This evening I pulled the last external fillets, and finished the CA/filling of the pullaway plugs.
I'm going to really have to shelve this one now...Airfest is almost here.
I'm going to really have to shelve this one now...Airfest is almost here.
V2 for my L3
- Thread starter Cl(VII)
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Mein Fuhrer...I can build!
After a Post Airfest slump I am back at it. Actually, I have been doing some work on and off, but I'll try to catch the thread up now.
Aft Fillets: The fins wrap around the aft end, and as such need fillets there too. This was easy, but required a lot of tape, and some milled fiberglass thickened Aeropoxy.
dixontj93060
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3 mos. hiatus--not too bad. Glad you are back at it!
This thing needs lots of holes drilled:
- 4 altimeter vent ports/altimeter power switch access (13/64"...lots of math, but not too hard. I followed the RRC3 instructions for port sizing and got 0.161", then sized up a touch to 0.203")
- 2 vent holes (1 in each parachute bay)
- 4 aft shear pin holes (2-56, drogue bay)
- 4 fore shearpin holes (4-40, main bay)
- 2 rail button holes (accepting 10-24 threaded inserts)
- 4 camera shroud mounting holes (accepting 6-32 threaded inserts)
Started off by drawing index lines the length of the rocket every 45 degrees. Then drilled the 4 altimeter vent holes making sure that they were low enough too align with the switch position of the 3D printed altimeter sleds. othing fancy, just drill and sand.
Drilled the 4 fore shear pin holes through the NC and bt one at a time, and the bt hole was tapped 4-40. Before each successive hole was drilled a 4-40 screw was placed in the preceding hole(s) to ensure alignment when all are drilled. Once all four were drilled the holes in the NC were enlarged slightly to facilitate sheared pin removal later. The aft shear pin holes were then drilled in the same manner, but lacking a 2-56 tap I used a 2-56 screw to create threading...not as smooth but it works. The boat tail shear pin holes were also enlared to maake removing shared pins easier.
For the 1515 Rail buttons I want them spaced as far as is practical. I modified a Doghouse Rocketry standoff to allow for placement of the aft RB into the CR topping the fin tabs in the boat tail. Unfortunately I didn't mark this spot when putting in the rings, and they are now inaccessible for measurement, so a bt of prospecting got me the correct spot, but also a small hole to fill. Since the 1515 buttons use 10-24 screws It needs a big threaded insert...the CR isn't really thick enough to rely on only (the hole tore through the bottom side ~270 deg of hole in CR), so the insert was covered on one end with tape and screwed into the CR along with a generous glob of 5 min epoxy.
The Fore rail button needed a backing block for the RB threaded insert, so one was shaped free hand on the belt sander from a stack of scrap plywood, and epoxied into place. This was drilled out and the insert put in.
A nice wide stance for the RBs should minimize the torque and any potential binding.
- 4 altimeter vent ports/altimeter power switch access (13/64"...lots of math, but not too hard. I followed the RRC3 instructions for port sizing and got 0.161", then sized up a touch to 0.203")
- 2 vent holes (1 in each parachute bay)
- 4 aft shear pin holes (2-56, drogue bay)
- 4 fore shearpin holes (4-40, main bay)
- 2 rail button holes (accepting 10-24 threaded inserts)
- 4 camera shroud mounting holes (accepting 6-32 threaded inserts)
Started off by drawing index lines the length of the rocket every 45 degrees. Then drilled the 4 altimeter vent holes making sure that they were low enough too align with the switch position of the 3D printed altimeter sleds. othing fancy, just drill and sand.
Drilled the 4 fore shear pin holes through the NC and bt one at a time, and the bt hole was tapped 4-40. Before each successive hole was drilled a 4-40 screw was placed in the preceding hole(s) to ensure alignment when all are drilled. Once all four were drilled the holes in the NC were enlarged slightly to facilitate sheared pin removal later. The aft shear pin holes were then drilled in the same manner, but lacking a 2-56 tap I used a 2-56 screw to create threading...not as smooth but it works. The boat tail shear pin holes were also enlared to maake removing shared pins easier.
For the 1515 Rail buttons I want them spaced as far as is practical. I modified a Doghouse Rocketry standoff to allow for placement of the aft RB into the CR topping the fin tabs in the boat tail. Unfortunately I didn't mark this spot when putting in the rings, and they are now inaccessible for measurement, so a bt of prospecting got me the correct spot, but also a small hole to fill. Since the 1515 buttons use 10-24 screws It needs a big threaded insert...the CR isn't really thick enough to rely on only (the hole tore through the bottom side ~270 deg of hole in CR), so the insert was covered on one end with tape and screwed into the CR along with a generous glob of 5 min epoxy.
The Fore rail button needed a backing block for the RB threaded insert, so one was shaped free hand on the belt sander from a stack of scrap plywood, and epoxied into place. This was drilled out and the insert put in.
A nice wide stance for the RBs should minimize the torque and any potential binding.
Got me one of those sweet Landru 3D printed Mobius Camera Shrouds, but I want it to be removable (for a reason I have yet to determine). The shroud is made to be fitted to a 7.5" bt, but I plan to use it on the boat tail...I just don't want anything pulling the CP forward that doesn't have to. I am mindful though that I can't get too close to the business end as an "M" will put out a lot of fire (which is sweet), but could white out the camera (which would be decidedly not sweet), so I settled on top of the boat tail, and on the opposite side from the RBs...try to balance the draggy bits.
On the draggy bits note, I've decided not to use the do-dads I made for the scale-ish bits, basically progress won out of detail...sometimes you just need a project done, and I'm getting close.
'Anyhow, the camera had to be profiled t the boat tail, so nothing fancy, just taped on some sandpaper and went to work. Not an exact fit, but I didn't want to thin the top of the shroud anymore, so the gap at the bottom is minimal. Definitely a better fit than stock would have been. The holes were then marked off, drilled, and threaded insert were put with a little 5 min epoxy to ensure they set well...they did. Fits nice I think.
On the draggy bits note, I've decided not to use the do-dads I made for the scale-ish bits, basically progress won out of detail...sometimes you just need a project done, and I'm getting close.
'Anyhow, the camera had to be profiled t the boat tail, so nothing fancy, just taped on some sandpaper and went to work. Not an exact fit, but I didn't want to thin the top of the shroud anymore, so the gap at the bottom is minimal. Definitely a better fit than stock would have been. The holes were then marked off, drilled, and threaded insert were put with a little 5 min epoxy to ensure they set well...they did. Fits nice I think.
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Big moment in the build on Saturday, and then this evening. The first layer of filler primer is on. On Saturday I did the NC and boat tail by roughing up with 80 grit, wiping down with ethanol, taping off (and blocking holes with screws) and putting on a healthy coat of Rusto Filler Primer. Tonight I did the same to the bt, sans the rough up.
They look way better in the pic than in person, gonna need a lot of bondo, but on the way.
That brings me up to date.
With the loss of the HOTROCs Asa field, I am targeting Airfest next year for the flight assuming my L3CC member is attending. Based on the rate I finish rockets, I may have enough time to get this thing done, but no guarantees.
They look way better in the pic than in person, gonna need a lot of bondo, but on the way.
That brings me up to date.
With the loss of the HOTROCs Asa field, I am targeting Airfest next year for the flight assuming my L3CC member is attending. Based on the rate I finish rockets, I may have enough time to get this thing done, but no guarantees.
rharshberger
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Its coming along very nicely, keep up the good work.
dixontj93060
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With the front rail button that far forward aren't you worried that it will come off the rail before the rocket hits a reasonable launch velocity?
Maybe, but it will definitely be taken into account on the sim before flight (I'll edit down the rail length, and look at the stability margin at rail clearance). The most I could have drawn it aft was about 7" (that would have put it in the aft donut bay CR), however, I didn't want to get that much weight in front of the forward button with such a short span between...that is my thinking anyway. The picture also distorts things a bit; I believe those buttons are about 18-20" apart (don't remember exactly), so not the great distance they may appear.
In the end, if I have doubt, I'll get an M1315W reload for the same case, and fly with that first. I'll then have the M650 for a later V2 flight, or a 75 MD project down the road. The M650 is 1475 N on startup, and the M1315 is 2362 N. So I'm sure I'll have an option for even short-ish rails.
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Just curious, will it need nose weight or are the forward tubes and nosecone heavy enough to ensure stability? Weight can be ones friend especially if trying to stay within a waiver and is needed for balance purposes.
Very nice looking. Kurt
Very nice looking. Kurt
It will definitely need nose weight...multiple pounds depending on motor. There is a removable bulkhead that will allow for adjustable nose weight in the NC. Some weight will probably be permanently cast into place also.
James Duffy
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What sort of finishing scheme do you have planned for this beastie?
James
James
The black and white roll pattern from the first successful flight. Check out post 93 for a bit of discussion and link to a thread with quite a few paint schemes in it.
It would be a great place to put that mega QCC Explorer of your's in the air too.
James Duffy
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blackstool102
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Anybody have any info on the polecat 7.5 V-2?? I'm planing my level 2, I am a little confused on reinforcing the fins with carbon fiber. I am told to layup fiberglass over the carbon. because carbon fiber has no give. .. I am an a&p mechanic, who works composites so i have a good background /working knowledge. would love to alos do duel deployment. tanks craig
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I believe Polecat thinks no reinforcement is needed, although it isn't a bad idea. For sport flying, sub-Mach, birch plywood is fine, but reinforcement will increase durability a lot. Carbon is extremely stiff and strong. The fiberglass on top is usually to give you something to sand that is cheap and not important for strength. The fiberglass won't take much of the stress because the carbon is so stiff. Remember though, that especially on something like a V2, stability becomes an issue, and the extra weight of composite reinforcement aft becomes problematic fast.
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Some people will cut out holes in the fins, fill them with foam and carbon fiber over the top as a weight reduction technique. This probably won't net too much unless you are vacuum bagging.
rharshberger
Well-Known Member
Exactly, the weight savings was minimal when I did it on my Cherokee D upscale L3 project, however the fins were MUCH stiffer, the cores were endgrain balsa and the ply was 1/4" Baltic birch with two layers of 5.6oz CF twill each side, and vacuum bagged. The weight savings was about 10% iirc, foam might have saved another 5%.
Post 80 of this thread has my composite fin process with before and after masses. Saved about 0.7 lb across the set versus bare ply, or about 1.7 lb versus laminated ply.
rharshberger
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You saved considerably more weight because of the higher percentage of ply removed, very nice work. I have been following this thread since day one.
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15% less tailweight is some combination of less noseweight and/or less fin area. Still love that build
I ran mine as close to the edge as I dared, and wouldn't have gotten this aggressive without the full test fin. It was a lot of work for that weight savings.
blackstool102
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thanks
After getting my bench back from Christmas wrapping central (now only sharing with Lego kits and the boys' RC cars) the finishing continues. i.e. bondo, sand, primer, bondo...
Rd 1 is complete, and Rd 2 has begun. Rd 1 made a lot of progress, but I scratched up the NC and boat tail too much before primer. While I certainly gained the tooth I was looking for, I'm going to need more cycles to clean it up than I had wished...oh well. I let primer cure for at least a week before sanding because it doesn't clog sand paper at that point which makes the process way easier.
Rd1 Post Bondo:
Rd1 Post sanding:
Rd2 Post primer and Bondo:
Rd 1 is complete, and Rd 2 has begun. Rd 1 made a lot of progress, but I scratched up the NC and boat tail too much before primer. While I certainly gained the tooth I was looking for, I'm going to need more cycles to clean it up than I had wished...oh well. I let primer cure for at least a week before sanding because it doesn't clog sand paper at that point which makes the process way easier.
Rd1 Post Bondo:
Rd1 Post sanding:
Rd2 Post primer and Bondo:
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Nytrunner
Pop lugs, not drugs
Which Bondo Spot and Glazing putty do you use?
I picked up a tube and used it on my recent leviathan build, but its white (unlike the red color I usually see in people's photos).
I picked up a tube and used it on my recent leviathan build, but its white (unlike the red color I usually see in people's photos).
A visually unexciting progress report (at the pool and left the camera at home). There has been much key progress, but most of it will sound mundane.
Aesthetically:
The finishing cycles continue, but I'm one more bondo/prime/sand cycle from declaring done regardless of remaining imperfections. The paint scheme plan has been changed. I'm doing the field deployed ragged camo (several cycles of paint testing went into nailing down the cans of choice). This change will help obscure surface imperfections and body diameter discrepancies better than the roll pattern, that's the thinking anyway. I will post the arrived at products and a pic of the test piece soon. I'll probably top that off with some Stickershock accents also.
Weight:
I had to figure out the final weight, at least to within about 10% so I could finalize the recovery elements and get those ordered. The first step was getting good weights and CGs for the individual segments with all of their non-recovery components, these appear below.
Nose: 49.5 oz, CG 15.5"
Body: 66.5 oz, CG 7.25"
Fin can/Boat tail: 139.0 oz, CG 12"
I pegged everything together, and got a CG of 39.5" for the rocket sans recovery and motor. The CG needs to be 35.4" to have 1 cal stability according to Rocsim, which agreed nicely with the OR file with the three major component masses and CGs over ridden. I feel like all the effort to save weight on the fins was well worth it now. There will probably be two kinds of nose weight; permanent and adjustable. I used the sim to figure out the motors that this rocket could reasonably fly on to determine the best case contribution to stability motor and the worse case motor based on their weight balance. These along with the projected recovery component weights (more on this in a minute) give me a clear best motor, the AT K1103X which would require 3 lbs of nose weight to achieve 1.0 cal stability (this will be the fixed weight amount). There are many candidates for the worse case motor across multiple cases, but the moral is that many motors (including the M650) will require about 6 lbs of nose weight for stable flight. Therefore, at least three pounds of nose weight needs to be adjustable in increments of about 1 lb ideally. To allow for additional weight should everything not balance out correctly I will cast as many weights as I have room for. Back of the envelope space calculation says about 5-6 lbs are likely doable. More on making these weights soon...I've experimented with steel shot and have a good method, but my 25 lb sack of #9 lead shot doesn't arrive until tomorrow. The good news is that this brings liftoff weight with the M650 in at between 30-33 lbs conservatively. With the initial thrust of the M650 being about 1250 N that gives me about a 10:1 thrust to weight ratio on liftoff...safe, but not too fast...I think this plan may work.
Recovery:
The other reason for the more detailed weight evaluation is to size the recovery components. I don't have anything nearly this big. My heaviest rocket is about 12 lbs pad weight with a K in it, so the main definitely has to be new. I have some constraints also, the main one being the limited space to put the main. It has to fit in a 3.9" ID tube that is 15" long...that's it for a chute to lower a 30 lb rocket, i.e. packing size will be the primary consideration. I put out a call for advice to a friend who flies BIG rockets, but in an act of stupidity I sent the email to the entire HOTROC yahoo group...this turned out good as my buddy has dropped of the map (anyone seen Robert Vanover recently?), but several of the Tripoli Houston folks responded with advice, which included an offer to test fit exactly the equipment I was thinking about into my V2. So, I made the 2.5 hr trip south to the Tripoli Houston monthly launch and got some help for TRF's own "Wizard" (thanks again David)...also flew a couple rockets, so productive and fun.
All that to tell you that the chutes will all be coming from Fruity Chutes. The main will be a 96" Fruity Chutes Iris Compact, in a 4" x 12" deployment bag, with a 24" compact elliptical as pilot. The drogue will be a 36" compact elliptical. This setup should give me right at 50 ft/sec under drogue, and 15 ft/sec under main...I want to land this thing with all the force of a butterfly given those fins. This will all fit with some space to spare, and I've chosen to spring for the compact variants as I see these filling niches that I currently struggle to fit my existing chutes in...all should ultimately be double-duty.
I was really going to try to get by with cheaper chutes, but given the space requirements and how much money and WORK I have in this project I've decided to go with the absolute best option I can come up with...even if that is $600 in recovery gear. I know there is as much personal preference (and contention) around parachutes as their is epoxies, so many of you will think I'm nuts, and you're probably right.
Aesthetically:
The finishing cycles continue, but I'm one more bondo/prime/sand cycle from declaring done regardless of remaining imperfections. The paint scheme plan has been changed. I'm doing the field deployed ragged camo (several cycles of paint testing went into nailing down the cans of choice). This change will help obscure surface imperfections and body diameter discrepancies better than the roll pattern, that's the thinking anyway. I will post the arrived at products and a pic of the test piece soon. I'll probably top that off with some Stickershock accents also.
Weight:
I had to figure out the final weight, at least to within about 10% so I could finalize the recovery elements and get those ordered. The first step was getting good weights and CGs for the individual segments with all of their non-recovery components, these appear below.
Nose: 49.5 oz, CG 15.5"
Body: 66.5 oz, CG 7.25"
Fin can/Boat tail: 139.0 oz, CG 12"
I pegged everything together, and got a CG of 39.5" for the rocket sans recovery and motor. The CG needs to be 35.4" to have 1 cal stability according to Rocsim, which agreed nicely with the OR file with the three major component masses and CGs over ridden. I feel like all the effort to save weight on the fins was well worth it now. There will probably be two kinds of nose weight; permanent and adjustable. I used the sim to figure out the motors that this rocket could reasonably fly on to determine the best case contribution to stability motor and the worse case motor based on their weight balance. These along with the projected recovery component weights (more on this in a minute) give me a clear best motor, the AT K1103X which would require 3 lbs of nose weight to achieve 1.0 cal stability (this will be the fixed weight amount). There are many candidates for the worse case motor across multiple cases, but the moral is that many motors (including the M650) will require about 6 lbs of nose weight for stable flight. Therefore, at least three pounds of nose weight needs to be adjustable in increments of about 1 lb ideally. To allow for additional weight should everything not balance out correctly I will cast as many weights as I have room for. Back of the envelope space calculation says about 5-6 lbs are likely doable. More on making these weights soon...I've experimented with steel shot and have a good method, but my 25 lb sack of #9 lead shot doesn't arrive until tomorrow. The good news is that this brings liftoff weight with the M650 in at between 30-33 lbs conservatively. With the initial thrust of the M650 being about 1250 N that gives me about a 10:1 thrust to weight ratio on liftoff...safe, but not too fast...I think this plan may work.
Recovery:
The other reason for the more detailed weight evaluation is to size the recovery components. I don't have anything nearly this big. My heaviest rocket is about 12 lbs pad weight with a K in it, so the main definitely has to be new. I have some constraints also, the main one being the limited space to put the main. It has to fit in a 3.9" ID tube that is 15" long...that's it for a chute to lower a 30 lb rocket, i.e. packing size will be the primary consideration. I put out a call for advice to a friend who flies BIG rockets, but in an act of stupidity I sent the email to the entire HOTROC yahoo group...this turned out good as my buddy has dropped of the map (anyone seen Robert Vanover recently?), but several of the Tripoli Houston folks responded with advice, which included an offer to test fit exactly the equipment I was thinking about into my V2. So, I made the 2.5 hr trip south to the Tripoli Houston monthly launch and got some help for TRF's own "Wizard" (thanks again David)...also flew a couple rockets, so productive and fun.
All that to tell you that the chutes will all be coming from Fruity Chutes. The main will be a 96" Fruity Chutes Iris Compact, in a 4" x 12" deployment bag, with a 24" compact elliptical as pilot. The drogue will be a 36" compact elliptical. This setup should give me right at 50 ft/sec under drogue, and 15 ft/sec under main...I want to land this thing with all the force of a butterfly given those fins. This will all fit with some space to spare, and I've chosen to spring for the compact variants as I see these filling niches that I currently struggle to fit my existing chutes in...all should ultimately be double-duty.
I was really going to try to get by with cheaper chutes, but given the space requirements and how much money and WORK I have in this project I've decided to go with the absolute best option I can come up with...even if that is $600 in recovery gear. I know there is as much personal preference (and contention) around parachutes as their is epoxies, so many of you will think I'm nuts, and you're probably right.
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