Very interested to see how the paint holds up!
Making plans for StratoSpear again
- Thread starter Adrian A
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Me too!
I'll use this space for some notes on the post-curing process, which I'm going to complete before painting the nosecone and then post-curing it. In the kitchen oven I have the sustainer body and the nosecone, each with a motor case in place to hold the shape if they get too soft. Both are sanded to 320 grit. The sustainer body is fully encapsulated in a thin layer of resin, and the nosecone is mostly encapsulated but has some bare-carbon spots. The nosecone will get paint, so I'm not going to add another thin epoxy layer for it. The nosecone has has only a room temperature cure for about 14 hours on its final epoxy coat, but the sustainer was cured at 170F.
I started the post-cure process with 30 minutes at 170F to ensure the nosecone epoxy is fully cured before going higher. Then 30 minutes at 200F. I inspected the parts after each step, and they came out still hard and smooth at this point. Now they are post-curing for 1 hour at 250F.
I checked on it after it was at 250F for 15 minutes, and when the parts are set on the counter, they still ring a little, but the ring is much deader than when they are cold.
Now they have been at 250F for over an hour and they are fine.
After a bad experience with this last year,
I’m starting with 300F for the next phase and crossing my fingers.
Last year’s nosecone had a lot more cast tungsten-epoxy volume, causing the high temperature expansion problem. This time I have my harness attachment bolt that goes almost to the tip, and just a little of the tungsten-epoxy mixture because this time the sustainer gets its stability with larger fins rather than nose weight.
Now they have been at 250F for over an hour and they are fine.
After a bad experience with this last year,
I’m starting with 300F for the next phase and crossing my fingers.
Last year’s nosecone had a lot more cast tungsten-epoxy volume, causing the high temperature expansion problem. This time I have my harness attachment bolt that goes almost to the tip, and just a little of the tungsten-epoxy mixture because this time the sustainer gets its stability with larger fins rather than nose weight.
No visible deformation at 300F, so going up to 350F now and starting the 1 hour clock.
After an hour+, the only damage was some yellowing of the epoxy that's noticeable on the FG section of the nosecone. There are a few tiny pinpoint spots on the sustainer where the resin sort of popped out. The nosecone had a very slight change in surface shape near the potted part, only noticeable when I dry-sanded the nosecone again in preparation for its paint.
I painted the nosecone, and it's super rough in places. I may try sanding it down a bit and maybe add another coat. The previous Cotronics stainless spraypaint product went on easier than any other spraypaint I have used. This stuff, not so much.
After an hour+, the only damage was some yellowing of the epoxy that's noticeable on the FG section of the nosecone. There are a few tiny pinpoint spots on the sustainer where the resin sort of popped out. The nosecone had a very slight change in surface shape near the potted part, only noticeable when I dry-sanded the nosecone again in preparation for its paint.
I painted the nosecone, and it's super rough in places. I may try sanding it down a bit and maybe add another coat. The previous Cotronics stainless spraypaint product went on easier than any other spraypaint I have used. This stuff, not so much.
At least the paint dries really fast. I wet-sanded the cone, and then put another coat on. It's drying now. I think I'll sand it again before starting the post-cure so that in case I sand too far I can put another coat on before I spend all that time.
Ok, sanding done and the cone weighs 5.0 grams more than before paint. It’s in the oven now, starting a slow ramp to 450F. I’ll let it sit at 180 for a while to make sure it’s really dry.
Ok, sanding done and the cone weighs 5.0 grams more than before paint. It’s in the oven now, starting a slow ramp to 450F. I’ll let it sit at 180 for a while to make sure it’s really dry.
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I hope your new wife doesn't mind using the kitchen appliances to thermally cure epoxy 
We each have our own houses for the time being. 
But I do need to get the house de-stinked before dinner (takeout). I’ll do an oven cleaning cycle before we use it again for food.
But I do need to get the house de-stinked before dinner (takeout). I’ll do an oven cleaning cycle before we use it again for food.My 'not so new' wife does mind the aromaI hope your new wife doesn't mind using the kitchen appliances to thermally cure epoxy
I got some pebbling of the surface finish at 210F, which I have sanded off again. There are some pinholes in the paint in its place. After a couple of steps I’m up to 320 now.
We each have our own houses for the time being.
Ahh, I normally thermally cure my epoxy in the back of my hatchback in the Tucson summer. Good enough for Aeropoxy, not good enough for Cotronics it seems. I haven't measured the temp inside my car, but I keep a jar of 'Cerrolow 117' in a jar in my car, which is a metal alloy that melts at 117F, and it's always very fluid in the summer afternoons.
After I ramped up to 350F and held it there for a while, I took it out and pondered if I really want to keep going to 450 to fully cure the paint, or maybe I should just sand the paint off. I'm not sure how much the paint could really protect the epoxy underneath. There is a big advantage to both drag and aeroheating to keep the boundary layer laminar as long as possible. I have been intentionally avoiding an aluminum tip because I have seen the discontinuity at the rear edge of the trip the boundary layer turbulent, based on extra aerodynamic damage there. If the paint starts to scrub off at the tip and causes extra roughness, it could do more harm than good. I'm also worried about going to 450F to cure the paint when the epoxy rated temperature is 500F and I saw some yellowing after the cure at 350F. But if the paint can delay or reduce aeroheating damage of the underlying material, then it would be good to keep it.
The paint is now hard, smooth, and has little/no odor. Earlier I took off the blue tape from the ends of the shock cord, since that was getting stinky during the 350F epoxy cure, and that helped. It seems to have handled 350F well. I'm going to go for the 450F cure.
The paint is now hard, smooth, and has little/no odor. Earlier I took off the blue tape from the ends of the shock cord, since that was getting stinky during the 350F epoxy cure, and that helped. It seems to have handled 350F well. I'm going to go for the 450F cure.
Well, the nosecone seemed to survive 450F for the 70 minutes I had it in the oven. There are a couple of pinprick resin eruptions like there were on the sustainer fin can, but otherwise it came out great. I’m relieved to have this part done. I might replace the Kevlar nosecone harness, but in theory these temperatures should not have bothered it.
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I'm glad it survived! being this close to the planned launch, that would have been really bad if it failed.
Neutronium95
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Have you looked into ceramic coatings? I'm considering using Cerakote C-7600 on an upcoming build. It's super temperature resistant, and doesn't need elevated temperatures to cure.
Good luck with the launch and the record.
Yes, if I hadn’t tested the same materials at the same temperatures yesterday I wouldn’t have risked it.
No, but I was just wondering about that today. Thanks for the link. The Cotronics ones need an elevated cure but I forget how high.
How's your RF strength through the Stainless Paint? Any attenuation?
I did a test with the new aluminum paint last week that showed very slight, if any, attenuation. I used a fiberglass tube that I painted, and I put a Featherweight GPS tracker inside with a motor case in each end. I compared the GPS satellite signal strength and the LoRa signal strength with the tracker in and out of the tube. But I should re- test now with my real nosecone and chute cannon in case that configuration or the post-curing has changed that.
Adrian --
I don't know how relevant this is after 25 years, but I bought all the materials for my 4-inch min diameter level 3 rocket in 1998.
I worked with Elanor and an engineer at Cotronics about what I was trying to accomplish and she and the engineer I were very interested in my level 3 project.
She faxed the marketing sheets attached below ( .pdf format, opens in a separate window ).
EDIT: The .pdf does not open here in TRF. I'll work on a clean FAX-to-PDF conversion.
I ended up ordering the products below.
If I remember correctly, the Cotronics Duralco 4461 and the Cotronics 4525N cure at room temperature but are rated for 500F.
And referring to my old notes, after speaking to the engineer, I built a 250F hot box for a 2-hour post cure at 250F .
My goo's are still in the original shipping containers but after 25 years, I am afraid to use them any more.
And I don't know how relevant these materials are any more ... a lot has changed in 25 years !
HTH
-- kjh
I don't know how relevant this is after 25 years, but I bought all the materials for my 4-inch min diameter level 3 rocket in 1998.
I worked with Elanor and an engineer at Cotronics about what I was trying to accomplish and she and the engineer I were very interested in my level 3 project.
She faxed the marketing sheets attached below ( .pdf format, opens in a separate window ).
EDIT: The .pdf does not open here in TRF. I'll work on a clean FAX-to-PDF conversion.
I ended up ordering the products below.
If I remember correctly, the Cotronics Duralco 4461 and the Cotronics 4525N cure at room temperature but are rated for 500F.
And referring to my old notes, after speaking to the engineer, I built a 250F hot box for a 2-hour post cure at 250F .
My goo's are still in the original shipping containers but after 25 years, I am afraid to use them any more.
And I don't know how relevant these materials are any more ... a lot has changed in 25 years !
HTH
-- kjh
Code:
September 23, 1998
Elanor --
Please find enclosed a Money Order for $293.70 to cover the following
order and shipping.
Thank you for your assistance.
+------+------+----------------------------------------+-------+--------+
| Qty | Unit | Description | Price | Amount |
+------+------+----------------------------------------+-------+--------+
| 2 | pint | Duralco 4461-1 500 F Pint Trial Kit | 49.95 | 99.90 |
| 2 | box | EE 4525N -- 50 Gram Epox-Eez Kit | 69.95 | 139.90 |
| 2 | kits | Epox-Eez 454 454B-1 Applicator Kits | 21.95 | 43.90 |
| | | | | |
| | | | | |
| | | | | |
| | | | | |
+------+------+----------------------------------------+-------+--------+
| Subtotal | 283.70 |
| Shipping | 10.00 |
+------------------------------------------------+--------+
| Total | 293.70 |
+------------------------------------------------+--------+
Thanks again for all the help, Elanor.
Please Ship to the following address.
Konrad J Hambrick
310 Third Avenue
Suite C21
Chula Vista, CA 91910
(619) 423-4451 (home)
(619) 585-8611 (work)
[email protected]
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@Neutronium95 --
I've looked at the link and the Cerakote C-7600 product line looks very interesting.
Please let us know how it goes !
Thanks !
-- kjh
EDIT:
@Neutronium95 --
When you mentioned Cerakote, I immediately thought of one of my rifles which is olive green which would get lost on the prarie.
Then I remembered this: Pink Cerakoted Billet AR-15 80% Lower Receiver
That wouldn't hide from me ! Time for me to look into Cerakote: SHOP CERAKOTE® COATINGS
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My order was basically the same, but with the addition of the the aluminum spray paint. I tried the 4525 expoxy for the first time, and I think it was basically a waste. It turns out that is the same epoxy as the 4461, but with some black pigment, and distributed into little jars where the part stuck to the lid throws off the mixture ratio.
I made pretty good progress today, and I didn't mess anything up. When I reviewed my class 3 application, I saw that I had promised to use redundant Blue Ravens not only for the sustainer, but also for the booster and 2nd stage, so I had some work to do to re-make those av-bays. Fortunately, I had already remade my booster av-bay recently in 2 parts, where the electronics is separable from the chute compartment. This is important because in order to go from a single Blue Raven/tracker combo to using 2 Blue Ravens, I needed to switch to the 29mm round Blue Ravens, which use 3 threaded rods rather than 4.
The booster and the 2nd stage are 38mm diameter av-bays, which makes the batteries less of a squeeze than the sustainer, which uses 29mm airframe tube for the av-bay in order to leave some clearance to the ID of the nosecone. The av-bays for the booster and the 2nd stage are each 2.50" long, and identical in interior configuration, other than adding airstart ignition connection for the 2nd stage.
Here is the difference in length needed to go from 1 original Blue Raven to two 29mm Blue Ravens.
I also made the motor anchor/air start screw switch:
I glued the switch and the wires down with some thickened epoxy that is curing now.
The booster and the 2nd stage are 38mm diameter av-bays, which makes the batteries less of a squeeze than the sustainer, which uses 29mm airframe tube for the av-bay in order to leave some clearance to the ID of the nosecone. The av-bays for the booster and the 2nd stage are each 2.50" long, and identical in interior configuration, other than adding airstart ignition connection for the 2nd stage.
Here is the difference in length needed to go from 1 original Blue Raven to two 29mm Blue Ravens.
I also made the motor anchor/air start screw switch:
I glued the switch and the wires down with some thickened epoxy that is curing now.
Adrian --
I am not sure I grasp the scale of your AV-Bay photos -- are those 29mm Blue Tube Couplers ?
Either way ( 38mm or 29mm ): Holy Cow ! Those are tiny !
Thanks for the post and the pictures and good luck with the next steps !
-- kjh
I am not sure I grasp the scale of your AV-Bay photos -- are those 29mm Blue Tube Couplers ?
Either way ( 38mm or 29mm ): Holy Cow ! Those are tiny !
Thanks for the post and the pictures and good luck with the next steps !
-- kjh
Thanks Adrian.
That's REALLY good to know because I spent a zillion 'bachelor bucks' gathering all the parts for my 98mm min diameter L3 "El Mui Grande Vulcanite" project back in 1998, including a Walston system and a complete RMS 98/10240 system along with that Cotronics stickum and enough Carbon and Kevlar fabric for a wrap or two from tip to tail.
I was looking at nearly mach 2 and 26K feet or so at Black Rock on the M1939 that I had planned to fly and I wasn't sure back in those olden days what would happen to the Hawk Mountain Glass and plain ole West Systems epoxy at such speeds for the 7-sec tBurn of the motor.
Mach 2 -to- 3 flights these days are, if not common, they're not rare either, but they were terra incognita back in those olden days.
My self-gathered 'kit' is still in the original ( opened, then resealed ) boxes after three cross-country moves over the past 25-years from San Diego to L.A. to Florida to Texas.
All the parts still looked fine back in April when I had to take a peek, even the end-grain balsa I bought for fin sandwich layups, but I will definitely need to replace the 'expired' Cotronics stuff.
I am going to build the rocket 'soon' (*) but I'll be trying to find something other than the Cotronics ceramics ( probably don't need it at mach 2 or even at mach 3 if I was to squeeze an O-motor into the fincan ...
Thanks for that info !
I am liking @Neutronium95's Cerakote idea after using a couple Cerakoted firearms and reading the specs and the application notes on their website !
And from what I've learned here recently, I think all my tip-to-tail fabric might be overkill.
I don't know any more if I'll ever make that L3 flight, but the rocket was light enough to fly J's and Ks at safe speeds and to respectable altitudes and who knows, maybe an M1969 is in the cards ?
Enough old fart reminiscing ... thanks again for the feedback Adrian and now back to your build !
-- kjh
(*) - Even though I may never do a Level 3 flight, I'll go thru the Level 3 TAP process 'just in case' I ever do it ...
Yesterday was a big day for me for rocket prep, since I needed to take everything to Steve Jensen by the end of the day for him to kindly drive out to Balls while I fly there on Thursday. That included head-end ignition mods to 2 forward closures, airstart and standard igniter preparation.
I'm using a new (for me) concept for airstart preparation. Since my airstart igniters on my 2nd stage and sustainers are buried in the core of my assembly, particularly for the sustainer, I'm going to install the motor grains at the away cell pad. When I tried this last year, the igniter got bent over and didn't go down into the core. This year, I have incorporated a guide thread with small nut for a weight that hangs down from the igniter, down the motor casing. When I install the motor grains that are glued into the liner, I'll drop the weight down the core first and then use the thread to gently pull the igniter into the core when the motor is fully seated. In test fittings, this worked like a charm.
Yesterday I also charged up all my batteries, put together the sustainer, 2nd stage, and booster av-bays and closed them up. I connected my booster av-bay to the chute holder, and did the final installation of the sustainer head end igniter, motor spacer, screw switch, av-bay, chute, and I adjusted the spacing of the nosecone ejector piston so that it pushes against the nosecone harness attachment hardware in the tip of the nose. I modified two trackers to use the latest magnetic switches, and tested my sustainer electronics. I think there were a few more things I had to do. Then I packed.
Some photos from the sustainer assembly:
Forward closure with igniter and guide thread installed:
On the motor case:
With motor spacer and the screw switch:
Av-bay baseplate bolted onto the motor forward closure, with the screw switch visible and the airstart connector poking out on the right
First Blue Raven about to be installed:
Second Blue Raven installed with aluminum 4-40 spacers:
A nut driver with a hollow shaft is super helpful:
Clearance between the forward motor closure bolt and the Blue Ravens: Two 4-40 small pattern nuts required.
Next the tracker goes in there, then the batteries, then the 29mm airframe tube I'm using to enclose the av-bay and support the chute cannon (sorry no photos)
I'm using a new (for me) concept for airstart preparation. Since my airstart igniters on my 2nd stage and sustainers are buried in the core of my assembly, particularly for the sustainer, I'm going to install the motor grains at the away cell pad. When I tried this last year, the igniter got bent over and didn't go down into the core. This year, I have incorporated a guide thread with small nut for a weight that hangs down from the igniter, down the motor casing. When I install the motor grains that are glued into the liner, I'll drop the weight down the core first and then use the thread to gently pull the igniter into the core when the motor is fully seated. In test fittings, this worked like a charm.
Yesterday I also charged up all my batteries, put together the sustainer, 2nd stage, and booster av-bays and closed them up. I connected my booster av-bay to the chute holder, and did the final installation of the sustainer head end igniter, motor spacer, screw switch, av-bay, chute, and I adjusted the spacing of the nosecone ejector piston so that it pushes against the nosecone harness attachment hardware in the tip of the nose. I modified two trackers to use the latest magnetic switches, and tested my sustainer electronics. I think there were a few more things I had to do. Then I packed.
Some photos from the sustainer assembly:
Forward closure with igniter and guide thread installed:
On the motor case:
With motor spacer and the screw switch:
Av-bay baseplate bolted onto the motor forward closure, with the screw switch visible and the airstart connector poking out on the right
First Blue Raven about to be installed:
Second Blue Raven installed with aluminum 4-40 spacers:
A nut driver with a hollow shaft is super helpful:
Clearance between the forward motor closure bolt and the Blue Ravens: Two 4-40 small pattern nuts required.
Next the tracker goes in there, then the batteries, then the 29mm airframe tube I'm using to enclose the av-bay and support the chute cannon (sorry no photos)
The teeniness of that av-bay is stunning.
After skipping ahead a few steps, starting from the bottom is the blue motor case, the white spacer with screw switch, the red av-bay housing with the tracker antenna poking out, then the carbon fiber chute cannon, then the nosecone ejector piston.
The little screw head at the very top pushes against the hardware that is embedded in the very tip of the nosecone to attach the nosecone harness.
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Today I made a replacement for the sustainer’s toroidal chute that is pretty beaten up and has gotten tangled in recent flights.
It and a piston and some shock cord fit into the 29mm carbon fiber chute cannon in the photo above.
It and a piston and some shock cord fit into the 29mm carbon fiber chute cannon in the photo above.
Looks great! Good luck on your flight. Wish i could make it out there this year.
I'm finalizing my plans for ignition settings, incorporating feedback from the class 3 analysis report and my build weights and flight results. The mass and dimensions came out pretty close to the initial predictions, so the plots on the first page of this thread are still valid. It turns out that the horizontal distance requirement for the FAA agreement is for the 3-sigma dispersion to be less than 80,000 feet radius. That's 15 miles, much farther than I would want the rocket to land because it would put a lot of unfavorable terrain in play.
5 miles in any direction will still be on the playa, and 10 mile landing radius will have a good chance of landing on the playa or in areas where retrieval wouldn't be too extreme. If I allow ignition at a sustainer angle of 12 degrees, that would put apogee about 10 miles away. But since the air is so thin if I get a good boost, the apogee deployment wouldn't slow down the apogee deployment for a while, so I should back off of that a bit and aim for a targeted ignition angle of 10 degrees. This is accomplished with the angle > future angle threshold setting, which is the angle estimated after a 3 second ignition delay.
There are four categories of initial flight angle with this ignition setting strategy
Category 1: Near-vertical boost. In this case, the angle is less than 10 degrees at sustainer ignition, and the trigger is altitude that corresponds to the optimal ignition altitude for a near-vertical flight. This is 29kft if I don't get any significant sustainer aeroheating damage. But if there is enough damage to correspond to turbulent flow for the whole flight, then 27kft would be the optimal ignition altitude. This is what I will pick for this case. This case will be covered by the primary set of deployment logic for channel 3 for my sustainer.
Category 2: Boost straight enough to want to delay until the target tilt at ignition. This will be triggered by the future angle exceeding 10 degrees. This will be the driver for the secondary logic for channel 3.
Category 3: Boost is pretty angled, so I want to fire the sustainer as soon as it's slow enough. The secondary ignition logic will also drive this case. In this case the ignition angle will be higher than the target angle, but less than the maximum safe angle. The dispersion analysis calculated that there was no initial angle that would violate the FAA horizontal limits, through 20 degrees, so that makes this category viable. Based on the simulated horizontal distance, I will set the maximum tilt angle at 16 degrees for this case, knowing that with a 2 second ignition delay, it could be 18 degrees. If I simulate that case, it takes a 10 degree initial angle to cause this, and the altitude two seconds before 18 degree pitch angle is right at 19,000 feet. This flight sims to 103 kft and the downrange distance at apogee is 50,000 feet (9.5 miles) This is the maximum initial angle coming out of the launch tower that I'll tolerate for a sustainer ignition. Thus I'll set the maximum tilt angle of 16 degrees, minimum altitude of 19,000 feet for the secondary logic case.
Category 4: The initial angle is so poor that I don't want to ignite the sustainer at all. If the rocket is tilted > 16 degrees and getting worse as it passes through 19,000 feet, it will be a 2-stage + dart flight, but I'll likely get the stages back to fly another day.
Next I'll figure out what I want for the limits of the 2nd stage ignition, but dinner comes first.
5 miles in any direction will still be on the playa, and 10 mile landing radius will have a good chance of landing on the playa or in areas where retrieval wouldn't be too extreme. If I allow ignition at a sustainer angle of 12 degrees, that would put apogee about 10 miles away. But since the air is so thin if I get a good boost, the apogee deployment wouldn't slow down the apogee deployment for a while, so I should back off of that a bit and aim for a targeted ignition angle of 10 degrees. This is accomplished with the angle > future angle threshold setting, which is the angle estimated after a 3 second ignition delay.
There are four categories of initial flight angle with this ignition setting strategy
Category 1: Near-vertical boost. In this case, the angle is less than 10 degrees at sustainer ignition, and the trigger is altitude that corresponds to the optimal ignition altitude for a near-vertical flight. This is 29kft if I don't get any significant sustainer aeroheating damage. But if there is enough damage to correspond to turbulent flow for the whole flight, then 27kft would be the optimal ignition altitude. This is what I will pick for this case. This case will be covered by the primary set of deployment logic for channel 3 for my sustainer.
Category 2: Boost straight enough to want to delay until the target tilt at ignition. This will be triggered by the future angle exceeding 10 degrees. This will be the driver for the secondary logic for channel 3.
Category 3: Boost is pretty angled, so I want to fire the sustainer as soon as it's slow enough. The secondary ignition logic will also drive this case. In this case the ignition angle will be higher than the target angle, but less than the maximum safe angle. The dispersion analysis calculated that there was no initial angle that would violate the FAA horizontal limits, through 20 degrees, so that makes this category viable. Based on the simulated horizontal distance, I will set the maximum tilt angle at 16 degrees for this case, knowing that with a 2 second ignition delay, it could be 18 degrees. If I simulate that case, it takes a 10 degree initial angle to cause this, and the altitude two seconds before 18 degree pitch angle is right at 19,000 feet. This flight sims to 103 kft and the downrange distance at apogee is 50,000 feet (9.5 miles) This is the maximum initial angle coming out of the launch tower that I'll tolerate for a sustainer ignition. Thus I'll set the maximum tilt angle of 16 degrees, minimum altitude of 19,000 feet for the secondary logic case.
Category 4: The initial angle is so poor that I don't want to ignite the sustainer at all. If the rocket is tilted > 16 degrees and getting worse as it passes through 19,000 feet, it will be a 2-stage + dart flight, but I'll likely get the stages back to fly another day.
Next I'll figure out what I want for the limits of the 2nd stage ignition, but dinner comes first.
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