech kit instructions were changed to instruct the builder not to let any adhesive get inside the motor mount tube and make contact with the cooling mesh.

The black powder from the ejection charge is fully burnt, there is none left over.

#### dave carver

##### ....what hump?
Testing at AeroTech soon after the initial kit release showed that if ANY glue/adhesive comes in contact with the cooling mesh that it will act as a fuel and could burn.

The AeroTech kit instructions were changed to instruct the builder not to let any adhesive get inside the motor mount tube and make contact with the cooling mesh.

The black powder from the ejection charge is fully burnt, there is none left over.
These two that caught on fire were over 20 flights and please don't think the black powder all burns up because it doesn't and putting a nice cool steel coil where it can condence hot gasses works for a while and I'm not saying that this will happen to all but I'm sure there's more out there that never post in a forum or ever contact AT. They just move on with their torched rocket, wondering what happened

#### UPscaler

##### New Member
Just ordered the strong arm, should be here by the end of the upcoming week, which gives just a little over a week to build it and prep for the launch.

It'll happen! We can be quick and efficient.

I'll start a build thread when he gets it.

#### exprditer789

##### Well-Known Member
Just ordered the strong arm, should be here by the end of the upcoming week, which gives just a little over a week to build it and prep for the launch.

It'll happen! We can be quick and efficient.

I'll start a build thread when he gets it.

Who did you order it from?