Hello all!
I am relatively new to HPR (four flights and an L1 under my belt), and would like some help with the construction of my most recent rocket purchase, a RW Fire Flyer. For those who dont know, its a 2.6in thin-wall fg dual deploy rocket with a 54mm MMT, so this bird is going to soar. However, I am planning on overbuilding it somewhat, as in my four flights, I have trashed two rockets due to deployment issues. Since I am so new, I figured I would share my plans with all you fine folks in order to get your thoughts and ideas, and to make sure I dont make any huge mistakes (its no fun without little ones though!). In return for your help, Ill give you a build thread! Sound fair? Perfect!
So, on to the plan, from top to bottom:
First, the fin can. This is going to be a doozy! There is only about 1/8in between the outer wall of the MMT and the inner wall of the airframe. I have never really done internal fillets (or external ones, for that matter) before, and this doesnt seem like a good situation to learn in. Therefore, I think it would be better to simply Rocketpoxy the fins to the MMT, foam the admittedly small space between fins, and make good external fillets. In detailed steps, heres what I am going to do.
1. Figure out where the forward CR goes on MMT
2. Sand MMT and CR, then epoxy forward CR in place
3. Sand forward CR and inside of airframe, then epoxy forward CR to airframe. Aft CR will be in place for this step, but with tape tabs for easy removal.
4. Sand and line the bottom of the fin tab with lots of epoxy, the stick into fin slot. Repeat for each fin, then slide fin alignment guide in place
5. Foam the spaces between the fins
6. Sand aft CR and airframe, then epoxy in place
7. Sand end of MMT, and JB Weld motor retainer onto end
However, I do have a few questions here. First, I am using an Aeropack motor retainer, and the outside lines up almost perfectly with the airframe, so I would like there to be as small a gap between the two as possible. Is there a good way to find the right place to place the forward CR so that it lines up with the top of fin slot? Secondly, the fin slots are about 3/8in too long for the fin tab. I am planning on having the fins as far forward as possible, so that any force on them gets translated directly into the airframe, is that a good idea? Thirdly, recovery. The CRs are so thin that I dont really want to sand them down to allow the Kevlar to pass under the forward CR. Therefore, I was planning on looping the Kevlar around the MMT above the upper CR and knotting it, then once again, similar to how you would truss a roast, pulling it tight, then liberally applying epoxy. Thoughts on this method? Fourthly, the two part expanding foam. I did a little test a few days ago, and mixed some. The foam is still fairly compressible and hasnt stiffened up much at all, is this normal? Did I not get a good mixture ratio? How long does it normally take to cure? Fifthly, rail button positioning. I havent used thin-wall fiberglass before, how do I get a good mount of the rail buttons? Lastly for this section, epoxy choice. I currently have Rocketpoxy, JB Weld, and some standard Five Minute. The Aeropack retainer wants JB Weld for its heat resistance, is there anywhere else that needs that kind of heat resistance, or will I be ok using Rocketpoxy for everything else?
Next up, the electronics bay:
The basics here are that I am using and Eggfinder TRS as my main, and a Stratologger CF as my backup I have never used the TRS before, so I am planning on doing a couple low and slow flights to learn the GPS side before I do something crazy. I am comfortable using the Stratologger, so no worries there. Additionally, since I am keeping the TRSs antenna inside the ebay, there wont be any allthread rods running the length of the bay. Instead of the standard setup, I have decided to have a single length of Kevlar running from MMT to nosecone, running through the ebay, with knots on either side to keep it in place. This allows me to build the ebay without worrying much about its strength, as the only part of it that will be structural is the fg coupler portion, which will have shear pins holding either end of the airframe on until deployment.
The ebay itself will also be fairly non-standard. Instead of a single plane, the sled will be shaped like an upside down capital T. All electronics and hardware will be mounted to the vertical board, and the horizontal board acts to shield the electronics from any whipping of the Kevlar. Both boards will be swiss cheesed to ensure the pressure is constant in each section, and to ensure that all four pressure holes are in use.
I dont have a step by step plan for this part, because I dont think the order of steps matters much at all, but essentially it will be assemble the two bulkheads, cut the two boards and epoxy them together, then fit all mounting hardware for electronics, then wire it all up.
I also have a romanticized vision of having a Remove Before Flight tag hanging off the side of the rocket, which gets pulled once the rocket is on the pad to arm the ejection charges. I think this can be done on the Stratologger easily, as described in the Stratologger manual. The TRS manual is less clear on how it would be done, would I have the limit switch short the reset pads? The TRS manual makes it seem like the TRS would have to reconnect to the LCD receiver at that point, but I would like to have had the connection between the two made before I leave my table. Is there a way to achieve this?
Also, batteries. I have never used LiPo batteries before, so guidance there would be appreciated. The TRS manual wants a 2S 7.4V LiPo battery with at least 350 mAH. It also mentions something about a C rating of the battery. What do these all mean? Some suggested batteries would be great also!
Lastly, is there a good place to calculate the size of black powder charges I need, and the number of shear pins? I would do tests, but I am bouncing between my parents house and my dorm room, and neither want me to keep black powder or live motors, and I dont have any casings of my own (I use my clubs casings, or single use motors).
At the top comes the nosecone:
The nosecone is going to be a fairly simple, standard nosecone. Ill have an eyebolt to hold it to the Kevlar, some method of holding the airframe to the nosecone shoulder, and a removable bulkhead in the nosecone shoulder. For holding the bulkhead to the shoulder, I was going to epoxy two nuts to opposite sides of the interior wall, then pass bolts through the bulkhead wall to screw into the nuts. This allows me to add nose weight, or other electronics like a screamer, to the nosecone at a later date. Also, I am cognizant of the fact that epoxying the Kevlar to the MMT means the nose cone end is the only way to get the coupler tube onto or off of the Kevlar, so I want this end to be removable.
What are some good ways to attach the upper airframe tube to the nosecone shoulder so that its removable, should I need to access the nosecone, but solid enough that I dont need to worry about it breaking from the ejection charge? Also, how do I ensure that the bolt holes in the bulkhead line up with the epoxied nuts?
Lastly, recovery:
Not too much going on here, Im having the15in drogue in the aft tube, 36in main in upper tube, nomex for each with quick links and swivels. I think my only question here is that OpenRocket is warning me that with large motors (6GXL, etc), the main chute is deploying at high speed. Is 60-75 fps too fast? Its going to end up weighing 4ish pounds empty. Also, am I crazy for doing the single line of Kevlar thing? Ive never seen it done, on here or irl.
Sorry for the wall of text, there will be pretty pictures to come, I promise!
Thank you all in advance!
I am relatively new to HPR (four flights and an L1 under my belt), and would like some help with the construction of my most recent rocket purchase, a RW Fire Flyer. For those who dont know, its a 2.6in thin-wall fg dual deploy rocket with a 54mm MMT, so this bird is going to soar. However, I am planning on overbuilding it somewhat, as in my four flights, I have trashed two rockets due to deployment issues. Since I am so new, I figured I would share my plans with all you fine folks in order to get your thoughts and ideas, and to make sure I dont make any huge mistakes (its no fun without little ones though!). In return for your help, Ill give you a build thread! Sound fair? Perfect!
So, on to the plan, from top to bottom:
First, the fin can. This is going to be a doozy! There is only about 1/8in between the outer wall of the MMT and the inner wall of the airframe. I have never really done internal fillets (or external ones, for that matter) before, and this doesnt seem like a good situation to learn in. Therefore, I think it would be better to simply Rocketpoxy the fins to the MMT, foam the admittedly small space between fins, and make good external fillets. In detailed steps, heres what I am going to do.
1. Figure out where the forward CR goes on MMT
2. Sand MMT and CR, then epoxy forward CR in place
3. Sand forward CR and inside of airframe, then epoxy forward CR to airframe. Aft CR will be in place for this step, but with tape tabs for easy removal.
4. Sand and line the bottom of the fin tab with lots of epoxy, the stick into fin slot. Repeat for each fin, then slide fin alignment guide in place
5. Foam the spaces between the fins
6. Sand aft CR and airframe, then epoxy in place
7. Sand end of MMT, and JB Weld motor retainer onto end
However, I do have a few questions here. First, I am using an Aeropack motor retainer, and the outside lines up almost perfectly with the airframe, so I would like there to be as small a gap between the two as possible. Is there a good way to find the right place to place the forward CR so that it lines up with the top of fin slot? Secondly, the fin slots are about 3/8in too long for the fin tab. I am planning on having the fins as far forward as possible, so that any force on them gets translated directly into the airframe, is that a good idea? Thirdly, recovery. The CRs are so thin that I dont really want to sand them down to allow the Kevlar to pass under the forward CR. Therefore, I was planning on looping the Kevlar around the MMT above the upper CR and knotting it, then once again, similar to how you would truss a roast, pulling it tight, then liberally applying epoxy. Thoughts on this method? Fourthly, the two part expanding foam. I did a little test a few days ago, and mixed some. The foam is still fairly compressible and hasnt stiffened up much at all, is this normal? Did I not get a good mixture ratio? How long does it normally take to cure? Fifthly, rail button positioning. I havent used thin-wall fiberglass before, how do I get a good mount of the rail buttons? Lastly for this section, epoxy choice. I currently have Rocketpoxy, JB Weld, and some standard Five Minute. The Aeropack retainer wants JB Weld for its heat resistance, is there anywhere else that needs that kind of heat resistance, or will I be ok using Rocketpoxy for everything else?
Next up, the electronics bay:
The basics here are that I am using and Eggfinder TRS as my main, and a Stratologger CF as my backup I have never used the TRS before, so I am planning on doing a couple low and slow flights to learn the GPS side before I do something crazy. I am comfortable using the Stratologger, so no worries there. Additionally, since I am keeping the TRSs antenna inside the ebay, there wont be any allthread rods running the length of the bay. Instead of the standard setup, I have decided to have a single length of Kevlar running from MMT to nosecone, running through the ebay, with knots on either side to keep it in place. This allows me to build the ebay without worrying much about its strength, as the only part of it that will be structural is the fg coupler portion, which will have shear pins holding either end of the airframe on until deployment.
The ebay itself will also be fairly non-standard. Instead of a single plane, the sled will be shaped like an upside down capital T. All electronics and hardware will be mounted to the vertical board, and the horizontal board acts to shield the electronics from any whipping of the Kevlar. Both boards will be swiss cheesed to ensure the pressure is constant in each section, and to ensure that all four pressure holes are in use.
I dont have a step by step plan for this part, because I dont think the order of steps matters much at all, but essentially it will be assemble the two bulkheads, cut the two boards and epoxy them together, then fit all mounting hardware for electronics, then wire it all up.
I also have a romanticized vision of having a Remove Before Flight tag hanging off the side of the rocket, which gets pulled once the rocket is on the pad to arm the ejection charges. I think this can be done on the Stratologger easily, as described in the Stratologger manual. The TRS manual is less clear on how it would be done, would I have the limit switch short the reset pads? The TRS manual makes it seem like the TRS would have to reconnect to the LCD receiver at that point, but I would like to have had the connection between the two made before I leave my table. Is there a way to achieve this?
Also, batteries. I have never used LiPo batteries before, so guidance there would be appreciated. The TRS manual wants a 2S 7.4V LiPo battery with at least 350 mAH. It also mentions something about a C rating of the battery. What do these all mean? Some suggested batteries would be great also!
Lastly, is there a good place to calculate the size of black powder charges I need, and the number of shear pins? I would do tests, but I am bouncing between my parents house and my dorm room, and neither want me to keep black powder or live motors, and I dont have any casings of my own (I use my clubs casings, or single use motors).
At the top comes the nosecone:
The nosecone is going to be a fairly simple, standard nosecone. Ill have an eyebolt to hold it to the Kevlar, some method of holding the airframe to the nosecone shoulder, and a removable bulkhead in the nosecone shoulder. For holding the bulkhead to the shoulder, I was going to epoxy two nuts to opposite sides of the interior wall, then pass bolts through the bulkhead wall to screw into the nuts. This allows me to add nose weight, or other electronics like a screamer, to the nosecone at a later date. Also, I am cognizant of the fact that epoxying the Kevlar to the MMT means the nose cone end is the only way to get the coupler tube onto or off of the Kevlar, so I want this end to be removable.
What are some good ways to attach the upper airframe tube to the nosecone shoulder so that its removable, should I need to access the nosecone, but solid enough that I dont need to worry about it breaking from the ejection charge? Also, how do I ensure that the bolt holes in the bulkhead line up with the epoxied nuts?
Lastly, recovery:
Not too much going on here, Im having the15in drogue in the aft tube, 36in main in upper tube, nomex for each with quick links and swivels. I think my only question here is that OpenRocket is warning me that with large motors (6GXL, etc), the main chute is deploying at high speed. Is 60-75 fps too fast? Its going to end up weighing 4ish pounds empty. Also, am I crazy for doing the single line of Kevlar thing? Ive never seen it done, on here or irl.
Sorry for the wall of text, there will be pretty pictures to come, I promise!
Thank you all in advance!