The name is an acronym from the first names of my wife, 2 daughters and my son (a 7 year old yellow labrador 😀 ) Just thought I'd get that out of the way since it looks to be spelled funny.
The first question I have is about railguides. I have never used a rail before, but I plan to build all my high power kits for rails, since they make sense to me and things seem to be moving that direction. So should I just use rail buttons? Screwing a rail button into a phenolic, cardboard or quantum tube even with a bit of epoxy just doesn't seem very secure to me. As many of my kits are PML, and I use the pistons, a blind nut on the inside is not an option either. I would welcome suggestions.
Next question along tha same lines is what type of rails do we have? I do like the acme conformal rail guides from Giant Leap rocketry. Securing these with JB Weld seems very secure, but I do not know if they are compatible with the club rail systems.
The last question for now is on chute sizing. Current dry weight according to rocksim is 106 oz. I have already weighed and adjusted all the major parts to be sure the weights are accurate, the only "assumed" weights in that total are for the chute itself, and paint & epoxy. Anyway, I really don't have a feel what decent rate I should be targetting. The rocket will be simple motor ejection, and it sims up to about 3,560 feet with a J350. I plan to use either a Skyangle, a TAC-1 or a stock PML chute. I don't mind paying for a nice chute that will last, as long as I can get the size right. Again any suggestions are appreciated.
First, the Acme rail guides will work fine with all but the largest rails the club owns, so no worries about that. I use them myself on pretty much all rockets under 8 or 10# except for extreme altitude birds which I fly out of a launch tower instead of off a rail or launch rod.
The club own regular 80/20 rails and an Extreme Rail for larger projects.
From what you're saying, you're probably fine on the chute. Maximum descent rate according to the safety code is 32 feet per second, a preferred rate is in the low 20's. Much below that and you could watch it drift over the horizon as it rises on a thermal. It's a 1/4# rocket, I wouldn't go much above 24"
Warren Musselman
Webmaster
I'm sorry Warren but I don't understand your chute example. What is 1/4#? Does that mean 1/4 scale or 1/4 pound? As I said above, the dry weight is about 106 oz. or roughly 6.5 lbs. The 38/720 hardware weighs about another 1/2 lb giving me a total weight on decent of roughly 7 lbs. I was planning on using a 44" SkyAngle which should give a decent rate of about 21.5 fps. Does that sound about right? For this flight I would rather be a bit conservative, I don't mind walking a bit extra if it gets my rocket down safely.
21fps sounds just about perfect as a descent rate. My example was 1/4#, meaning a quarter pound. My mistake - I misconverted thinking grams instead of ounces. (All my rocket weights are in grams and kilograms - never pounds)
I'd say if you're simming 21fps as your descent rate, you're fine as far as chute size.
Warren
agreed. Occasionally, I will go a little faster or slower, but with HPR, aim for about 20fps or so.
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