Nomex honeycomb Fin skins on AMW Der Red Max build

Looking forward to seeing this one live Chris.

rharshberger said:

Looking forward to seeing this one live Chris.

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Thank you, Rich. A few more things to wrap up, but it is most of the way finished.

Looking forward to the May launch!

Chris_H said:

Thank you, Rich. A few more things to wrap up, but it is most of the way finished.

Looking forward to the May launch!

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I'm looking forward to the May launch myself, its been a bit to long since the weather allowed us to fly (first weekend of March was our last launch), the May launch is going to be extended to include FAR 101 flying on Friday and possibly Sunday (if we have enough people planning to stay and help with tear down on Sunday, otherwise the event ends Saturday evening), the FAA Waiver will be in place for Saturday and maybe Sunday. I have a two stage project and several other builds to fly.

The Av bay is almost finished, only a few more small details, like sealing around where the wires pass through the bulkhead, glue on the lower bulkhead, and a few other details. There are 4 static ports in the switch band, 2 at .100", and 2 at .125".
The USB cable for the Marsa data port plugs right through the lower bulkhead, accessible when the lower lid of off.

Where the ejection wires pass through the bulkheads, the twisted wire pairs were smeared with an adhesive sealant, then covered in heat shrink. The holes in the bulkheads were a tight slip fit, and will be sealed on both sides of the bulkhead, in order to keep ejection gasses away from the electronics.

The wiring is all silicone jacketed, everything tinned, and all JST connectors soldered and clean.

The UHF antenna is in the nosecone rather than facing down which would have had it in free air at apogee. I did this because when a 54mm 6G Xl motor is in it, the antenna would have been compromised if it were facing down. I am about to find out how much signal loss comes from the black fiberglass nosecone, hopefully not too much. There will also be an RF tracker on board.

The rest of the rocket is pretty close to being finished. The main work will be in finishing the fins in catalyzed polyester. It is a really cool finish that is almost as tough as epoxy, and will 'cut flat' and polish just like a piano finish. The fins are looking beautiful right now. Naked CF and great curves. Until they eat the first rock....

If anyone knows of better terminal blocks for the matches, and is willing to share, please post a link. These work, but I don't really like them, I know there are better. These should work for now.

Have you considered ditching the terminal blocks altogether, and simply using a JST connector for ematch termination? Yes, it requires that you crimp on JST connectors to your ematches, but it makes switching out ematches that much simpler...

-Robert

rhildinger said:

Have you considered ditching the terminal blocks altogether, and simply using a JST connector for ematch termination? Yes, it requires that you crimp on JST connectors to your ematches, but it makes switching out ematches that much simpler...

-Robert

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I have considered that, especially for the nosecone. And also, wiring the matches in to the altimeter directly. I may change things up, not sure.

Or ditching the terminal blocks all together and wiring directly to the altimeter by passing the wire throu a hole in the bulkhead and either sealing it with poster tack or a well-nut ( aka rawl nut). Its one less connection to worry about being faulty.

All my ematches are wired diectly to the ematches, it does however require dis assembly of the avbay to prep for another flight.

I had 2 concerns that I had not yet worked through in regards to wiring directly to the altimeters. One is that a strain 'clamp' of some sort would be necessary, maybe just a loose knot in the wire with enough slack to protect the altimeter, and 2, that because of the tight quarters in the bay, and the terminal blocks of the Marsa being right up against the satellite ring, routing the back-up charges from the Marsa would be a little more convoluted. I may still do this. Right now, I feel pretty good about this current setup, and need to be on to finishing up the rest of this bird, and doing some ground testing, as there is a launch coming up in less than 2 weeks. If I change the match terminations, it will be after I complete the rest of the preparations. Meanwhile, this subject is definitely on my mind. I suppose that even just wiring in the main charges direct, is a step up in reliability, and would be easy to do.

I do appreciate critique, and suggestions, so, thank you.

The fins are now completed and polished. The finish is catalyzed polyester, basically polyester resin. After the carbon laminations were sanded and cleaned, 3 coats of polyester was sprayed. This is a professional finish system and definitely not recommended for non professional finishers. That it contains polyisocyanates is enough of a part of the reason why not. It is sprayed 15-20 minutes between thick coats. By the 3rd coat, everything is looking glossy. The next day it was blocked with 80 grit on a wood block, it is that thick. Followed by a wood block with 220, then a rubber block with 400, 600 on a DA, 1000 on a DA, 1000 on a rubber block in the corners. After that, 3000 grit Trizact is used. If you are ever doing a polished finish, check out 3M 3000 Trizact, as it is a magic abrasive, and a huge time saver. Not to mention that it leaves a fantastic result. This was followed by 3M Perfect-It compounds on a 3" mini polisher with a yellow foam head. If this were a piano, I would have taken it to absolute perfection, but it is not, so I stopped early, and it is very good, considering that it is a rocket that will see slightly over mach 1 at best. Time for the next project!

A few notes on the fin construction. Before the leading edges were filled with Kevlar fiber, they were profiled to a very sharp edge with a sanding block. Then, the exposed honeycomb as well as the skin of the honeycomb was very lightly sandblasted with 180 grit Aluminum oxide in order to give a little more tooth for the kevlar filler. I tested the materials prior to putting the airframe in the blast cabinet so the pressure was correct, and I had a sense of how the process feels. My thinking is that the edges of the fins are likely to connect with nasty things like rocks, and I do not want the underlying honeycomb damaged. Kevlar is tough stuff, and I wanted maximum strength in the kevlar fill. It took 3 fill coats to get it completely filled and completely faired. Sanding the kevlar fill was not easy, but it does sand. I have a powerful down draft sanding table to capture the dust before it becomes airborne.


These fins feel super stiff, and very tough. I wish I knew how to sim them in one of the fin flutter calculators, though for this rocket, I think it does not matter, they feel plenty strong to take any motor that will fit.

For now, the fin can is ready to install the lugs and the recovery harness, and fly. I will probably paint it later, after it has flown.

Those fins look almost too perfect, almost like a computer generated graphic. Good job!

Polish the body and dont paint it at all, nice job.

Those fins are beautiful! Nice work

rharshberger said:

Polish the body and dont paint it at all, nice job.

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I agree with Rich on this one.

That looks so fantastic. I need to finish mine, clear coat and polish it, but it will be a poor imitation of this beauty.

rharshberger said:

Or ditching the terminal blocks all together and wiring directly to the altimeter by passing the wire throu a hole in the bulkhead and either sealing it with poster tack or a well-nut ( aka rawl nut). Its one less connection to worry about being faulty.

All my ematches are wired diectly to the ematches, it does however require dis assembly of the avbay to prep for another flight.

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+1 to this idea. I do this, but use etc silicone instead of poster tack.

Thanks for the kind comments.


Mark, what kind of silicone do you use for sealing the wires if they are wired direct to the altimeter and are changed every filght? Did I misunderstand you? Seems like silicone caulking would need to cure, or else it would be a mess.

I definitely do not like these terminals, and may remove them prior to the first flight. I have been doing some testing, and they seem like a 'replaceable part' at best. They do seem secure enough, but...

I had thought of polishing the raw fiberglass tubing, but the airframe is thin wall, and the manufacturing scratches from when the tubes were sanded smooth are acutually pretty deep. In order to get below these, at least 0.005" would have to be removed. As this tubing is already on the thin side when compared with how obust the rest of the rocket is, I think polishing it is a no-go. Anyway, if I paint it, I would like to do the lower section in a candy apple red over a big gold flake. In order to maintain RF transparancy, I think I might (if I paint it) do a flame job on it, with the 'flames' over a white base to give the brightness needed to look awesome, and have the flames going down into the candy apple red, and at the same time, allowing a window for the GPS and UHF antennae. Probably some marbling in the flames as well. I like to paint, but my time is also limited for how far I can go with it. If it flies well and comes home, it will get painted. Definitely not before the first launch, which is hopefully in 10 days.

I will probably wire direct to the altimeter.


Currently, I am trying to figure out how to calibrate the altitude on the Aim unit. It is reading 1900' ish, and the Marsa is reading 2300. I think they both need to be reading the same altitude, otherwise the main deployment altitude will vary between the 2? The outputs seem to be working in vacuum tests. The Marsa is having difficulty popping the main deployment, but I think that is because the deployment altitude is set below the actual altitude at this location, so I have to trick it by very suddenly releasing the vacuum, and then sometimes it misses. Pretty sure this has to do with the altitude calibration. So much to figure out, and she cannot fly until it is all clear. Extensive deployment and tracker testing will happen this weekend.

Chris_H said:

The Marsa is having difficulty popping the main deployment,

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What do you mean? There are LED lights next to the output of each channel. Are you saying the main channel doesn't fire when vacuum is slowly released OR does the channel fire but the ematch doesn't ignite?

Chris_H said:

but I think that is because the deployment altitude is set below the actual altitude at this location, Pretty sure this has to do with the altitude calibration.

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No. The Marsa deployment altitude is the measured altitude from the measured ground altitude.

Send me a PM or email if you have any other questions to help you resolve issues you are seeing.

Regards,
John

jderimig said:

What do you mean? There are LED lights next to the output of each channel. Are you saying the main channel doesn't fire when vacuum is slowly released OR does the channel fire but the ematch doesn't ignite?




No. The Marsa deployment altitude is the measured altitude from the measured ground altitude.

Send me a PM or email if you have any other questions to help you resolve issues you are seeing.

Regards,
John

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Thank you., John.

I am sure the unit is working correctly, I just need more time with it. User error, almost certanly. I could not view the LED's, as it was in the AV bay, sealed up. The selected channels are all firing, but with my crude setup, I was not getting consistent results. I need to come up with some kind of vacuum chamber with a clear lid, and I will this weekend. I did confirm that everything *might* be working correctly., which is better, at this point, than anything not working at all.

You may hear from me in the next couple of days, as I may have a question or 2.

Cheers!

There is another source for the Nomex Honeycomb. https://store.acpsales.com/categories/334/panels-sheets-laminates
ACP has several different thicknesses and some panels that have the coverings already bonded to the Nomex. At one time they had some available as factory seconds for a reasonable price, not so much any more. I still think it is worth a look though.
Your fins look great.

Here is the recovery harness. The 24' main harness is 1/2" tubular nylon. The lower anchor is 1" flat kevlar webbing which passes through 1/4" holes in the 2 centering rings, secured with a square knot at the aft end of the motor mount, enabling easy replacement, and some protection from zippering. The drogue harness is attached to the kevlar anchor point with a cow hitch, secured with a figure eight knot. The 1/8" kevlar drogue lead is secured to the main harness with a clove hitch with an extra pass through to prevent slippage. The harnesses attach to the AV bay with a small steel 'locking 'biner', to 3/8" tubular kevlar loops, tied with a double fisherman's knot, and secured to double stainless M5 eye-nuts at each end, in an 'equalized configuration, to equalize pull on each eye, minimize shock, and to provide redundancy. The kevlar harness pieces are 'whipped' with painters pinstriping tape to prevent fraying. An RF tracker is tied to the drogue harness. The drogue chute is a 15" Fruity Chutes elliptical. The 24' main chute harness is constructed similarly. The main chute is a 48" Fruity Chutes Iris Elliptical, in a Fruity Chutes deployment bag. The pilot chute is a Fruity Chutes 12" elliptical. The attachment point in the nosecone is a loop of 3/8" tubular Kevlar that is secured to a 1/4-20 hex head bolt that threads into the aluminum nosecone tip with a clove hitch. The nomex blankets are just squares of nomex, cut from a piece which was purchased off ebay for a great price.




The design of the Aero-pac tailcone relies on a precise dimension for the aft motor closure height, combined with a spacer. I set the one on this rocket for a CTI 54mm closure, and had to make a special spacer for the 38-54 adapter with one of my AT aft closures to achieve a precise fit, and will probably need to make another spacer for Aerotech 54mm hardware. Otherwise, either the motor is not well secured, or there is a gap between the aft end of the airframe and the upper lip of the tailcone retainer.

Thanks to Rich, and Dave, and the fine folks of the Tri-City Rocketeers for putting on a great launch this past weekend!



2 successful launches of this rocket. One on an AT I600 Redline, and one on an AT J350 White Lightning.

Congrats on the cert process!

Thank you, Rich!

Congrats on an amazingly well-done build and on two apparently excellent flights. Were their any issues with the recovery from either flight?

BDB said:

Congrats on an amazingly well-done build and on two apparently excellent flights. Were their any issues with the recovery from either flight?

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Thank you.

The flights were smooth and straight up, no spinning. On the first flight, I gave in to the impulse to go a little heavy on the deployment charges, so the shock from the first deployment also popped the main chute, likely from shearing the 3 2-56 plastic screws securing the sections together. It was only at 2100', so the rocket landed sitting straight up on the ground about 300' from where it launched. The second recovery went as it should have. Apogee drogue deployment at about 2200', main chute deployment at about 700'. Lesson learned.... stick with exactly what the ground test results yield. I did extensive testing in the days prior to the launch.

Before the next flight, I am moving to 4-40 plastic screws, and re-doing the ground testing. I am planning more flights on similar sized motors until I see that I actually have consistent deployment, then doing some ground tests with a 54 6GXL dummy in it, as that motor extends well into the donut AV bay, and then taking it up to the 5000'ish altitude, and then up on a L935 Imax to around 9000' and maybe just over mach 1.

Here is the scene of the second flight landing.

Chris_H said:

Thank you.

The flights were smooth and straight up, no spinning. On the first flight, I gave in to the impulse to go a little heavy on the deployment charges, so the shock from the first deployment also popped the main chute, likely from shearing the 3 2-56 plastic screws securing the sections together. It was only at 2100', so the rocket landed sitting straight up on the ground about 300' from where it launched. The second recovery went as it should have. Apogee drogue deployment at about 2200', main chute deployment at about 700'. Lesson learned.... stick with exactly what the ground test results yield. I did extensive testing in the days prior to the launch.

Before the next flight, I am moving to 4-40 plastic screws, and re-doing the ground testing. I am planning more flights on similar sized motors until I see that I actually have consistent deployment, then doing some ground tests with a 54 6GXL dummy in it, as that motor extends well into the donut AV bay, and then taking it up to the 5000'ish altitude, and then up on a L935 Imax to around 9000' and maybe just over mach 1.

Here is the scene of the second flight landing.

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Picture perfect landing area. Where are you so lucky to fly?

This is one of the landing options at the launch area where the Tri-City Rocketeers launch from, close to Tri-Cities, Washington.

Chris_H said:

This is one of the landing options at the launch area where the Tri-City Rocketeers launch from, close to Tri-Cities, Washington.

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The other options we have are, tall grass/wheat between the 4 circles of sod, a little bit of sage brush, to the east, and later in the year a rocket eating cornfield about a 1/2mile the northwest. Most recoveries are in the Barefoot Recovery Area though. Rarely does the irrigation canal become a possibility due to prevailing winds. We have a great facility and awesome landowners who are very supportive of our hobby and other hobbies like ultrlight fliers and R/C sailplane clubs. Check out our facility using google earth the links are available on the club website which I believe is in my sig line.

Click in the black space for a video.