What did you do rocket wise today?

Sooner Boomer

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WooHoo! The Amazon driver finally figured out where I live! (hint - two foot sign next to door with street numbers). I got the LiPo batteries they lost earlier in the week, plus a roll of nichrome for making igniters. I'm now missing the connectors for these batteries; they lost these, too. When Amazon sends you a notice of delivery, frequently, there is a little "blurb" about re-ordering. If I order about anything now, the expected delivery is close to Jan. 1. Nope, I'll wait, buy locally, or do without.
 

jqavins

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Do you object to me calling a "ball on a stick" a tool? :p
Not a bit. For getting the same profile no matter the tool angle there's nothing better than a sphere; come to think of it, there's nothing else. I was just taking a guess.
I have a theory that I am testing out.
Good!
I believe that we use wayyyyyyyyyy too much epoxy on average to complete a build. I am trying to build a skills and tool kit to calculate and apply the "right" fillet in every circumstance, based on purpose, position, visibility, supporting bonds, et al.
Yes, you're probably right, with one big caveat.
And in the case of external fin fillets.... too much emphasis on aesthetics as a priority over aerodynamic and structural concerns. Aesthetics, IMO, should reveal themselves from elegant engineering and skillful production/construction.
But emphasize that where concede it's your opinion. If someone else likes the look of big fillets and prioritizes them over performance, it's not for any of use to say they're putting "too much" emphasis on it.

Also, I bet there is no single optimum, even disregarding aesthetics. I read of a study long ago by the MIT rocket society of the fillet size that gives the lowest drag, and I was very surprised by how small that is. I just bet it's so small that the strength of the joint is increased substantially by some further increase (though I can't prove it). And what is "substantial" is another matter of opinion, as it's undoubtedly a case of diminishing returns. So if you've got hard landings to consider, you likely get into a trade-off between strength on one hand and flight performance on the other. And for that, if I'm right, there is no well defined figure of merit that can be maximized because the optimum compromise is, once again, a matter of opinion and preference.

Sorry, that drifted a long way from "ball on a stick".
 

cautery

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Not a bit. For getting the same profile no matter the tool angle there's nothing better than a sphere; come to think of it, there's nothing else. I was just taking a guess.

Good!

Yes, you're probably right, with one big caveat.

But emphasize that where concede it's your opinion. If someone else likes the look of big fillets and prioritizes them over performance, it's not for any of use to say they're putting "too much" emphasis on it.

Also, I bet there is no single optimum, even disregarding aesthetics. I read of a study long ago by the MIT rocket society of the fillet size that gives the lowest drag, and I was very surprised by how small that is. I just bet it's so small that the strength of the joint is increased substantially by some further increase (though I can't prove it). And what is "substantial" is another matter of opinion, as it's undoubtedly a case of diminishing returns. So if you've got hard landings to consider, you likely get into a trade-off between strength on one hand and flight performance on the other. And for that, if I'm right, there is no well defined figure of merit that can be maximized because the optimum compromise is, once again, a matter of opinion and preference.

Sorry, that drifted a long way from "ball on a stick".

Yes, of course. Pretty much everything I say/write is my opinion. I try to create them with a strong factual base.... but sans mathematical/experimental proofs, which I am mostly not gonna do, they remain opinions. ;)

I've read similar positions on the topic to that MIT study. And had many conversations about it with fixed-wing maintenance and engineering pilots back when I was still a rotary-wing maintenance officer and test pilot.

LMAO! Yeah, wrong thread to drift. Frankly, when I wrote my post above, I mistakenly thought we were in a different thread... brain slipped a tooth. :)
Feel free to PM me if you want to continue the discussion or post in my build thread... :D

Be well! :)
 

Doug Holverson

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I took some pictures and playing catch-up here.

From warmer days: I forgot to take water and batteries out to the field once. I got some Day-Glo stickers and made these, inspired by the old AVI Astroport stickers from the middle '70s.
stickers.jpg

I finished the Strato-Blaster a while back and I'm waiting for next flying season.

hummingblaster1.jpg

hummingblaster2.jpg

I epoxied the wings together for the Skydancer.

skydancerwing.jpg

And after that set up. I test fitted things together just to see how they look.

sktdancertestfit.jpg

Here are recreations of the MIT Hawk and Stars&Stripes with a Bogling in progress.

mitrcbgs.jpg

These are 3D printed razor-planes of my own creation. These take razor blades which are cheaper, shaper, and much more common then the version in the hobby shops. I printed them in nostalgic '70s patriotic colors like Bicentennial and Allis-Chalmers....

razorplanes.jpg

I need to upload the files to Thingiverse someday.
 

jqavins

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No need; the very purpose if spackle is to be applied, sanded smooth, and then painted. I use a light weight foamed spackle with primer built in. It goes on like cake frosting. It is weak and soft, so it's only for aesthetic use, like filling grain or oversize fillets.
1670621002065.png
 

cautery

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No need; the very purpose if spackle is to be applied, sanded smooth, and then painted. I use a light weight foamed spackle with primer built in. It goes on like cake frosting. It is weak and soft, so it's only for aesthetic use, like filling grain or oversize fillets.
View attachment 550121
Sounds light (lighter than Bondo), relatively resistant to heat, and more likely I will use the remainder on something else...

Screenshot 2022-12-09 162758.jpg
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
Reckon it would serve to fill the depression in an epoxy-filled drill hole some moron put in the wrong place on an air frame? ;)
 
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Doug Holverson

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Update on the Bogling: the wings are foiled and ribbed and the tips are glued on to dry overnight.

bogling.jpg

I'm about rocketed out for today. Maybe I'll go draw some nekomimi with bakunyuu... Or something....
 
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Lugnut56

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Sorry it took so long to get this posted, but my son is visiting from out of town. This is file still needs some fine tuning as I was going to set the mass, CG and verify the dimensions after building my kit. Also, Rocksim doesn't want to run a simulation I think because I had to use the "pod" feature to build this (I've had issues with other designs that incorporate "pods"--sometimes Rocksim will run a simulation ok, other times just says n/a or nan.)
 

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No need; the very purpose if spackle is to be applied, sanded smooth, and then painted. I use a light weight foamed spackle with primer built in. It goes on like cake frosting. It is weak and soft, so it's only for aesthetic use, like filling grain or oversize fillets.
View attachment 550121
exactly+1 ,purely cosmetic to make the surfaces smoother than a newborns bottom. Now I'm wondering if the 3M product you pictured is smoother/buttery than the DAP spackling compound? The reason I'm abandoning the Bondo Spot/Glazing product is simply health related, as it swells my eyes 1/2 shut. :mad: These water-based fillers also sand so easily.👍
 
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I finished the fill/sanding process on the maxi Alpha. Now I have to wait on warmer temps before spraying on primer.
Then I have to choose the colors, as I'm not going back to stock.
 
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Tech 68

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Used the phone app to run the GoPro Hero 5 Session that will be looking out the side of my Level 3 rocket.
Been fairly intimidated by it, mostly since I really didn't understand it. Got it to take video until the battery ran out, a little over an hour. Shut down on it's own, and saved all the files, so I should be good for the flight.
 

StreuB1

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Ground out half of the 1/2" JB weld fillets on one of the fins on my Mach 2 for repair. Sat on it at MWP and didn't think I hurt it. Then flew it to 14k and upon recovery I realized that the fin was half cracked!

Sanded the joints, let some thin CA wick into the fin to airframe joint, let it dry, sand it, then reapplied new JB weld fillets. Curing in the basement now.

Filled some crap primer wrinkle/cracks in the vent band of my 5" Super Jart and did some sanding.

Working on some design work for my Balls projects. Designed an HEI closure for the AT 75mm hardware. Designed a tail cone for the AT 98mm hardware. Began working on the interstage design and came up with a novel fin attachment and reinforcement scheme.

Sat on my arse and watched a lot of YouTube as well.

Had the day off so it was semi-productive.
 

tsmith1315

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Went to an estate sale after dropping our son off at school for finals.

There's an 8" sonotube sitting in the carport for $2, probably 48" long. Like I need another project, but it was not possible to pass on that for 2 bucks. Now, what to make of it?
 

StreuB1

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Went to an estate sale after dropping our son off at school for finals.

There's an 8" sonotube sitting in the carport for $2, probably 48" long. Like I need another project, but it was not possible to pass on that for 2 bucks. Now, what to make of it?

Why an 8" Fat Boy of course!!!!

FYI to all out there. Seeing a sonotube at a garage sale or on the curb is an immediate sign and you must pick it up and build something with it.
 

teepot

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I'm telling you guys. Try the GoodFila stuff. It's perfect. Smooth like butter, thins quickly without lumps, dries fast and easy to sand. I smear it on the whole tube with gloved hands. Then sand the whole thing. No peaks and valleys.
And I'm still waiting on parts for the next rocket.
 
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