So I've been struggling with how to keep leading edges and tip to tip reinforcements intact during high speed (M2.7+) flights. Mach 3.7 in this particular project. I've been doing lots of combing through threads here, a flight or two of my own that illustrated what not to do, and some laying awake at night pondering.
I finally decided that I really liked someone else's idea, including what they learned, and what they would do differently. I am shamelessly stealing A5tr0 An0n's method outlined in this post and the thread that led up to it-
https://www.rocketryforum.com/threa...ase-67kft-msl-m3-5.142693/page-5#post-1776969
So my fins start with a high temperature core, and are one piece, rather than a separate leading edge. In this case it's Garolite G-11, just like in his thread. As illustrated in the link above, the tip to tip reinforcement sits in a pocket machined into the face of the fin. This project started by modelling the fin in Fusion 360.
This pocket, plus the bevels, made for some complex machining requirements. Thanks to a very talented co-worker, I have four fins that are straight-up rocket art.
Because of that curve in the corner of the pocket, it occurred to me that it would be nice to have a very precise and accurate shape for the tip to tip reinforcement. Having a nice clean edge at the border of the pocket would help making sure it stays in place. Plus better aesthetics and style points, right?
More pondering and laying awake happened. I finally decided that I might be able to cut the carbon fiber on our Cricut Maker. The Maker has a cutting wheel attachment that is similar to what I'd be using to cut it anyway. It's also capable of adding quite a bit of pressure to the wheel.
This method wouldn't work for all carbon fiber, as it has to be stuck down to a carrier sheet to be cut, then peeled off after the cutting is complete. Regular carbon fiber would come off in shreds. But some of the newer, more modern products come on a carrier of their own. Some of the Hexcel spread tow products that are becoming more popular would be a good candidate. In this case I'll be using unidirectional prepreg that comes stuck to it's own carrier paper. Due to this fact, I peel the carbon fiber and it's carrier off the Cricut carrier sheet in one piece.
So next I modeled the whole thing in Fusion. I used the sheet metal tool to simulate the carbon fiber in order to be able to convert it to a flat pattern. I'm pretty new to Fusion still, so a big thanks to Bob Heninger for helping me figure the sheet metal part out. The flat pattern can be exported as a .DXF file, which can be imported into the Cricut Design Space software. Here's a few pics of that process.
The other issue that keeps me up at night is that none of this is going to work at all if the fins aren't on exactly straight or if the fillets aren't exactly the radius (.25") that was specified in Fusion. I'll elaborate on how I'm trying to control that in my next post. The jury is still out as to whether I was successful in this regard or not. All this extra work might be for not. But still fun.
I finally decided that I really liked someone else's idea, including what they learned, and what they would do differently. I am shamelessly stealing A5tr0 An0n's method outlined in this post and the thread that led up to it-
https://www.rocketryforum.com/threa...ase-67kft-msl-m3-5.142693/page-5#post-1776969
So my fins start with a high temperature core, and are one piece, rather than a separate leading edge. In this case it's Garolite G-11, just like in his thread. As illustrated in the link above, the tip to tip reinforcement sits in a pocket machined into the face of the fin. This project started by modelling the fin in Fusion 360.
This pocket, plus the bevels, made for some complex machining requirements. Thanks to a very talented co-worker, I have four fins that are straight-up rocket art.
Because of that curve in the corner of the pocket, it occurred to me that it would be nice to have a very precise and accurate shape for the tip to tip reinforcement. Having a nice clean edge at the border of the pocket would help making sure it stays in place. Plus better aesthetics and style points, right?
More pondering and laying awake happened. I finally decided that I might be able to cut the carbon fiber on our Cricut Maker. The Maker has a cutting wheel attachment that is similar to what I'd be using to cut it anyway. It's also capable of adding quite a bit of pressure to the wheel.
This method wouldn't work for all carbon fiber, as it has to be stuck down to a carrier sheet to be cut, then peeled off after the cutting is complete. Regular carbon fiber would come off in shreds. But some of the newer, more modern products come on a carrier of their own. Some of the Hexcel spread tow products that are becoming more popular would be a good candidate. In this case I'll be using unidirectional prepreg that comes stuck to it's own carrier paper. Due to this fact, I peel the carbon fiber and it's carrier off the Cricut carrier sheet in one piece.
So next I modeled the whole thing in Fusion. I used the sheet metal tool to simulate the carbon fiber in order to be able to convert it to a flat pattern. I'm pretty new to Fusion still, so a big thanks to Bob Heninger for helping me figure the sheet metal part out. The flat pattern can be exported as a .DXF file, which can be imported into the Cricut Design Space software. Here's a few pics of that process.
The other issue that keeps me up at night is that none of this is going to work at all if the fins aren't on exactly straight or if the fillets aren't exactly the radius (.25") that was specified in Fusion. I'll elaborate on how I'm trying to control that in my next post. The jury is still out as to whether I was successful in this regard or not. All this extra work might be for not. But still fun.