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TOPIC: Winter Project - Spring/Summer Level 1

Winter Project - Spring/Summer Level 1 2 months 4 days ago #2687

  • Robert Bantly
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Upcoming plans are for low and medium power and I will mostly stay there due to cost and ease of transport. This winter am going to try a home-designed Level 1 high power model as well as an inexpensive backup kit. Rather stunned at the amount of information out there. TMI? I think so!

For the kit, probably Apogee Zephyr or Aerotech Sumo - inexpensive and seem to be well-regarded. Recs?

For the homebuilt, am going to upscale a 1970's Estes kit. I understand the construction pretty well after spending some time reading instructions on how HP kits are assembled. Here are the questions!

Planning on using 75mm LOC high power cardboard for light weight and low cost. Build will be app. 61" long. TTW fins, plywood rings, flameproof cord, etc. Got all that. Avoiding phenolic, fiberglass, and carbon due to Hazmat for now.

Since the design I am up-scaling has swept-back fins, how do I keep the tips from being damaged? Light light weight, aircraft plywood, and adequate parachute are all on the list but I saw those asphalt landings at NARAM.

On fins, seems like most MFR's use 3/16" or 1/4" 5-ply. Would it be better to buy SIG 1/8" 5 ply aircraft plywood and laminate two sheets together for a very strong 10-ply fin? Their 1/8" 5 ply is awesome stuff. And would a layer of silk-span or other non-toxic covering assist in preventing tip damage? I had great results doing this on low power rockets and using dilute aliphatic resin instead of dope. Made them feel like plastic and didn't weigh much. Also understand that thicker fins are going to increase drag and thus aerodynamic stress on the rocket - something you didn't need to worry about with L + M power motors.

Will a hand-turned 76mm balsa cone stand up to Level 1? Very light weight if it will! I'll need to turn the nose to match the original kit.

29 or 38mm mount for level 1 and throw-away or reloadable?

The dreaded glue question - I KNOW that for joining cellulose - cellulose that aliphatic is super-strong. I also noted that epoxy is preferred for HP kits and for the engine mounting due to temp. Any suggestions? Is the epoxy just for quickness or is there a structural requirement?

Cheers / Robert
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Winter Project - Spring/Summer Level 1 1 month 3 weeks ago #2692

  • Allan Howard
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Hi.
Lots of ?’s! I’ll try to address some.
It was suggested to me to go with what you know and keep your cert flights easy. I realize that some will disagree with this and will want you to be “challenged”. However, my goal for my certs was to succeed first time, which I did. You can do more challenging things after you earn your certs, in my opinion.
Kits are just bucket of parts. Over the years I’ve modified most of mine anyway, primarily due to repairs. For my L1 I used my LOC/Precision EZI-65 kit. (I had flown it several times on G-80's). It had motor ejection of the main at apogee. (I’ve since modified it for dual deploy.) Now days, folks are using the Jolly Logic Chute release system.
For all my HP, except my L3 project, and much of my MP fleet, I use hobby epoxies for all of the parts, especially structural with good results. I have used JB Weld Steel for areas around the motor mounts since it has one of the best heat tolerances for epoxies.
If you beef up the fins, you want to check the CG. I use RockSim for my simulations. Although lots of folks are using OpenRocket. RockSim helps me choose an appropriate motor for my rocket. I like to go low and slow to be able to visually follow the rocket. So I look at the speed it leaves the rail (or rod) to make sure it’s high enough to be safe. And I don’t want to go supersonic as that requires more construction techniques, so I look at that. I like to be able to follow the rocket so I look at altitude. I was thinking of using my EZI-65 for my L2, but the smallest J put it up about 5000 ft. I didn’t think I could see that the entire way so I went with a larger PML Black Brant X kit with piston ejection. Again, I overbuilt the rocket and kept it “draggy” so I could follow it, again with motor ejection at apogee.
Balsa NC should be OK, but do check the CG. Depending on your fins and now NC, you may have to add nose weight and/or length to get a safe CG to CP.
While I’ve accumulated a number of reload casings over the years, I now fly mostly Aerotech DMS motors for HP. They’re about the same cost as the reloads (minus the casings.) If you go with reloads, think about what size motors you’ll be flying most of time.
I, too, have had some damaged fins on the pavement here. I would recommend a larger chute. Yes, I could have done that, but I didn’t want to risk going into the corn…so it was a tradeoff.
Good Luck.
Allan Howard
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Winter Project - Spring/Summer Level 1 1 month 3 weeks ago #2693

  • Robert Bantly
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All good thanks! Will probably roll my own and follow this and kit builds.
Cheers / Robert
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Winter Project - Spring/Summer Level 1 1 month 1 week ago #2714

  • Robert Bantly
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Made some decisions - ordered balsa from Sig for the nose cone. Will have to glue (4) 2" x 2" blocks together and install a hard wood dowel for a solid turning and anchor spot if no payload section is used. Also ordered two sheets of 3/32" 5-ply aircraft plywood and silk span. Plywood will be laminated into a 3/16" sheet for fin stock. Fins will be covered in the silk span for improved strength. In past times, I wrapped silk span around the fin leading edge "sometimes" with great results - have to ensure 100% bond or you get a crappy flappy edge. May just do sheets on this project.


I went down from 1/4" plywood due to the covering and it's probably a little over-kill with TTW construction. Thinner fin = less drag and less shred force too, if I am reading correctly. Need to score some LOC precision 75mm tubes - Apogee is out so I will have to do some surfing.
BTW: Level 1 build will be an upscale of Estes 1271 - Renegade, 1975 version. Currently building a 1:1 bash from a Mean Machine kit I hope to have at CIRFF. On both models, getting a PNC-60AH is the hard part. One is by bash, and the other is by lathe. No one makes this cone in larger sizes. Sad since it is on Red Max also, another popular Level 1 build.

Still "way" underweight on paper on the level one. Means a solid paint job and probably payload section, and maybe some weight at the end too.

Cheers / Robert
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