Low mass, high drag designs?

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I love the Mellows :) F15 and G33 work great in the Mega Mosquito. LOC makes kits for the long burns. I've flown my LOC High tech H45 on the H53 and I55 Mellows. My EZI-65 has flown on the J94. I'm waiting for a calm day to fly my Motoreater (similar to LOC Magnum but with 9 motor mounts) on the L265 :grin: Haven't decided what to fly the J150 in yet :grin:
 
I've found tube fin rockets don't weathercock although in very high winds they tend to 'crab' with the wind.
 
EXPjawa said:
In addition to tube fins, ring tails have extremely high drag. I've done a couple designs with concentric ring tails. One which is a 3 oz model that (according to the sim) would require an F32 to break 700 feet. An E9 pushes it to about 525' or so.
Click to expand...

Can I assume you mean in Rocksim? OR doesn't seem to pay much attention to ring tails as far as its sims go.

On the other hand, I was not aware that ring tails had that much drag, given that they usually are short. Maybe it was the 3 concentric ones that did it?
 
Yes, using Rocksim. A single ring tail will induce quite a bit of drag, for reasons similar to why tube fins do. You're sort of forcing air flow through a hole, rather than allowing to slide by a normal fin. That is, over of course, oversimplified. It would seem in just playing around with the model that shorter ring tails have higher margins than longer ones. By that, I mean that the drag appears higher when they're shorter, although the apparent effect could be due to the increase in ring mass as it gets longer...
 
For a low mass high drag rocket you could start out with the infamous Sunward Umbrella kit. That one is always good for a laugh from the high power guys. Not so good to boost your macho image if you are seen carrying one to the pad. It needs some power to get going, but a long burn curve would be nice, and the shortest delay possible to deploy a recovery system just for looks. A cut down blackjack F12-4 to a 2 to 3 is nice, but don't tell anyone you are messing with a 4 delay! The RSO will be kind since it is a real kit (not scratch built) and does not have pods.:)
 
Rocketjunkie said:
I love the Mellows :) F15 and G33 work great.....
Click to expand...

F15? I just got all excited to find a 'smaller' Mellow, but I'm not finding that.

On a side note, it kinda cracks me up that the F30 WLB is 2.4 seconds? Doesn't seem like a long burn to me.

If somebody could school me on a legal way to use shave down an AT G12RC to fit a 29/40-120 case...

8.51 seconds?! Now -that's- a looong burn!!
 
The old Estes Executioner on an AT 24/40 F12 fell into that category. Real nice slow boost, not a lot of coast.
 
You may want to look into foam. burkefj over in the glider section has been building lightweight rockets out of Depron (https://www.rocketryforum.com/showthread.php?119772-X-20-Dyna-Soar-with-titan-booster). You can use foamboard for fins. I've been thinking about hot-wire-cutting a relatively fat fuselage (say 5.5") the same way I have wing cores cut for my RCRGs. I think I can get a LOC Magnum size rocket to fly at Moffett if I do that.

Ari.
 
iter said:
You may want to look into foam. burkefj over in the glider section has been building lightweight rockets out of Depron (https://www.rocketryforum.com/showthread.php?119772-X-20-Dyna-Soar-with-titan-booster). You can use foamboard for fins. I've been thinking about hot-wire-cutting a relatively fat fuselage (say 5.5") the same way I have wing cores cut for my RCRGs. I think I can get a LOC Magnum size rocket to fly at Moffett if I do that.

Ari.
Click to expand...

Thanks, Ari. I just checked out the link, and this is a really interesting technique. He makes some HUGE lightweight rockets that way. Depron is the material you use for your gliders? Do you have a good source for that locally? I've seen regular foam core at several local stores, but the thin 2mm material he uses for the skins looks like a specialty product.
 
Tube finned, large OD main tube. Like a "big daddy super neon XL". Should come in pretty light (SNXL is about 6.5 OZ) and stay low.
 
I can find depron locally in 2mm, 3mm and 6mm, but you can get it from rcfoam.com Shipping will be expensive for one or two sheets...but you can also try using dollar tree foam for centering rings and stringers, maybe remove the cardboard skin, and use cardstock for skins for example as alternatives... I've found that in these larger diameters, 8" and up they don't really carry much mass relative to their size so they bleed off speed after burnout pretty quickly....they almost never arc over, they just keep vertical, then backslide till ejection. I think Ari is proposing hot cutting a solid foam fuse/tube, maybe cut internally for a stuffer tube instead of doing a built up structure, should be feasable...

Here is a video

[video=youtube;r__SLcpDChU]https://www.youtube.com/watch?v=r__SLcpDChU[/video]

It's 10" diameter and 6.5 pounds ready to fly, you can see how quickly it bleeds off speed after burnout...
 
AeroMicro in Santa Clara sells Depron sheets. I'm sure other local hobby stores do as well. I forget where you live in the Bay.

Ari.
 
swatkat said:
Tube finned, large OD main tube. Like a "big daddy super neon XL". Should come in pretty light (SNXL is about 6.5 OZ) and stay low.
Click to expand...

That would definitely fit the bill for a high-drag design. Thanks for the suggestion. I'm going to try to come up with a traditional fin design if I can.
 
burkefj said:
I can find depron locally in 2mm, 3mm and 6mm, but you can get it from rcfoam.com Shipping will be expensive for one or two sheets...but you can also try using dollar tree foam for centering rings and stringers, maybe remove the cardboard skin, and use cardstock for skins for example as alternatives... I've found that in these larger diameters, 8" and up they don't really carry much mass relative to their size so they bleed off speed after burnout pretty quickly....they almost never arc over, they just keep vertical, then backslide till ejection. I think Ari is proposing hot cutting a solid foam fuse/tube, maybe cut internally for a stuffer tube instead of doing a built up structure, should be feasable...

Here is a video

[video=youtube;r__SLcpDChU]https://www.youtube.com/watch?v=r__SLcpDChU[/video]

It's 10" diameter and 6.5 pounds ready to fly, you can see how quickly it bleeds off speed after burnout...
Click to expand...

That video is great! That is more or less the flight profile I'm looking for, and the size is amazing. Thanks for posting. I also checked out some of your other builds too, and they are all really interesting.

I'm thinking for the first try, maybe I will just use the cheapo foam core and a card stock skin. I'm also going to go for a very simple rocket design --- nothing too detailed.

What adhesives do you use for foam and for foam to paper bonds?
 
Daddyisabar said:
For a low mass high drag rocket you could start out with the infamous Sunward Umbrella kit. That one is always good for a laugh from the high power guys. Not so good to boost your macho image if you are seen carrying one to the pad. It needs some power to get going, but a long burn curve would be nice, and the shortest delay possible to deploy a recovery system just for looks. A cut down blackjack F12-4 to a 2 to 3 is nice, but don't tell anyone you are messing with a 4 delay! The RSO will be kind since it is a real kit (not scratch built) and does not have pods.:)
Click to expand...

Ever since I saw Mary Poppins, I've been terrified of umbrellas.
 
iter said:
I think I can get a LOC Magnum size rocket to fly at Moffett if I do that.

Ari.
Click to expand...

That would be so fun! I alway feel like a big fish in a small pond flying something the size of a G-Force at Moffett. A 5.5" rocket over 6' tall flying on a G motor would be amazing!
 
ThirstyBarbarian said:
Ever since I saw Mary Poppins, I've been terrified of umbrellas.
Click to expand...

On a D12-3 you will get a slow and terrifying flight profile. You have to be "Practically Perfect in Every Way" to make it work. An inverted chimney sweep brush would do the trick on a big smokey or blackjack motor. If it is windy you can just go fly a kite.
 
For the skin I use 3m-77 spray contact cement. For foam to stuffer tube or foam to foam internal structure I use foam safe CA+ either bob smith gold or hot stuff UFO thick.

Frank


ThirstyBarbarian said:
That video is great! That is more or less the flight profile I'm looking for, and the size is amazing. Thanks for posting. I also checked out some of your other builds too, and they are all really interesting.



I'm thinking for the first try, maybe I will just use the cheapo foam core and a card stock skin. I'm also going to go for a very simple rocket design --- nothing too detailed.

What adhesives do you use for foam and for foam to paper bonds?
Click to expand...
 
I went to Hobby Lobby today, and they had these HUGE plastic Easter eggs. I'll post a pic later, but I'll describe it now. It's a set of three plastic eggs nested inside each other. They open into two pieces, one elliptical, and one almost hemispherical, just like the little plastic eggs used to hide gifts on Easter, but big. That means there are six parts, each one potentially a lightweight nose cone. I don't have measurements in front of me, but the big egg is about 9.75" in diameter, the middle one is about 7.5", and the small one is about 5.5". I don't recall the weights at all, but I think it was around 8 oz, for the biggest parts (maybe more) to under 3 oz for the small ones. I'll post the accurate details when I post the pics.

The huge nested egg set was usually $20, but on sale for 40% off its $16, for 6 big lightweight NCs. That's a decent deal. I also got a sheet of foam core material and a sheet of card stock. I think with other materials I have laying around, I might be able to put together a rocket now!

I've got a lot going on right now, so I won't guarantee I'll get right to it. But I'm pretty excited about the possibility!
 
The best example of what you're speaking of must be the Harry Spears' Jumping Flaming Spider of Death:

attachment.php


Can't be bothered to rotate it. Yes, the legs are full length pool noodles. I believe it does about 800 feet on a K, but Harry could confirm.
 
ThirstyBarbarian said:
I went to Hobby Lobby today, and they had these HUGE plastic Easter eggs. I'll post a pic later, but I'll describe it now. It's a set of three plastic eggs nested inside each other. They open into two pieces, one elliptical, and one almost hemispherical, just like the little plastic eggs used to hide gifts on Easter, but big. That means there are six parts, each one potentially a lightweight nose cone. I don't have measurements in front of me, but the big egg is about 9.75" in diameter, the middle one is about 7.5", and the small one is about 5.5". I don't recall the weights at all, but I think it was around 8 oz, for the biggest parts (maybe more) to under 3 oz for the small ones. I'll post the accurate details when I post the pics.

The huge nested egg set was usually $20, but on sale for 40% off its $16, for 6 big lightweight NCs. That's a decent deal. I also got a sheet of foam core material and a sheet of card stock. I think with other materials I have laying around, I might be able to put together a rocket now!

I've got a lot going on right now, so I won't guarantee I'll get right to it. But I'm pretty excited about the possibility!
Click to expand...

I tried to fly that small blue Hobby Lobby egg last year and I don't like to talk about it much since it left a permanent mark on my record. That plastic is very hard to glue, very waxy and needs to be really roughed up for epoxy to stick. I gave the other eggs to a friend to use as a nose cone or to put big fins on with a decent single composite motor. Those Hobby Lobby eggs are very dangerous! Good luck!
 
Barkley said:
The best example of what you're speaking of must be the Harry Spears' Jumping Flaming Spider of Death:

attachment.php


Can't be bothered to rotate it. Yes, the legs are full length pool noodles. I believe it does about 800 feet on a K, but Harry could confirm.
Click to expand...

ha ha! That is one scary jumping spider!
 
Daddyisabar said:
I tried to fly that small blue Hobby Lobby egg last year and I don't like to talk about it much since it left a permanent mark on my record. That plastic is very hard to glue, very waxy and needs to be really roughed up for epoxy to stick. I gave the other eggs to a friend to use as a nose cone or to put big fins on with a decent single composite motor. Those Hobby Lobby eggs are very dangerous! Good luck!
Click to expand...

I hope I don't end up with egg on my face.
 
Sounds like the best construction method would be "Thru the Shell" fins with rear ejection for parachute recovery. Perhaps a Mars Lander type design. Extra points for a chicken foot landing pad design.
 
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