Discussion in 'Scratch Built' started by neil_w, May 28, 2019.
Is that a rule now? If so then I am...
Can always use GIMP. Overlay the actual rocket picture on the space background from the sim pic, you know, for the face card.
Oh... I thought Nytrunner meant it had to be shot on location...
Weighed the finished rocket at 2.7 oz, vs. 2.4 in OR. Not bad. Still building a bit heavy, maybe just all the glue and paint. CG came out about an inch behind OR. Still yields a bit over 1 caliber stability with a D16, so I'm feeling pretty good about it.
*Hoping* to launch it next weekend.
Wow, that is quite good agreement, about 10% variation sure isn't much at all. I'm impressed that it is so light, with so many glue joints, paint surface area, and details. That should fly quite well! Will it be a D16 for the maiden flight? I hope it works out next weekend.
No first flight will be a C6 or C12.
Hoping for a straight trail and soft landing!
I never thought of this until just now: what if one edited the parts and materials databases to account (approximately) for the weight of finished parts? Instead of weighing, for example, a foot of BT50 and entering the observed mass per length, do that to a piece that's been filled, sanded, primed, sanded, etc. How much closer to final weights and CGs could one come that way?
It certainly wouldn't work for bulk materials. I don't know about OR but I guess it's probably the same as RS in that for many items one specifies a bulk material, like Balsa for a fin for example, and then the planform dimensions and thickness. One would have to change that to 3/32 balsa, 1/8" balsa, 5/32" balsa, etc. each as different materials. Maybe worth it if the results are good.
That is certainly doable, although plenty of work to figure out the numbers. Also, different folks finish things differently, so there are a lot of variables to take into account.
What I'd probably most like is for the program to have "finishing" as an optional switch... I.e, if I choose "heavy paint" as an option, it'll add paint weight (and distribution across the object) according to the area of the object. They already have paint finish as an option to set surface friction, but this would be somewhat more complex.
Then there's glue, which might be more important because there's usually more of it around the fin can and engine mount, and that brings CG back. The finishing adds weight but it's pretty well distributed, and probably doesn't move CG much (although there is at least a bit more paint in the rear).
It would definitely be nice to have these options, but whether it is worth the implementation effort is unclear.
I do already have a custom material for 1/8" papered balsa, since the papering adds very noticeable weight. I use it for 3/32" as well because the density difference is small, and I don't mind slightly overestimating the weight of the wood in the tail. But I haven't factored in finishing or glue, beyond that.
PDII flew yesterday at the RadRocks launch. @mbeels and @jqavins were there to witness. The flight was OK, but weathercocked into the gusty wind and didn't fly as vertically as I would like. But it went up and came down safely, and the launch lug stayed secure, so I'm happy. This one will fly again.
Marten's PD2XL flew as well, and it was awesome.
Having now flown successfully, the PDII assumes its place on the rocket wall:
The rocket wall is running out of room.
It looked to me that it boosted very straight, after a small weather cock just after it left the rail. I think that the wind is to blame here, it flew straight and true after that. These two photos seem to capture the weathercock.
Yup. I'll be trying a QuestJet next time if there's wind. If it's calm, the C6 should be fine.
More reason to build a rocket ROOM.
I kind of suspect that you have a secret lair inside a dormant volcano to store all yours.
Here's the launch phase of the D16 thrust curve:
That's a darnsight better than a C6, but if weathercocking is really your worry, compare it to the D10:
Good fin-body adhesion gets a bit more important with that D10! More likely to approach "the speed of balsa"!
Given his location, that's not so farout a theory.....
D10 isn't near the speed of Balsa. I've tried
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