R.E.A.R. showcases the art and science of model rocketry for research and recreation. Hosted by veteran rocketeer and astrobiologist, Dr. Dave Thomas.
Check out my other channels as well: Caving with Dr. Dave: ru-vid.com/show-UCwHQn12PCyEg0C3a-1ZuHpA Space Exploration with Dr. Dave: ru-vid.com/show-UC6yNuszXXlwjgPlrzm_NFaQ Traveling with Dr. Dave: ru-vid.com/show-UCD66Tv7I_VuBZJAnL67T7yA Dr. Dave Thomas (personal channel): ru-vid.com/show-UCyI_O4vS0kBQi1yQUjnVvrw
Here is a video of my flights this weekend... some success, some failure... how rocketeers learn. Thanks for advice as always ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-XbvbFa8UNrU.html
Dr. Dave... I was wondering... the rocket I plan to make will be about 4' high with a body thickness of 2.5", the question I have is can my parachute be too big? I plan to use a totes style umbrella for the chute material... is there a formula for the parachutes relative to the bodies that is ideal? I know in the case of most rockets you have made go between a 12-18 inch parachute... I figure that the size of the umbrella is prob a bit more than that..... thank you
Offhand I recommend a 24-30” parachute for that size of a rocket. I suggest using OpenRocket to simulate your design. It will show the performance of different sizes of parachutes.
Dr Dave, i have a couple of more construction questions...i am planning to make a parachute for a rocket I'm designing out of umbrella material like you did in a video... is there a ratio i need to use for the shroud lines....i.e. the lines should be 3 times the diameter of the parachute or what not.... btw I'm making a windsock out of umbrella material and a dowel rod to assess field conditions.... second question.... i see you assemble most parachute kits with shroud lines being tied to adjacent corners.... but in pre assembled parachutes they tie the shrouds two adjacent corners on the outer corners and across the middle of the chute material for the center shroud line... is there any difference in your educated opinion? Thank you
For the parachute, I use shroud lines 1.5x the diameter. You are correct that most preassembled parachutes have a string across the middle. It’s supposed to decrease tangling a bit, but it’s also a longer string than the other two. In practice, I haven’t seen much difference.
@@REAR_rocketsalso.... your opinion....since i was thinking of using eyelets at the corners and kevlar for the shroud lines... if i used the eyelets in the umbrella material, and used crazy glue for the kevlar knots could that work for the parachute assembly? Thanks as always.
That cable, crimping and shrink tubing is dubious at best? Why not just braided kevlar, it be lighter? Plus that whole huge elastic shock cord also. Is that really needed?
I'll know more after I launch it. This whole recovery system is different from anything I've built before. Theoretically, the combination shock cord should be easier on the rocket as long as it doesn't burn or get tangled. I think the cable was completely superfluous, but I'll reserve judgement until after a few flights.
My rocketry career started with the Alpha 3. This was way back in the mid 70s. I remember having to cut each fin out of the die cast balsa sheets and having to cut the shroud lines from a single length of string. On the balsa fins I remember using sanding sealer and trying to shape each fin to a perfect airfoil shape.
The kit reminds me of the Alpha 3 but with 4 fins.. I started flying in the days of having to cut out the fins from a die cut balsa sheet and aligning the fins with a pencil line on the body tube.
If i have a shock cord that snaps... is there a rule of thumb if i choose to tie a length of kevlar to the remaining cord? I know you said kevlar was 3x the overall length but not sure if adding more... or could i even tie an extra elastic shock cord where the break happened or would that be bad? Thanks as always dr Dave
If it started with a rubber shock cord and an Estes type glue-on anchor, it's usually easiest to cut out the old cord and anchor and replace it with new elastic/rubber. Kevlar can rip through an Estes mount. Tying Kevlar onto the remains of the elastic shock cord probably will end up breaking at the elastic again.
Dr dave... crazy question... i am trying to scratch build a rocket as i said before... cant find a coupler big enough... would it work if i took a tube i wanted to use and glued more paper on to it in layers to beef it up? Or would that not be ok structurally? And if i can would that be bad to use as a baffle assembly if i have to beef it up like i want to for the coupler?
Yes, you can make your own baffle from a tube coupler and two wood or heavy cardboard disks with offset holes in them. As I recall, there are instructions in the Handbook of Model Rocketry. For wadding I use a thickness of twice the body tube diameter (loosely crumpled.)
Dr dave i watched your franken rocket video... i plan to make a model rocket using two of those long candy/bank tubes and a 3d printed nose... i am wondering is there a rule of thumb for motor mount tubes as i am designing the rocket in open rocket and not sure how big a motor to install i know once i know for sure the centering rings will design for me in a way based on the body tubes, also in a larger rocket which is better a launch lug, or a rail system?
Start with whatever motor mount is handiest and see how it performs in OpenRocket. Adjust up or down as necessary. Rod or rail is up to what you have for a launcher. Rails are more stable but rods are much less expensive. I use both.
@@REAR_rockets i trust your judgement if you say it may not work it may not... though gives an idea of getting one and dremeling the punch and testing on shroud material
dr. Dave, I am building a rocket from scrap materials from another kit, I designed it in open rocket and the simulation looks good... the only questions I have are thusly 1) with a baffle system, which I grabbed from the rocketarium chief ii kit, do I need vent holes for the rocket? 2) with the baffle system, and the fact that I am giving it a kevlar shock cord, I don't need to pack any wadding in the rocket for launching right? thanks your videos are very informative.
@@REAR_rockets thank you... It will be interesting as i learned for its smaller size a b 6-4 would be too strong... open rocket said a b4-2 would work though
Dr Dave... what was the shock cord ratio if you replace elastic with kevlar again as i dont remember which video it was but scarcely thought it was that the kevlar needed to be 4x the elastic length. Ty
Dr dave what is your thoughts on powder? Dad used to put powder in his rocket bodies to make the recovery system pop out easier? Is this a thing or a waste of time? Thanks as always
I’m about half way through my build. Your videos are great. Thank you for the excellent work. I have to agree with the one comment, the music during the fast forwarding could be eliminated.
Great build video. The Estes Hi-Flyer XL deserves up powering to 29mm, through tube fins, a rail guide for minimal diameter performance, ejection baffle and add nose weight. Enjoy the conical exhaust contrail approaching the speed of sound on a budget.❤
Dr dave i made a fin system for applying sanding sealer you can try if you like... i took a small square of wood, about 5"x5" and glued clothes pins around the wood facing up to use as clamps for the pins... worked well for me.
Cool rocket. I just built the Apogee TTV. It is also a medium powered rocket that has an avionics bay. But it is for timed staging. Katana Jr may be my next rocket. Thanks for the detailed assembly videos.
