L3 Airframe Material?

Johnly

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Over the decades I think I've built L3 airframes out of all the conventional materials except PML Quantum Tube. The choice comes down to the airframe design and flight profile. Cardboard tubed stubby, large diameter airframes for M powered lob flights work just fine, while the same material used in high L/D ratio airframes often results in inflight flexing and rapid disassembly.
Another aspect is how often you are planning on flying the airframe. Once and retirement or flights with lower total impulse motors have different needs than an airframe that you're expecting to fly over and over again on M motors. My ARLISS airframe has ~20 flights on it and is ready for more due to its fiberglass airframe and replaceable fins. Other ARLISS fliers might have over 50 M flights on their fiberglass airframes.
 

PSLimo

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I built my level 3 rocket 15 years ago with regular Loc tubing. It's very similar in size to what your thinking at 7.5" x 9.5'.

It survived the test of time and has flown many times with different owners since then and is still flying today. Here's Its maiden voyage in a video shot by Justin.



Good luck with your level 3!
 
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I guess for people being real cheap skates They always seem to take something like Sonotube or cardboard tubing which has to have fiberglass laid over top of it , a very laborous and costly process, and lots of heavy fiberglass resin to get it to soak in, vacuum bagging, etc. Then you end up with something that is very rough on the surface, takes a whole lot of filling and sanding, and is heavy. Life is way too short to have to spend a portion of it going through all of that stuff, just to end up with something that is still inferior to fiberglass. Fiberglass is the way to go, it's tough as a Gorilla, and has a smooth finish that's ready for paint. That's worth its weight in gold right there.
So youre too good for cardboard? Is that what youre saying? All of us who use cardboard are peasants in your eyes? Just curious as to what you're really saying
 

Philip Tiberius D.

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Mostly we add the FG to Cardboard for durability...on the trip to and from the field.
So. I wrapped a LOC 4” Goblin in 4oz FG with 3:1 LOCPoxy - followed their video. Wrapped in Mylar - Let it set for 8 hours, Mylar is stuck. On advice from someone with many more years FGing cardboard I let it sit longer (6 days - away from home so that was easy). Mylar still stuck to FG. Do I sand it off with 120 / 180 grit. Rough it up with 400 grit, lay down some adhesion promoter and paint the Mylar ? Try again with thicker Mylar ( this is 1 mil thick). Thoughts…
 
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Freezer spray on the mylar or get an edge up and get some water under it without wetting the cardboard tube. This can allow wicking between the mylar and FG and act as a separator. I've used that to release prints from a glass bed.
 

mtnmanak

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I don't think it really matters which material you pick for Level 3. I have flown Level 3 motors in cardboard, phenolic, fiberglass, etc. and have had a blast doing it.

What always surprises me is when people start asking about Level 3 and want to know how to do it cheaply. Unless you are into EX and are going to make your own propellant, 2 or 3 Level 3 flights are going to cost more in commercial motors than the rocket regardless of what material you choose. If you go with a non-glassed cardboard kit like the LOC VII, a single M motor is very likely going to be more expensive than your rocket.

So, if you are going to get your Level 3 and fly an M motor one time, just to get the cert, that is cool and I can see why you would want to cut costs on the rocket. If you plan to get your cert so you can fly Level 3 motors frequently, then your real challenge is figuring out how you are going to budget the expense of motors, not the cost of the rocket.
 

FlyBy01

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I have had an L2 for 22 years & finally want to try for L3. What airframe material should I use for a 7.5" x 9' rocket? LOC cardboard, fiberglassed LOC cardboard, phenolic, fiberglassed phenolic, Blue Tube, G-12 fiberglass, etc. I know L3 costs $$$$$$ - I have already bought AT 75 mm motor hardware, electronics, GPS, etc., but G-12 fg airframes seem quite spendy.
Thanks!!!!!
I would use a fiberglass rocket based on by the time you would spend to fiberglass a Loc Precision rocket how much did you really save? A Loc VII is about $275.00 and if your apart of the Wildman Club a 4" Wildman Extreme is $337.00. The Loc in theory has everything you need in one kit minus electronics but when you fiberglass it a bigger parachute would be advisable due to the added weight. Choose the path you are most comfortable with and have used for the last 22 years.
 

Neutron95

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I don't think it really matters which material you pick for Level 3. I have flown Level 3 motors in cardboard, phenolic, fiberglass, etc. and have had a blast doing it.

What always surprises me is when people start asking about Level 3 and want to know how to do it cheaply. Unless you are into EX and are going to make your own propellant, 2 or 3 Level 3 flights are going to cost more in commercial motors than the rocket regardless of what material you choose. If you go with a non-glassed cardboard kit like the LOC VII, a single M motor is very likely going to be more expensive than your rocket.

So, if you are going to get your Level 3 and fly an M motor one time, just to get the cert, that is cool and I can see why you would want to cut costs on the rocket. If you plan to get your cert so you can fly Level 3 motors frequently, then your real challenge is figuring out how you are going to budget the expense of motors, not the cost of the rocket.
The cost of motors was one of the big considerations with my in progress L3 build. I decided to go with a relatively small 4" fiberglass kit that will comfortably fly on a wide range of L2 motors, and will make the most of the available waivers in my area on a baby M.
 

Philip Tiberius D.

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The cost of motors was one of the big considerations with my in progress L3 build. I decided to go with a relatively small 4" fiberglass kit that will comfortably fly on a wide range of L2 motors, and will make the most of the available waivers in my area on a baby M.
Just curious what frame / kit you went with? I’m with you, I’d love to fly 98’s all day but my field and especially my bank account can’t handle it.
 
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