Loki M1378 vs MAC canvas phenolic?

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Andrew_ASC

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So yeah I started looking into a L3 design for fun. A 3FNC 54mm min diameter dual deploy canvas phenolic rocket. Three CF fins of 0.1275” thickness that theoretical flutter at M3.45. Rocket is about 189 cm long and 2.27 stability margin. It predicts M2.89 and 36,700 ft in OR. I’m at work on break but curious if any has pushed MAC phenolic tubes above M2.4!?? From what I have read the canvas phenolic survives M2.3-2.4 from others flight data. Is this a feasible L3 project idea?

I really dig the light density of the canvas. And price isn’t bad.
 

Cl(VII)

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A rocket similar to what you describe has been built (carbon versus canvas though), but I don't know if it has flown yet...read and learn young one. Mac Pappy

While it is carbon airframe, the size limitations of the 54mm airframe, and how to fit everything are laid out well.
 
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blackjack2564

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Mac Pappy has carbon airframe .

Ps. I would just call Mike and ask him for an opinion.
 
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ECayemberg

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Checking in! Mac Pappy has flown! Since it didn't get lit at Airfest '17, it took flight on Sunday of Airfest '18. Nominal flight up and down....

except...

the M1378 spit the nozzle insert, which limited the altitude to about 60% of the expected altitude (23k vs. 38k'). I believe Scott has the nozzle issue resolved now.

My personal hunch is:

Canvas will work well under ideal conditions. IE: if the rocket flies straight, doesn't cone, doesn't encounter significant wind shear, early or late deployment, it will hold up just fine.

However, if the rocket airframe experiences any exceptional forces other than directly in the direction of travel (see above), I'd be surprised if it didn't shred. Side loads and yaw forces would likely be problematic for canvas, IMO. Planning for less-than-perfect atmospheric or flight conditions, I'd lean heavily towards carbon (or glass) airframe.
 

Andrew_ASC

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I’ll call Mike for an opinion to see if his customers have pushed his product this hard. I think the canvas phenolic is tougher than normal phenolic. I don’t want to bash his product if it works at M2.89. Fiberglass maybe a better economy alternate for this environment. Anyways thanks guys for the advice. Not out to set a record. Just trying a method where what I learn at L1/L2 transitions to L3 build.

I’m thinking unreinforced airframe whatever I do. And not tip to tip.
 

mike2wander

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Checking in! Mac Pappy has flown! Since it didn't get lit at Airfest '17, it took flight on Sunday of Airfest '18. Nominal flight up and down....

except...

the M1378 spit the nozzle insert, which limited the altitude to about 60% of the expected altitude (23k vs. 38k'). I believe Scott has the nozzle issue resolved now.

My personal hunch is:

Canvas will work well under ideal conditions. IE: if the rocket flies straight, doesn't cone, doesn't encounter significant wind shear, early or late deployment, it will hold up just fine.

However, if the rocket airframe experiences any exceptional forces other than directly in the direction of travel (see above), I'd be surprised if it didn't shred. Side loads and yaw forces would likely be problematic for canvas, IMO. Planning for less-than-perfect atmospheric or flight conditions, I'd lean heavily towards carbon (or glass) airframe.
I think Eric hit the nail right on the head. When in doubt go with carbon. I've personally flown my HYPER 54 to Mach 2.3 (1822) and 23k on an L1040. With the Loki 2800 case loaded there is absolutely no extra space inside. The motor acts as an aluminum liner for the canvas airframe. A longer canvas airframe to hold the Loki M1378 spit would be the same situation. If surface mounted fins were to experience a lot of flutter then I think the rules would definitely change. On the flip side....With a MAX-Q Fin Can I think the canvas would survive as long as deployment goes as planned. I think someone needs to prove us right or wrong. ;) The pics of Eric and MAC Pappy were taken at Airfest in Argonia last August
Cayemburgh carbon.jpg cayemburgh carbon2.jpg
 
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DavidMcCann

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Going for cert knocks out the fin can.

I'd go carbon here, but as Mike said.... there's not a whole ton of open space in a rocket like this. You're basically pulling a canvas condom over a motor casing and lighting the bottom.
 
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