It's been a while, and I forgot about your beautiful assembly drawings.
Is the long coupler, item 6 on sheet 3, for structural reinforcement? If so, I think it's overkill, unnecessary weight. As we all know, most LP rockets use stock tubes with no such reinforcement and do fine, unless they dirt dive. Will the coupler add enough strength to survive such an event? Is that your purpose?
Finally, aren't the leading end chamfers on the launch lugs backwards? Don't you want the lug profile to be a trapezoid, not a parallelogram?
I'll be interested to see how well that comes out. I'm sure you won't get as much restraining force as you did on those fins. Will it be enough? Tune in next time to find out on Lake Roadster's Build Time.
From the pictures in post #39, it looked like the structure was OK and you just needed to fill the divots. So maybe filler would be a better choice than any brand/type of glue.Note: Use Elmer's School / White Glue for an surface repairs.
From the pictures in post #39, it looked like the structure was OK and you just needed to fill the divots. So maybe filler would be a better choice than any brand/type of glue.
Looks great. I am still going to use Pringles cans, Oatmeal Cartons, and Almond containers (the later have metal lids and bottoms, i was surprised to find the sides are paper/cardboard!)
big problem is weight——-not the rocket’s weight, but MY weight, I tend to get a bit tail heavy eating all that stuff. Plus I think SWMBO has already decided I am unstable no matter where my CG is.
<----------- No worries, no RSO....Clever design for a staged Alpha or Ahpla the vented ring fin is pretty cool. Only problem is if you might have a public health scare at a public launch when the RSO announces that we have an "Alpha Variant on the field," but we are supposed to keep that topic quarantined in the existing CoVid forum here.
I am not The most scientific on my design and construction. I have RockSim and OpenRocket and have never really used them. I can claim a partial excuse because most of my designs are square or triangular cross sections or have other weirdnesses that don’t lend themselves to sims (the rest is pure laziness on my part.)
that said, I probably have more experience with scratch built gap stages than most.
tenets I subscribe to are as follows
at least two vents, equally spaced, so there is no net lateral force from the staging gas that might throw the rocket off kilter. I have no evidence it makes any difference, I just do it.
I DO believe the position of the holes relative to the sustainer IS critical, the holes should be just below the nozzle of the booster. Depending on how you “mate” the sections, the holes can be in the sustainer, the booster, or both. If you are not going minimum diameter, I DO believe it helps to extend the internal motor mount to “duct” or route the hot gases so they illuminate the nozzle on their way out. My sustainer ignition rate is pretty much 100%, my major failure has been when I tried to extend the gap from 53 to 72 inches. 53 worked in flight multiple times, 72 worked on a test stand but failed in flight, not sure why. I was using a D12-0 on the booster, I now have some F15-0s and hope soon to try a build with a 72” gap.
as for the size of my holes, I just use a regular Note paper size hole punch, not for any scientific reason, just because it’s convenient.
I did. Fixed.Thanks for the detailed response.
"the holes should be just below the nozzle of the booster"
Is that what you meant to write? You meant sustainer, correct?
venting out the back is cosmetically and probably aerodynamically the best route for non-minimum diameter rockets, and Glen is exactly right, if you do this you need to run the motor mount of the BOOSTER (I checked, Lake!) to about 1/8 to 1/4 from the nozzle of the SUSTAINER.If you have enough room, you could vent through the centering rings out the back of the booster if you don’t want to put visible holes on the outer body tube. Then you might want the booster to have a longer motor central tube that gets closer to the sustainer nozzle.
depending on how close they are, you might not need a vent, but it does help, this 24mm stager does not appear to be vented and it has a short gap between the motors, for example:
https://www.apogeerockets.com/Rocket-Kits/Skill-Level-3-Model-Rocket-Kits/Rip-Roar
I did. Fixed.
Thanks!
I didn’t save the correction. been a bad day. They should be behind the nozzle of the SUSTAINER.Sorry but I'm still confused. Why would you want to put the holes behind the booster motor top end? If the pressure is pushing the ignition charge forward, it seems logical to have all the force going the same direction, well, logical to me anyway.
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