LOC Hawk 7.5'' Build Thread

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The sanding device for the tube ends doesn't necessarily need a drill press. Sometimes I have to cut some off an already-built rocket. I run that 10" steel-plate-sanding-disc with an 18v Ryobi drill. It's a handful but it can be done!
 
I'm still sanding the fillets on this rocket. I think I have the tail cone filled and sanded to the point where I want to get a coat of primer on it before I do anymore just to see how it's shaping up. I am planning to sand some more this week and then put a coat of finish epoxy on the fins.
 
I finished applying the color coats (see post #10). I went with a Black / White color scheme - black fins and tailcone, white body. I had some runs in the black that I didn't notice until after pulling off the masking materials. I also reinstalled the 98 mm aeropack retainer in the tailcone. I decided I would fly this beast before I make any further cosmetic changes, though.

My remaining to do list:
- wire up the ebay and nose cone electronics
- drill for shear pins and rivets
- deployment tests
- Figure out how to get the rocket from my garage/hangar bay to the launch site.

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I finally finished the electronics bay (see post #8). I set up the electronics bay so that the bulkheads and the sled (everything but the coupler and switch band) can be used on both rockets, so I cheated and used the same post in this build thread and the LOC VII build thread.

I also took some time to finally fly my Wildman Extreme and get my Level 3 cert.
 
Finally got to launch this rocket at Lucerne today. The rocket weighs in at 36 pounds without the motor, and around 46 pounds with the motor. I launched it on an M1297 (75mm adapted to 98 mm) with the stock 10 foot parachute. More details later, but here are the launch photos (courtesy of Adam Dean):

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I updated the launch report in post #12 with the full launch story. The recovery resulted in significant (but not irreparable) damage to both the booster and the payload bay.
 
Nice flight, Jason. Sorry to have missed it (that 15 traffic was a MESS)!

On the "waggle" issue--aside from the wind, of course--I've found that those back row pads can dance around a lot when launching big rockets. My best guess is that the angled deflector catches the exhaust unevenly, which makes the pad want to twist, leading to wobbly flights and worn rail buttons. (Greg Smith posted a launch video to his website that shows the twist happening.)

I've started taking the deflector off when flying Ls and Ms off those pads; the rocket sits far enough above the ground that the lakebed surface doesn't get scarred from the plume, and my rockets have started flying much straighter ever since.

Lakebed rash sucks, for sure--hopefully after a little fiberglass and paint, you can test the deflector theory on another flight soon :)
 
Nice flight, Jason. Sorry to have missed it (that 15 traffic was a MESS)!

I heard the accident on the 15 was terrible; I managed to avoid it by getting off the 15 at McDonalds and driving through the back way to Lucerne Valley, mostly just luck as I felt like exploring a bit anyway.

On the "waggle" issue--aside from the wind, of course--I've found that those back row pads can dance around a lot when launching big rockets. My best guess is that the angled deflector catches the exhaust unevenly, which makes the pad want to twist, leading to wobbly flights and worn rail buttons. (Greg Smith posted a launch video to his website that shows the twist happening.)

Whoa, I didn't know the pads could twist like that. I certainly wasn't careful about aligning the blast deflector with the nozzle, so that's a distinct possibility. It sounds like the rail button damage could have been caused during launch and not during the sled race the rocket undertook after landing. I'll have to keep an eye out for that in the future.

In hindsight, I should have requested one of the larger tower launchers anyway. I don't really know what the max weight those launch pads can handle, but with the large fin area and the high cross winds during launch, I'm curious just how much risk I took with that launch. Do you know what the maximum weight/height rocket the large rail pads in the back should take?

Lakebed rash sucks, for sure--hopefully after a little fiberglass and paint, you can test the deflector theory on another flight soon :)

Yeah, I'm certain I can repair it, just not certain I can repair it to the same length as the original unless I "move" some of the length from the payload section to the booster section. I'm still planning my repair strategy...
 
WOW... That is some serious lakebed rash... How many miles did it take to do that??? :eek:

Best guess was about a mile or so, but it wasn't just the distance - it was the velocity followed by the sudden change in velocity at the end of the run. The wind velocity was right around 20 mph, and the rocket fins acted as sled rails for the 10 foot parachute, so I imagine the rocket was moving pretty fast when it hit the gully. We followed the two parallel lines (looked almost like railroad tracks) back for at least a mile when we finally caught the rocket. The only reason we were able to catch the rocket was because the forward end of the booster embedded itself in the side wall of a gully. The rocket was full of lakebed when I finally brought the parachute down.
 
I don't really know what the max weight those launch pads can handle, but with the large fin area and the high cross winds during launch, I'm curious just how much risk I took with that launch. Do you know what the maximum weight/height rocket the large rail pads in the back should take?
Since I started taking the deflector off, I've flown lots of Ms in 40-60 lb 5"-6" x 10-12 ft rockets off those pads with no issue. They're heavy and have a nice, stable, wide footprint. The big fins on the Hawk may have been a challenge in the breeze--I bet the pad scooched around a little as it left the rail--maybe keep a set of stakes with the rocket, staking down the pad is less work than setting up one of the uberpads ;)

That being said, back in 2013 or so, cvanc did manage to bend the Unistrut leg of one with an N10,000, so I think the upper limit is somewhere around there! (To the pad's credit, his rocket suffered from bad rail button placement that caused severe rail whip, and the leg got stuck in the mud as the rocket turned.)
 
Since I started taking the deflector off, I've flown lots of Ms in 40-60 lb 5"-6" x 10-12 ft rockets off those pads with no issue. They're heavy and have a nice, stable, wide footprint. The big fins on the Hawk may have been a challenge in the breeze--I bet the pad scooched around a little as it left the rail--maybe keep a set of stakes with the rocket, staking down the pad is less work than setting up one of the uberpads ;)

How do you remove the deflector? Does it just slip out, or do you need to unbolt something? Maybe I can pick your brain a bit at the next ROC launch, assuming the 15 stays open and the rains cooperate...


That being said, back in 2013 or so, cvanc did manage to bend the Unistrut leg of one with an N10,000, so I think the upper limit is somewhere around there! (To the pad's credit, his rocket suffered from bad rail button placement that caused severe rail whip, and the leg got stuck in the mud as the rocket turned.)

What was the "bad rail button placement" - it was hard to tell the placement from the picture, only the obvious effect.

Thanks, David!
 
Jason,

Re: deflating your 'chute, I saw someone have to deal with this, and what they did was ingenious: grab the 'chute by the edge (or one of the shroud lines near the edge) and then walk into the "W". Took the "W" right out of the sail!

Mike
 
Ayii, logging in for the first time in a month--sorry for not getting back to you before the last launch!
How do you remove the deflector? Does it just slip out, or do you need to unbolt something? Maybe I can pick your brain a bit at the next ROC launch, assuming the 15 stays open and the rains cooperate...
Yes, the deflector slips out, you just pull straight up--there's a pin on the back that slips into a receiver on the pad. Drop it on the lakebed right under the pad so you still meet the safety code requirement :)
What was the "bad rail button placement" - it was hard to tell the placement from the picture, only the obvious effect.
The upper button was too low on the rocket--way aft of the CG. The rocket pivots around the CG, so any movement as it clears the rail is around that point. The thrust vector also goes through the CG--not through the rail. So, if the forward button is aft of the CG, the rocket pivots into/away from the rail, leading to bad whip.

Sorry we didn't cross paths at last month's launch. Sad it got windy :( but I still flew one back row rocket. Deflector off, of course! :)
 
Ayii, logging in for the first time in a month--sorry for not getting back to you before the last launch!

Yes, the deflector slips out, you just pull straight up--there's a pin on the back that slips into a receiver on the pad. Drop it on the lakebed right under the pad so you still meet the safety code requirement :)

The upper button was too low on the rocket--way aft of the CG. The rocket pivots around the CG, so any movement as it clears the rail is around that point. The thrust vector also goes through the CG--not through the rail. So, if the forward button is aft of the CG, the rocket pivots into/away from the rail, leading to bad whip.

Sorry we didn't cross paths at last month's launch. Sad it got windy :( but I still flew one back row rocket. Deflector off, of course! :)

thanks, David! I wasn’t able to attend the last launch, so it would have been really amazing if we did cross paths! I will look at the placement of my rail buttons relative to the final CG location, i don’t think i did that before placing the rail buttons, or if i did, the button was placed based on a very early estimate of the CG location.
 
Fantastic work! Only sorry I missed your flight. An inspiration!
I love the fin whistle after burnout... though maybe yours was already too high to hear. (Couldn't catch it in videos).
 
Fin Installation

Once the glass was cured on the booster section, I was able to instal the first fin, which was a little more challenging than I was expecting just due to the size and flexibility of the fins, and the challenge in trying to clamp the large pieces together.

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Adding the fin fillets with that excess sock in the way is going to be frustrating, so I may trim it off and just glass the tail cone separately once its installed [Update] I did remove the excess sock at the aft end. It really was in the way with the internal fillets, which were complicated enough as is.

I let that first fin cure overnight, and installed the remaining fins today. After installing the remaining fins, I noticed that the first fin is not aligned correctly. I tried to pop it off to realign it, but the epoxy had cured and I feared I might permanently damage the motor mount if I forced it, so I'll have to live with the misalignment.

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Once the initial fin attachments were cured, I started doing the fillets. There are 2 external and 4 internal for each fin times 4 fins means 24 fillets. While the rocket is fixed in one horizontal position, I will do 2 external fillets, two internal fillets to the motor, and two internal fillets to the airframe all at the same time, then rotate the rocket 180 degrees and repeat. This way I can do the six fillets that have gravity in the right direction and then rotate the rocket. Even with the fin roots tacked to the motor mount tube, these fins are still loose at the forward end and will be loose until the external fillets are completed.

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Here's the initial round of fillets using an incredible amount of Rocket Poxy (I used something like 350 grams of epoxy just for these first 6 fillets).


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Also, I have drilled the holes for the rail buttons but will wait to install them until I complete all of the fin fillets and do some sanding.

Update 1/15/19: I have completed all of the internal and external fin fillets and have installed the rail buttons. I also installed the aft centering ring with the loc-n-fin notches that mate to the tabs on the aft side of the fins. Once that centering ring (CR3) was installed, I was able to install the tail cone subassembly (see post #5 above) and epoxy it in place at the motor tube and aft end of the airframe. I have left the final centering ring off and have yet to seal up the tail cone.

View attachment 371676
I followed much the same fillet approach on my L2 MegaMagg (inspiration from J.Coker)...also seemed like going thru a lot of epoxy.
To you: fantastic build, an inspiration. Hawk is my favorite rocket.
 
Did you ever build/fly an Eggfinder in the Hawk?

I build a simple skid to slide into the RNWS of my stretched MegaMagg (w a lanyard to extract it).
The skid can be placed:
(a) aft of the weight cartridge, with the NC eyebolt fit to the RNWS hatch (a washer stack centers the bolt and fender washers spread the load)
or
(b) forward of the weight cartridge (if that still works for CG) allowing "normal" eyebolt connection.


IMG_4475.jpg
 
Did you ever build/fly an Eggfinder in the Hawk?

I build a simple skid to slide into the RNWS of my stretched MegaMagg (w a lanyard to extract it).
The skid can be placed:
(a) aft of the weight cartridge, with the NC eyebolt fit to the RNWS hatch (a washer stack centers the bolt and fender washers spread the load)
or
(b) forward of the weight cartridge (if that still works for CG) allowing "normal" eyebolt connection.


View attachment 543292

I have the bay in the nose for the eggfinder, but the one time I flew the rocket I failed to turn it on. So, the answer to your question is both yes and no.
 
Thank you all who posted builds of the 7.5 Hawk. I have been planning mine for a while and got around to tackling the Boat Tail. I think I got a later version, as the fins have slots like the Laser series, and the boat tail bulkhead does not go inside the coupler; rather, it is a flush fit. It will install back to back with the lower slotted Centering ring, so it's doubled up there. Swapped out the forward short tube for a longer one so it looks more proportional; wish me luck as I prepare to glass my tubes today. And no, the engine tube is not epoxyed in place. It's in there to get the alignment correct; as I have found out in the three boattails I have worked with, they are a bugger to keep everything aligned and the distance correct so all of the centering rings are in the correct spot, so the tail is not hanging out too far or in to deep.
 

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More progress today. Switch band, Upper tube completed and a side shot of the assembled boat tail. Two more body tubes to go, then onto fiberglassing the fins and working on getting the motor mount figured out. The fins are slotted so everything has to line up right the 1st time.
 

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More updates from the long weekend, eBay is coming together, I reinforced the boat tail which was described in the thread. If someone could check how much weight you put in the nose I could use that as a starting point. 🙏
 

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