Quantcast

2.63" (formerly 3" Mailing) Tube Printed Rocket

The Rocketry Forum

Help Support The Rocketry Forum:

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
True enough... and yeah, I think its too flexible.

I used a profile generator tool for the NACA based shapes in OnShape.
 

BDB

Absent Minded Professor
Joined
Aug 22, 2015
Messages
2,184
Reaction score
416
It’s good to know I’m not the only one printing fins with too much flex. I changed to NylonX to try to fix the issue—still too flexible in my opinion.
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Yeah, haven't tried NylonX yet... not sure my printer can handle it based on recommended temps.

I did just do another test print (well thats what I call it since I got a dimension wrong) where I printed with the layers parallel to the root chord. Came out really well.

I also switched from the NACA M1 to the M2 shape, so its a tad thicker.

Its definitely much more rigid

PXL_20210129_122526617.jpg
 
  • Like
Reactions: BDB

Dustin Lobner

Well-Known Member
TRF Supporter
Joined
Sep 3, 2019
Messages
359
Reaction score
202
That works! Can you put a big fillet at the base of it? My 3D printed fins are usually 10mm wide at the base, 5mm at the tip, and at LEAST a 10mm radius fillet at the root, so it's more like 30mm wide at the root. They come out stiffer than the .093" G10 fins I had on my L2 rocket.
 

Nytrunner

Pop lugs, not drugs
TRF Supporter
Joined
Oct 15, 2016
Messages
7,751
Reaction score
3,377
Location
Huntsville AL
That leading edge layer print looks good. The ribs can be puttied or epoxy filled and sanded for smoothness.

How fast is this going to go?
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Well, that did not go well. Layer shift, had same thing happen on my first attempt at this. Upright and second shorter span attempts didn't layer shift. So something about when its moving to the edges of the x-axis - also apparently came unstuck. Might try it at along the z-axis.
 

Attachments

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Ah, yeah, I think this one is like 8mm at the base/mount joint. Looks like its only a 5mm filet.

Thankfully its mostly parameter driven, so I can adjust the model pretty easily.

That works! Can you put a big fillet at the base of it? My 3D printed fins are usually 10mm wide at the base, 5mm at the tip, and at LEAST a 10mm radius fillet at the root, so it's more like 30mm wide at the root. They come out stiffer than the .093" G10 fins I had on my L2 rocket.
 

Dustin Lobner

Well-Known Member
TRF Supporter
Joined
Sep 3, 2019
Messages
359
Reaction score
202
Yuck.

....might be interesting to fly with the layer shift, lol. Get them all set up the same way and see what kind of spiral you get.
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
That leading edge layer print looks good. The ribs can be puttied or epoxy filled and sanded for smoothness.

How fast is this going to go?
No idea... figure its gonna have a high quotient of drag, kinda heavy. Shooting for Gs and Hs. So prelim sim model says around ~500ft/s^2 with a H128
 

Nytrunner

Pop lugs, not drugs
TRF Supporter
Joined
Oct 15, 2016
Messages
7,751
Reaction score
3,377
Location
Huntsville AL
No idea... figure its gonna have a high quotient of drag, kinda heavy. Shooting for Gs and Hs. So prelim sim model says around ~500ft/s^2 with a H128
That's not bad at all. Should see minimal aero deflection.

Ground hit forces will likely be your issue. Bring it down soft!
 

Dustin Lobner

Well-Known Member
TRF Supporter
Joined
Sep 3, 2019
Messages
359
Reaction score
202
I've never had issues with 3D printed fins snapping on impact, but what I do is print a decently sized tail cone that also does motor retention. I had one come down on a rock....took a bite out of the tail cone, but the fins were fine.
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
And I "borrowed" Dustin's idea with the tail cone/motor retention too. :) 'sides if a fin break, print another one, unbolt the broken one, bolt in new one - fly again!
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Well, worked.... Shot is a little weird, certainly not as grainy the lighting seem to make it. Pretty darn stiff, certainly can't flex it like could with the layers following the root.

PXL_20210130_043529764.jpg
PXL_20210130_043542627.jpg
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Weights in at 1.56 ounces... chunky
 

Dustin Lobner

Well-Known Member
TRF Supporter
Joined
Sep 3, 2019
Messages
359
Reaction score
202
Do you do any root to tip taper as well? I can't really tell...
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Yeah, its slight... 2mm difference.
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Decided to scale down slightly to a LOC 2.63" due to overall weight and wanting to meet certain performance envelope parameters (min. 50f/s off a 72" rail, between 1000-3000', and from G to I motors) due to field sizes, etc.

The motor and fin mount.

PXL_20210203_140119961.jpg


And a shot with a fin.

PXL_20210203_140133082.jpg
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Screenshots from OpenRocket

Capture.PNG


And the performance simulations...

Capture2.PNG


These may change as I had to approximate the weight of the nose cone.

Technically I have about 84" on the rail with the rail button being where it is, so speeds coming off my rail will be a tad higher. I prefer to shoot lower because if I launch at other events that have existing rails then that becomes an issue. It does impact motor selection a bit too, i.e. on shorter rails the Gs may be out.
 
  • Like
Reactions: BDB

BDB

Absent Minded Professor
Joined
Aug 22, 2015
Messages
2,184
Reaction score
416
This looks great! I really like method for fin mounting. My design for something similar is much more complex.

Do you have any tricks for knowing where to drill the holes for fin attachment through the airframe besides "measure really carefully?"
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Thanks. Plan is to print a guide. Although I've also been trying to see how I can roll this out so I can just print it on paper as a wrap; haven't figured that one out.

Capture.PNG


Here is the Onshape link... its constantly changing, so mileage may vary. :) And its public, so it can be used in the "free" OnShape version (which is what I use).

https://cad.onshape.com/documents/9...c62a6c867bece3d11f/e/dd0909b35cc525e5032c1046

I'm sure someone who is CAD expert could probably put these together much more efficiently, etc. but they are working for me now as a neophyte.
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Hard to see, but I was able to figure out (with planes and geometry) how to angle the attachment holes so that they are perpendicular to the curved surface. Other than better sitting on the fit attachment without needing to flatten areas, it also should mean there is some more mechanical 'grip' as the bolts are angled in.

Capture.PNG
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Printed out motor mount, after some adjustments, prints, readjustments, etc. Decided to go with 3mm screw hardware; think it should be sufficient.

PXL_20210214_141750218.jpg


Checking the inserts that they fit, align, etc.

PXL_20210214_141759969.jpg


Applied some heat with a specific 3mm soldering tip for inserts. Turns out ok, but definitely have to pay attention as there really is no 'redo'

PXL_20210214_145925606.MP.jpg
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Made some more progress.. was able to get a drill hole guide printed.

PXL_20210215_164120610.jpg


Then it all lined up as it got tied down with 3mm bolts.

PXL_20210215_164514251.jpg

PXL_20210215_164506626.jpg


From the top
PXL_20210215_164535246.jpg


Now to get the other two fins printed, the brass inserts inserted, so the fins then can be mounted.
 

Nytrunner

Pop lugs, not drugs
TRF Supporter
Joined
Oct 15, 2016
Messages
7,751
Reaction score
3,377
Location
Huntsville AL
It's a real neat fin asssembly unit you've made. Trades extra mass for assembly and storage ease
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Yeah, thats what it kinda turned into.... its been an interesting journey. :)
 

thzero

Well-Known Member
TRF Supporter
Joined
Jun 5, 2018
Messages
168
Reaction score
107
Have plans to just print the attachment blocks, and use plywood or fiberglass plates for the actual fins. This would work a bit different in that there would be a tab that would go through the tube into the motor mount, then the attachments mounts would be screwed into the fin and through the body tube to the motor mount.

Not really sure its a great replacement for just epoxing the fins in, but hey... no fun to only build rockets just one way!
 
Top