Best Strength/Weight Airframes for Mach 2+

Wildman Rocketry
eggtimer rocketry
rocket sok
The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
TomSmith58

TomSmith58

Well-Known Member
Joined
Dec 15, 2013
Messages
348
Reaction score
2
I am kicking around ideas for my first scratch built. I am looking at carbon, fiberglass, and various organic formulations like Blue Tube and Magna Frame. For nose cones I am looking at various plastics as well as carbon and fiberglass.
I have asked vendors for the weights of their carbon parts but I am not receiving a response. I don't know how they compare with fiberglass but I assume they are lighter. By how much?

I am looking at 29,38 and 54mm.

My question to the group is what materials do you think are needed for Mach 2 and for Mach 3 flight.

As I build rockets in Rocksim and fiddle with the weight I see that I must have a light rocket to reach Mach 3.


Sent from my iPhone using Rocketry Forum
 
TomSmith58 said:
I have asked vendors for the weights of their carbon parts but I am not receiving a response. I don't know how they compare with fiberglass but I assume they are lighter. By how much?
Click to expand...
Based on what I've been able to intuit from final rocket weights, there are no commercial carbon tubes in small diameters that are much lighter than the fiberglass equivalent.

If you want a really light, strong tube, either from fiberglass or carbon, you have to make it yourself.
 
mikec said:
If you want a really light, strong tube, either from fiberglass or carbon, you have to make it yourself.
Click to expand...

So Mike,
I think you are suggesting thinner walls that are commercially available am I correct? My Mariah has an .062 thick wall. Certainly it would be lighter if I could make a thinner wall. Is that what you are getting at?

What about G12? Filament wound should be stronger than cloth by a bit but not lighter if they make it the same thickness. Do they?



Sent from my iPhone using Rocketry Forum
 
1. Don't use Rocksim for supersonic simulations. It simply isn't accurate.

2. The best strength-to-weight airframe material is no airframe: let the motor case handle the loads. You do have to make your own nosecone then, though.
 
CarVac
Bond fins directly to the motor case?

With that idea I envision an Aero Pack style retainer that reacts the thrust loads and anchors the shock chord. Then a body tube could slip over the top of the engine by say 2-3 body diameters. Inside the body tube is a ring that rests on the retainer. That gets rid of a lot of body, especially if I go with a 6g or 6gxl motor.


Sent from my iPhone using Rocketry Forum
 
TomSmith58 said:
So Mike,
I think you are suggesting thinner walls that are commercially available am I correct? My Mariah has an .062 thick wall. Certainly it would be lighter if I could make a thinner wall. Is that what you are getting at?

What about G12? Filament wound should be stronger than cloth by a bit but not lighter if they make it the same thickness. Do they?



Sent from my iPhone using Rocketry Forum
Click to expand...

It depends on where the loads are being applied and the specific layup of the tubing. You can't rule out one as being stronger then the other. You may be able to roll a tubing with a lower resin content then PR tubing, which would result in a lighter, stronger finished product. You might be able to orient the fibers in a way that would mean you need less of them to have the same directional strength as a PR tubing (which I imagine would not be difficult)
PR filament wound tubing lacks a 0° winding layer that would be beneficial in compression strength along the length of the tube (scenarios such as a high stress flight). It also lacks a 90° filament layer which would be beneficial in compression strength opposite to the length of the tubing (scenarios like a hard landing in a flat spin). If you know the forces your rocket will encounter, you can better utilize fiber directions for a lighter, stronger tube tailored to your specific flight profile.
Rolling your own isn't too difficult. If I had a bit more cloth I'd offer to make one for you.

Alex
 
With an offer like that I'd have the cloth shipped to you and you could keep the overage. Do you know the weight per foot you could get for 29, 38, and 54 mm? If you know just one I could estimate the rest.


Sent from my iPhone using Rocketry Forum
 
Aksrockets said:
It depends on where the loads are being applied and the specific layup of the tubing. You can't rule out one as being stronger then the other. You may be able to roll a tubing with a lower resin content then PR tubing, which would result in a lighter, stronger finished product. You might be able to orient the fibers in a way that would mean you need less of them to have the same directional strength as a PR tubing (which I imagine would not be difficult)
PR filament wound tubing lacks a 0° winding layer that would be beneficial in compression strength along the length of the tube (scenarios such as a high stress flight). It also lacks a 90° filament layer which would be beneficial in compression strength opposite to the length of the tubing (scenarios like a hard landing in a flat spin). If you know the forces your rocket will encounter, you can better utilize fiber directions for a lighter, stronger tube tailored to your specific flight profile.
Rolling your own isn't too difficult. If I had a bit more cloth I'd offer to make one for you.

Alex
Click to expand...

Even ignoring the non optimal wind angle (iirc 54.5 on PR) you could make a more optimized (i.e lighter) tube by not abrading the OD post cure. The mean fiber length of PR tubes is cut way down when they're ground.

Getting good compaction and fiber orientation doing a hand layup is going to be difficult vs filament winding, however. You can mitigate by using high strength carbon and working meticulously. On the bright side you can preferentially add a lot of high angle fiber.

The lightest option is to, as CarVac said, eliminate the BT all togther and throw a fincan on the case. If it had to be done, carbon is the clear winner.
 
TomSmith58 said:
I think you are suggesting thinner walls that are commercially available am I correct? My Mariah has an .062 thick wall.
Click to expand...
If you look at altitude record-setting rockets, in many cases they were made with hand-laid carbon (both the tube and the nose cone) and I suspect the wall thickness was significantly less than 0.062.

Commercial G12 is strong but certainly very heavy. They could make it thinner but typically don't (the only exception I know of is the thin-wall tube Wildman uses in the Mini series.)

Of course, most rockets are built for altitude, not speed. For altitude you typically want an optimal mass (too light is as bad as too heavy) and in that case you may not need to save weight much.
 
TomSmith58 said:
CarVac
Bond fins directly to the motor case?

With that idea I envision an Aero Pack style retainer that reacts the thrust loads and anchors the shock chord. Then a body tube could slip over the top of the engine by say 2-3 body diameters. Inside the body tube is a ring that rests on the retainer. That gets rid of a lot of body, especially if I go with a 6g or 6gxl motor.


Sent from my iPhone using Rocketry Forum
Click to expand...

Make a coupler diameter airframe with integrated bulkhead that bolts onto a tapped forward closure. Avionics in the nose, recovery in the abbreviated airframe.

The fins would be mounted on a short fincan that slips over the motor case.
 
5" min dia 72" propellant
5together.jpg


98mm min dia 60" of propellant
Ode.jpg


75mm 45" of propellant

Balls2010.jpg


Tony
 
Tony
What are your fin cans made of? Did you buy them as is or build them?
Tom


Sent from my iPhone using Rocketry Forum
 
Last edited:
Was the tube fiberglass as well? I don't understand the 1/3, 2/3, 1 nomenclature. Could you explain that please?


Sent from my iPhone using Rocketry Forum
 
a lot like this..but with 5.7 oz CF. The below video is part of a series of videos. The rocket Tuff Enough was to prove you can do extreme flights with hand laid fiberglass and "boat" epoxy. It has flown to 37K and Mach 2.2

[video=youtube;PtYYsX3VEmc]https://www.youtube.com/watch?v=PtYYsX3VEmc[/video]

Tony
 
TomSmith58 said:
Was the tube fiberglass as well? I don't understand the 1/3, 2/3, 1 nomenclature. Could you explain that please?


Sent from my iPhone using Rocketry Forum
Click to expand...


What he is talking about is the fins are covered with a layer that is 1/3rd the size of the fin followed by a layer that is 2/3rds then finished with a layer that is full size. It makes the fin stiffer but adds less weight than if you covered each side with three full layers. It is also more aerodynamic because it is thinner at the leading and trailing edges.
 
Tony, how do you attach the fin can to the motor case? Or the forward body tube to the case?
 
I have an idea how it might be done. Use a slimline motor retainer on the aft end of the motor to retain the fins to the motor. Then use an Aero Pack internal minimum diameter retainer at the top of the motor to hold the nose and upper airframe on. Make the upper airframe long enough to overhang the internal retainer by 2 diameters. Use the 2-56 nylon screws through the airframe and into the internal retainer to hold it on during launch. The only thing I don't know how to do is keep the fin can from rotating.


Sent from my iPhone using Rocketry Forum
 
TomSmith58 said:
I have an idea how it might be done. Use a slimline motor retainer on the aft end of the motor to retain the fins to the motor. Then use an Aero Pack internal minimum diameter retainer at the top of the motor to hold the nose and upper airframe on. Make the upper airframe long enough to overhang the internal retainer by 2 diameters. Use the 2-56 nylon screws through the airframe and into the internal retainer to hold it on during launch. The only thing I don't know how to do is keep the fin can from rotating.


Sent from my iPhone using Rocketry Forum
Click to expand...

No slimline. The thrust ring on the motor is all you need to retain the fincan.

Also, no Aero-Pack internal retainer. It is too large for this purpose: it's the same size as the motor case itself. This method requires all-custom parts.
 
Is it necessary to prevent the fin can from rotating? How about is it necessary to prevent the fin can from riding up the motor case? That could be an issue during recovery.


Sent from my iPhone using Rocketry Forum
 
TomSmith58 said:
Is it necessary to prevent the fin can from rotating? How about is it necessary to prevent the fin can from riding up the motor case? That could be an issue during recovery.


Sent from my iPhone using Rocketry Forum
Click to expand...

It's not necessary to prevent the fincan from rotating. If it bothers you, then force-fit it over some blue tape.

The fincan won't really ride up the motor case because of drag and stuff. It's really unlikely to be an issue, but if you are worried then force-fit it over some blue tape.
 
jmight said:
Tony, how do you attach the fin can to the motor case? Or the forward body tube to the case?
Click to expand...

the fin can is 'attached' via friction fit with masking tape. The forward is not attached as it is a separation point for a recovery event.

Tony
 

Similar threads

Joey Draney
fiberglassed rocket to mach 2
Replies
4
Views
792
Handeman
Handeman
Joey Draney
Mach 2 attempt
2
Replies
59
Views
3K
OzHybrid
OzHybrid
amiliv
Stripping force for threads tapped in fiberglass sheet
Replies
21
Views
906
Belrock
Belrock
M
SBR Fusion 4" build weight?
Replies
8
Views
468
mach0_001
M
pyrrxa
Mach 2 Modification Sanity Check
Replies
4
Views
562
Keener
Keener

Latest posts

Back
Top