I don't see why not--they stayed on right?!
Well, yes, there is that . . . LOL !
Dave F.
I don't see why not--they stayed on right?!
This is what we DO NOT want Chuck's fins to do !
Dave F.
I’m thinking the Nike Smoke fin can from Binder Design is going to be solid for whatever we throw at it.
It is interesting to watch when rockets lose fins. It ain’t cheap going the aluminum route but there’s a peace of mind doing it this way.
Chuck C.
That looks more like the effect of a spinning item with a “rolling shutter” camera device:
Don’t get me wrong, there would have to be *some* flutter in the fins to cause it, my point is more that the rolling shutter makes the video hard to analyse for an understanding of just how much.
Another interesting flutter video . . . Note the difference.
Dave F.
If you're going the stringer route, you might want to use poplar....you can get clear grain 1x2 x10' at Menards for $8 each.....It's impressive the amount of internal structure needed to handle the boost of 5000 lbs of thrust.
In my rockets before this the airframe alone could handle the boost with the centering rings only keeping the motor centered (for the most part).
Now a lot of thought has to be put into not allowing the airframe to fold under pressure. And that comes from internal stringers and ribs.
As parts start coming in it won't be long before the build begins in earnest.
Am getting a handle on making CR's that fit really well into the airframe. Those are the ribs.
Rather than one long metal stringer am now going to insert (8) 1 3/4" birch stringers between each of the CR's from the bottom of the rocket to the altimeter bay. Everything on the inside will be glassed. Every CR and stringer.
This allows the thrust to be transferred to not only the bottom of the airframe but also through the CR's, stringers and the motor itself which will have a thrust plate at it's upper enclosure.
The goal is to build a rocket that can be flown (and recovered) several times.
It's a daunting project and certainly the biggest I've ever done. Couldn't do it without the ideas of you folks here and others with real-world experience in building big rockets.
Chuck C.
If you're going the stringer route, you might want to use poplar....you can get clear grain 1x2 x10' at Menards for $8 each.....
It's impressive the amount of internal structure needed to handle the boost of 5000 lbs of thrust.
In my rockets before this the airframe alone could handle the boost with the centering rings only keeping the motor centered (for the most part).
Now a lot of thought has to be put into not allowing the airframe to fold under pressure. And that comes from internal stringers and ribs.
As parts start coming in it won't be long before the build begins in earnest.
Am getting a handle on making CR's that fit really well into the airframe. Those are the ribs.
Rather than one long metal stringer am now going to insert (8) 1 3/4" birch stringers between each of the CR's from the bottom of the rocket to the altimeter bay. Everything on the inside will be glassed. Every CR and stringer.
This allows the thrust to be transferred to not only the bottom of the airframe but also through the CR's, stringers and the motor itself which will have a thrust plate at it's upper enclosure.
The goal is to build a rocket that can be flown (and recovered) several times.
It's a daunting project and certainly the biggest I've ever done. Couldn't do it without the ideas of you folks here and others with real-world experience in building big rockets.
Chuck C.
It's lighter, easy to work with, clear grain, reasonably strong and readily availableWhy poplar over birch? Because it's pre-cut?
Thanks.
Chuck C.
Chuck,
I found some interesting data for the "OuR" project . . .
https://rasaero.com/dloads/OuR Project R Rocket.pdf
Dave F.
View attachment 371585
Why poplar over birch? Because it's pre-cut?
Thanks.
Chuck C.
Thanks for posting that Dave, Phil Prior was my TAP.... great guy! .may he.rest in peace......their project deserves to be rememberedChuck,
I found some interesting data for the "OuR" project . . .
https://rasaero.com/dloads/OuR Project R Rocket.pdf
Dave F.
View attachment 371585
Chuck,
I found some interesting data for the "OuR" project . . .
https://rasaero.com/dloads/OuR Project R Rocket.pdf
Dave F.
View attachment 371585
From a structural point of view:
-How thick are the 12" tube walls?
-Does anyone have stress data for G12 tubing? (yes, I tried the search function)
12" diam w/ 1/8" wall is ~2.34 in^2 of area which means 9000 lbs subjects it to ~3.85 ksi of pure compression stress. Bending or lateral forces will make that worse, but that's not a terrible number from a material standpoint.
Yes you're right it does great with the compression.
It's things like windshear at Mach 2+ that makes us want to give it a good internal structure.
Kind of like an airplane where the skin is just for aerodynamics. It's the ribs and stringers that give it the strength.
Thoughts?
Chuck C.
...[/QUOTE]I couldn't find any data on filament wound tube either...flat plate G-10 or HT seems to be high, 55-60k flat loading or 35k edge loading but I'm going to guess filament wound tube is less than edge loaded plate...still.....you have to remember that built correctly the whole structure will be much stronger than any individual componentFrom a structural point of view:
-How thick are the 12" tube walls?
-Does anyone have stress data for G12 tubing? (yes, I tried the search function)
12" diam w/ 1/8" wall is ~2.34 in^2 of area which means 9000 lbs subjects it to ~3.85 ksi of pure compression stress. Bending or lateral forces will make that worse, but that's not a terrible number from a material standpoint.
I couldn't find any data on filament wound tube either...flat plate G-10 or HT seems to be high, 55-60k flat loading or 35k edge loading but I'm going to guess filament wound tube is less than edge loaded plate...still.....you have to remember that built correctly the whole structure will be much stronger than any individual component[/QUOTE]
I couldn't find any data on filament wound tube either...flat plate G-10 or HT seems to be high, 55-60k flat loading or 35k edge loading but I'm going to guess filament wound tube is less than edge loaded plate...still.....you have to remember that built correctly the whole structure will be much stronger than any individual component.
Chuck C.
I couldn't find any data on filament wound tube either...flat plate G-10 or HT seems to be high, 55-60k flat loading or 35k edge loading but I'm going to guess filament wound tube is less than edge loaded plate...still.....you have to remember that built correctly the whole structure will be much stronger than any individual component
That's a tough one, one option that came to mind is to epoxy a coupler inside the booster body tube to double it....then take another coupler and coat the inside with mold release and do a hand layup using the coupler as a mold....remove the coupler/mold and the piece you've laid up should slide into the booster.... .you'd have to double the payload section where the " new coupler" gets glued in as well.....just a thought
Chuck,
Here is data on Filament-Wound Tubing & More . . . ( I want a "raise" . . . I'm worth at least twice what you're paying me - LOL ! )
I very STRONGLY suggest that anyone reading this thread take note of the data on the archived website below !
Dave F.
https://web.archive.org/web/2015021...aterials.org/datastore/tubes/Axial/index.html
https://web.archive.org/web/2014121...terials.org:80/datastore/fins/Bend/index.html
https://web.archive.org/web/20141128034806/https://rocketmaterials.org:80/datastore/cord/index.html
https://web.archive.org/web/2012072...tmaterials.org/research/metallurgy/index.html
https://web.archive.org/web/2015021...ls.org:80/datastore/cord/Shear_Pins/index.php
https://web.archive.org/web/2014120...rials.org:80/datastore/fins/Tension/index.php
https://web.archive.org/web/20141205010845/https://www.rocketmaterials.org:80/datastore/index.html
https://web.archive.org/web/2015021...org/datastore/hardware/Quick_Links/index.html
https://web.archive.org/web/20150217105515/https://rocketmaterials.org/testing/index.html
https://web.archive.org/web/20080821120644/https://www.spacewarptechnology.com/SWT/High Altitude Tests/TABLE_CONTNETS.htm
View attachment 371614
Chuck,
a relatively simple way to make the problem easier is to transmit thrust to the airframe at the head end. Everything below the top of the case is then in tension, which is pretty straightforward to estimate and manage [threaded rod, cables, kevlar rope have all been flown successfully at these loads]. Buckling concerns go away for that length of the airframe. The coupler necessary to take the thrust is easy to calculate: Compressive strength of generic fiberglass is about 10ksi. Shear strength of epoxy is about 1ksi in practice [5ksi strength bonds are not necessarily as easy to realize as one might think based on the data sheet]. In industry we use 1ksi for bond strength unless there is test data. Plywood bulkheads will compress a little, but can't really fail if well supported. High layer count birch plywood barely moves. Plain exterior grade sanded-one-side plywood has been fine to. The design goal is everything solid above the thrust point is loaded in compression and every bond joint is loaded in shear with adequate margin on bond surface area [e.g. 2x]. This has worked well on several rockets in this thrust regime.
I am sad to see that rocketmaterials.org is gone, a very good site it was.
Regardless of where thrust is applied, buckling is the failure that is more challenging to predict without characterizing the tube first before designing the rocket. Tube buckling realistically has to be tested at full scale to be valid because of material property uncertainties. Stringers will work but may be hard to optimize. Sandwich construction is very friendly for buckling concerns
br/
Tony
Great research there Dave.
That is some awesome reading. Lots of fun homework!
Chuck C.
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