54mm Minimum Diameter (build/designing)

[AndersLT]

Hello!


I'm currently under the phase of designing and building a 54mm MD rocket I say this because I have most of the parts but I am still optimizing most areas. First you should know that I'm using an ACME fin can that I will mod to a more aerodynamic shape. Secondly you should know that this rocket is buillt to fly a 4 grain Pro54 motor max this is because 5+Grains are out of my price range but I do plan to fly 5+ grains in the future. Thirdly the rocket air frame is is 100% fiber glass (Proline 54mm from the rocketry warehouse). Sorry no pictures yet I can't start building until the 19th of December due to me being in another city but I will post more as soon as I can. I was too exited and i was so exited to post about this a little early. :blush:


Here is some other information:


Motor Retention: Aerotech MD retainer (bolded not glued into air frame)


Motor: Cesseroni pro 54mm 4 grain with tapered rear closure


Fins: Modded ACME fin can


Recovery: 24 inch parachute, ten feet of Kevlar split in 2, drogue less DD main at 1200 feet


Electronics: Adept 22 (unsure tracker)


Length: 123 cm


Weight (dry): 1435 grams


OR file:View attachment 54mm Md rocket TRF.ork


Speed: Mach 1.66 (OR)


Altitude: 12,081 feet (OR)


Stability: 2.0-1.75 cal through out flight (OR)




Questions:


1. How can I improve the rocket?


2. Have you ever trimmed/modded a ACME fin can?


3. Optimization

Anders :wink:

 

[mpitfield]

I would go with a longer recovery harness, ideally 20' but 15' min. That being said you may find once you have your deployment charge and attachment points for your recovery harness in the drogue section that the approx 1.75" will be tight. I have roughly 6" in my 54mm MD but it is not drogue-less, I use a 12" drogue with a 20" 11/32 One Bad Hawk Kevlar 3 loop harness, which is sewn into the eye-bolt on top of the Aeropack and single 1/8 stainless quick link. All of that plus dual small blast caps for the ejection charge makes for a tight fit, so much so that it is about 1/8 apart and I have to use the shear-pins to keep the sections together. Extending the booster section may be your best choice as it will also provide you the additional motor choices you may want down the road. It is a reasonable change and you may find that having the option is nice.

As for the Acme fincan. I have one in my parts box and haven't had a build for it yet but from what I have seen they are really tough. The only thing I have done to mine is clean up the edges and holes in the middle as there was a bit of excess material left over from the casting.

 

[AndersLT]

I would go with a longer recovery harness, ideally 20' but 15' min. That being said you may find once you have your deployment charge and attachment points for your recovery harness in the drogue section that the approx 1.75" will be tight. I have roughly 6" in my 54mm MD but it is not drogue-less, I use a 12" drogue with a 20" 11/32 One Bad Hawk Kevlar 3 loop harness, which is sewn into the eye-bolt on top of the Aeropack and single 1/8 stainless quick link. All of that plus dual small blast caps for the ejection charge makes for a tight fit, so much so that it is about 1/8 apart and I have to use the shear-pins to keep the sections together. Extending the booster section may be your best choice as it will also provide you the additional motor choices you may want down the road. It is a reasonable change and you may find that having the option is nice.

As for the Acme fincan. I have one in my parts box and haven't had a build for it yet but from what I have seen they are really tough. The only thing I have done to mine is clean up the edges and holes in the middle as there was a bit of excess material left over from the casting.

The plan is to use shear pins. I'm choosing not to lengthen the booster section because all I really want to fly is a 4 grain because I will make an all carbon rocket for larger motors. About lengthening the drogue section I will have it slightly longer as for it is drogue less so all I really need is to fit some tubular Kevlar in. As for the recovery harness I probably should lengthen it not sure how much yet.

Thanks for the response

 

[AndersLT]

Last of the parts where ordered this afternoon!

Well kinda I still need a tracker...



I'm so excited for this build!

Couple more questions

1. Is the Adept 22 Mach safe? If not I'm still looking at different altimeters


2. Any cheap trackers you would recommend?


Anders

 

[DizWolf]

You're already using an acme can....why not just use a regular aeropack? much easier, especially with CTI motors.

 

[AndersLT]

You're already using an acme can....why not just use a regular aeropack? much easier, especially with CTI motors.

True I was considering using a slim line but I ended up using the area pack MD.


I'm also using the taper aft closure.


Thanks for responding

 

[grouch]

I'd still use the Slimline so there will be no issues with case length of you ever wanted to go larger.

 

[patelldp]

I personally love the ACME fin cans. They're aerodynamically awful and heavy as hell, but the fins are perfectly aligned and they're simple to install. You won't come close to breaking any records with them but they're simple, strong, and contribute to a rocket that flies nicely.

I have a 54mm fin can on my "Old School Cool" rocket that has flown a bunch of times in Cobleskill, NY on 38mm and 54mm I motors. The tubes and cone are FWFG and I used an AeroPack threaded motor retainer. The resulting rocket will go pretty high for the East Coast of the US on larger 54mm motors, but stays close to home (1,900') on the 54/1G motors. I attach the shock cord to the fore bulkhead of my motors.

There's a 38mm fin can on my bench to become a Mini Old School Cool.

 

[Aksrockets]

Optimize and ACME fincan? I think that's a bit of an oxymoron. What mods are you doing?

An easy way to optimize is reduce dead space, that usually means straying from the 3 point dual deployment system. Use a cable cutter, or just fly single deploy and drop it fast (this depends on where you're flying though).
Here's a design I've grown a bit fond of. It's fairly optimized, but still very simple. Only about 1.5cal of dead space.
View attachment 276617

Alex

 

[AndersLT]

Optimize and ACME fincan? I think that's a bit of an oxymoron. What mods are you doing?

An easy way to optimize is reduce dead space, that usually means straying from the 3 point dual deployment system. Use a cable cutter, or just fly single deploy and drop it fast (this depends on where you're flying though).
Here's a design I've grown a bit fond of. It's fairly optimized, but still very simple. Only about 1.5cal of dead space.
View attachment 276617

Alex

The mods I will be doing is shorting the tip cord to 2.5cm and the height to 8 cm I will also lengthen the forward transition on the fin can to 5cm.

I know this is a bit strange that I am optimizing a rocket with a heavy fin can but for my first 54mm MD I would prefer to use a fin can for now.

When I get to the building faze I will get the final weight of the fin can because it will be lighter due to some material being cut off.


Anders


Edit: I'm also keeping the altitude down because the waiver is 12000 feet.

 

[AndersLT]

Forgot to mention I lengthened both upper and lower body sections.

When I'm done I will get the OR file posted

 

[AndersLT]

View attachment 54mm Md rocket TRF.ork

edited file.

Performance/specs:


Stability: 2.25-1.75 cal


Speed: mach 1.40


Altitude: 12268 feet


Length: 133 cm


Weight: 2941 grams loaded


Anders

 

[KenRico]

December 19th is a ways away ... my suggestion is too build two rockets the same length .

One using the ACME (AKS says not optimized) fin can and some 54mm Blue tube or LOC tube with a wrap ..or sleeve inside a Blue Tube 2.6 inch tube for 'Almost Min Diameter'

After flying and having good deployments and tracking , ect then build the go for it rocket .

Then build a true MD with the Proline 54MM tube and hopefully metal tipped VK nose cones with coupler.

Kenny

 

[AndersLT]

December 19th is a ways away ... my suggestion is too build two rockets the same length .

One using the ACME (AKS says not optimized) fin can and some 54mm Blue tube or LOC tube with a wrap ..or sleeve inside a Blue Tube 2.6 inch tube for 'Almost Min Diameter'

After flying and having good deployments and tracking , ect then build the go for it rocket .

Then build a true MD with the Proline 54MM tube and hopefully metal tipped VK nose cones with coupler.

Kenny

Great idea but I think I will just build 2 booster sections.

 

[AndersLT]

Here's the plan:

I will build the rocket with the acme fin can then later on when I'm more confident with DD and T2T I will build another booster segment for this rocket and replace the NC to a metal tipped one. On the second booster will be longer to fit a 6 grain case and fully optimized for larger launches.

 

[AndersLT]

Updates:

All parts ordered except altimeters.

I'm choosing to use a cable cutter now because I have the system so why not.

I'm switching the adept 22 out for the Eggtimer TRS.

It is now a signal break system.

I'll make another booster without the acme fin can later but first I'm using the fin can.



I will do a separate build thread when I start to assemble the rocket