Go Devil 38 L2 Cert Build

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Total weight = 539g, 1.11 lbs. Below is my current .ork file. The only thing off is the "eggfinder coupler" in the file. Not sure what happened there. I don't actually have the harnesses or chutes. These weights came with the "stock" .ork file. I also don't know the exact weight of the lower motor bulkhead.
The 539g comes from the manufacturer parts, plus the 3D tracking sled from shapeways and what I did to the fins...

Okay. SO much advice to ride friction fit. Would I have to epoxy a harness in?
If not then I assume I would have to use a threaded forward closure with an eyebolt?
If I don't place a bulkhead above the motor how do I ground test?
Should I just duct tape the end closed tight?:lol:
Honest question I really don't know.

Unfortunately I live in California and can't fly Loki. I'm not aware of any 38mm K motors I could use. If I didn't place a bulkhead I could potentially add a coupler and fly Loki out of state later...:confused: and the fins would for sure be beefy enough...
To be completely honest in a way I wish I didn't add a ply. But I'm living with it.

Mine came in at 1.875 lbs (30ozs) and I didn't do T2T. I used a slimline retainer for motor retention but now wish I had got with Cj's method. I would go with shear pins for sure.
 
Mine came in at 1.875 lbs (30ozs) and I didn't do T2T. I used a slimline retainer for motor retention but now wish I had got with Cj's method. I would go with shear pins for sure.

So if I keep it under or around 30oz then I'm probably looking good.
Have you launched yours? If so what motor and flight data #'s?
I think I am going Cjs way. I'll just have to be particular during ground tests to execute the exact same steps for flight.

I would fly at FAR but I would have to fly there more frequently than other places I fly to make the hardware purchase worth while. Far is actually right up the road. (Comparitively speaking. Everything in the desert is "right up the road" within an hour)
 
I have flown mine about 4-5 times now. My 1st couple flight were on Loki H loads to around to 3K to see how the recovery worked out. I settled on a 30" thin mill chute with a 4" spill hole. Don't know the maker. At Airfest I flew it on a H45 and that didn't go too well. The motor lit but it sat on the pad and fizzled for about 3 seconds and slowly lifted off, cocked hard into the wind at about a 45 degree angle, high speed deployment severed shock cord. I recovered the sustainer but couldn't find the booster section but luckily it was found the next day and I just got back so the rocket is whole again. Next flight planned is in two weeks on a Loki I405 to around 7300'
I recently picked up a Go Devil 54 that I'll be building over the winter. I may try my hand at T2T on that one.
 
Unfortunately I live in California and can't fly Loki. I'm not aware of any 38mm K motors I could use. If I didn't place a bulkhead I could potentially add a coupler and fly Loki out of state later...:confused: and the fins would for sure be beefy enough...
To be completely honest in a way I wish I didn't add a ply. But I'm living with it.

Can't fly K's without a longer sustainer/fincan. Not enough room for the case. Kurt
 
Can't fly K's without a longer sustainer/fincan. Not enough room for the case. Kurt

I would epoxy a coupler and extra sustainer length for the cute. BuT, not going to. Unless Loki does some amazing things in california
 
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I would epoxy a coupler and extra sustainer length for the cute. BuT, not going to. Unless Loki does some amazing things in california

The easiest would be to start with a longer sustainer tube like another fellow did. He knew upfront it was too short and asked for a longer tube from RW. If I had been aware of that, I probably would have paid for a longer lower and upper bay tube.
I'll weigh mine again and post it. I have it loaded and ready with a J500 so I can remove the motor and get an all up weight.

Kurt
 
If you have room for an Aeropack or similar go for it. That said, I have seen one of the epoxied on ones come off in flight- once.

This is the style of motor retention I prefer. I make my own and include an eyebolt to attach it up the airframe to the avionics bay with a small harness. Yet to have one come loose, but prepared in case it does :)

To reduce the chance of the epoxy shearing under thrust (possibly exascerbated by different Cte of fiberglass and Al) I glue a short length of coupler just above the mount to help take the shear stress. This is in addition to a safety factor for the bond area of the MM of 1.5 (at peak thrust of most savage motor that will fit!). Here is a 98mm example on my Nike Smoke:
MotorMountGlued.jpg
 
Nice. Looks like threaded rod with an eyenut? You epoxy or threadlock the eyenut to keep it from coming unscrewed? Why the holes if motor ejection is not involved? Is that for lightening purposes because such a large chunk for 98mm is pretty
heavy? If you're worried about the epoxy, do a project some time with Cotronics 4525 and use it for that type of motor mount above. Pretty heat resistant. Proline 4500 is "supposed" to have similar heat characteristics but it's not guaranteed.
Kurt
 
Nice. Looks like threaded rod with an eyenut? You epoxy or threadlock the eyenut to keep it from coming unscrewed? Why the holes if motor ejection is not involved? Is that for lightening purposes because such a large chunk for 98mm is pretty
heavy? If you're worried about the epoxy, do a project some time with Cotronics 4525 and use it for that type of motor mount above. Pretty heat resistant. Proline 4500 is "supposed" to have similar heat characteristics but it's not guaranteed.
Kurt

Looks like an eye cast onto a bolt to me. So a heavy duty eye bolt? I hope the holes are just so it looks cool.
 
Definitely because the holes make it more aerodynamic ;)

The easiest would be to start with a longer sustainer tube like another fellow did. He knew upfront it was too short and asked for a longer tube from RW. If I had been aware of that, I probably would have paid for a longer lower and upper bay tube.
I'll weigh mine again and post it. I have it loaded and ready with a J500 so I can remove the motor and get an all up weight.

Kurt

I suppose IF I were to extend the airframe I should using countersunk screws.
To be honest I'll most likely not even bother with it. Odds are I buy another 38mm MD rocket capable of a longer motor case. Good enough excuse to buy another rocket.
 
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Definitely because the holes make it more aerodynamic ;)



I suppose IF I were to extend the airframe I should using countersunk screws.
To be honest I'll most likely not even bother with it. Odds are I buy another 38mm MD rocket capable of a longer motor case. Good enough excuse to buy another rocket.

Don't sweat it. You'll go plenty high on a J. Then again, you may end up sweating it if the positions don't come streaming in when you expect them. Happens to me just about every time with out of sight flights. I get antsy until that position comes
in with a valid GPS altitude when the clock shows the rocket is near or past apogee. If nothing received, either the tracker died, the range is not what it should be or the rocket is coming in ballistic. If DD, you might hear the Main deployment if it's
not a total deployment failure and see the smoke as the main harness is sliced by the upper bay if glass or zippers the heck out of the cardboard.

Make really, really sure your tracker installation and power supply is competent to stand up to the G's so it stays reliable. I see you have a good carrier and that's smart. If one press fits, the antenna could get smushed or break off the board and
it's bye-bye time. Kurt
 
Looks like threaded rod with an eyenut? You epoxy or threadlock the eyenut to keep it from coming unscrewed?

Correct on both counts. Only had an eye nut. Loctite bonded to a stud on the MM. Centre-punched on the end to prevent removal also.

Why the holes if motor ejection is not involved?

Correct again. Swiss-cheesing was only to reduce the mass, although a few people have commented that it looks cool. Anybody who knows me will know that I rarely do anything just for cool factor or fickle fashions :)

As for using a different epoxy, I would do the same whichever epoxy I used.
 
Correct on both counts. Only had an eye nut. Loctite bonded to a stud on the MM. Centre-punched on the end to prevent removal also.



Correct again. Swiss-cheesing was only to reduce the mass, although a few people have commented that it looks cool. Anybody who knows me will know that I rarely do anything just for cool factor or fickle fashions :)

As for using a different epoxy, I would do the same whichever epoxy I used.

Thanks. The coupler for "jamming" to relieve the shear stress is an excellent thought. If I'm doing a heavy conventional recessed ebay without an external switchband to take the load, I'll epoxy a coupler on the forward end of the sustainer to take the
thrust load. With remote activation of electronics these days, can do a clean look without external switches or excess access ports. Kurt
 
Wanted to follow up with the thread. I think I'm going to load my basket with eggs. Quantum eggs and finding eggs.
I've been looking for batterries.
Of course the eggs want a 250mah 7.4v. I'd like to give them at least300mah. Can I do it in this rocket?

My measurements say it can but it'll be reallyclose.

Do I have to have to get black powder. Are their black powder substitutes I can I use? Which ones?

Any thoughts?
 
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Wanted to follow up with the thread. I think I'm going to load my basket with eggs. Quantum eggs and finding eggs.
I've been looking for batterries.
Of course the eggs want a 250mah 7.4v. I'd like to give them at least300mah. Can I do it in this rocket?

My measurements say it can but it'll be reallyclose.

Do I have to have to get black powder. Are their black powder substitutes I can I use? Which ones?

Any thoughts?

I have a 2200mah that will fit in a future 38mm rocket I plan on building. I think you are fine on batteries, though as you note, fitment is never certain until you have parts in hand.

Powder is a major pain. When do you plan on launching?
 
I have a 2200mah that will fit in a future 38mm rocket I plan on building. I think you are fine on batteries, though as you note, fitment is never certain until you have parts in hand.

Powder is a major pain. When do you plan on launching?

Looking at the battery dimensions online is what has me weary to purchase two lipos just to have them be too big. Does the brand really matter much?

I would like to launch as soon as humanly possible. I do contract work and started a new job. My time to build and gather parts has taken a serious hit. Along with the wife and kids...
That being said I'll miss this months the launch in Lucerne for Roctober so I'd say November

Pending ground tests
 
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For years my go to for small lipo batteries has been Hobby King. If it's in stock in their warehouse, it's usually 3 days from 'click' to delivery for me. Their house brand of battery is robust enough to handle VERY poor landings in RC planes and rockets, great form factor, and they're cheap enough to be disposable at the end of a flight season. I charge at 1C, and I have never had one get hot or swell on me.

For 2S flight batteries I fly these in both my EggFinder TX and flight computers:
https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=59263

For 1S flight batteries I fly both of these:
300 mah https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=88956
750 mah https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=59260

Losi JST DS style connectors for the above batteries:
https://www.ebay.com/itm/252417911086

If you want to replace the connectors with the red JST style:
https://www.hobbyking.com/hobbyking...tail_10cm_Length_10pcs_bag_AR_Warehouse_.html

Banana plugs to make a charge harness from the above 1S connectors:
https://www.ebay.com/itm/331558288961

If you want to stay with the red JST connectors:
750 mah https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=44082

For a tracker battery, I use this for my EggFinder in the handle of the 3D printed case:
https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=59281

I charge with this charger powered from any generic 12vDC power supply:
https://www.ebay.com/itm/iCharger-1...043233?hash=item210fdcb4e1:g:-8gAAOSwU1FXP~6Y
 
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Thanks Banzai!
Thank you very much! You have literally just saved my day!
Amazon wasnt offering anything close to what you have suggested that I had noticed.
 
The battery I've mostly standardized on is this one, though in my Go Devil 38 I found a battery that is just a tad slimmer (and 900mAh instead of 950, this one) so it eases the fit just a bit. I fly one in the avionics bay with my SLCF and one in the nose for my Eggfinder TX. The only other battery style I have is a single 1800mAh 2s for my Eggfinder LCD (didn't use the same JST connector, so I cut off its smaller leads and soldered on a set of JSTs, and cut off the heavy-duty leads entirely, taping them off). I did just kill two of my 950's when my Osprey 75 crashed at XPRS, so it's probably time to order a few more. :p Plus I just built a second EF LCD, so I could use a second one of those batteries also.

With the printed sleds I'm using now I could probably go back to the Turnigy 950mAh everywhere, but I have 3 of these Tenergy 900mAh's, so I figure I'll keep using them in the Go Devil 38 at least.
 
Thanks Banzai!
Thank you very much! You have literally just saved my day!
Amazon wasnt offering anything close to what you have suggested that I had noticed.

No issue. I should also add that I've flown those batteries 1S and 2S on the RRC2, RRC3, SLCF, and Eggfinder Quark. Just watch your resistance on the matches and how much current you're going to be putting through your computer's deployment channels.
 
Electronics are in the mail. Until then,

[video=youtube;73tGe3JE5IU]https://www.youtube.com/watch?v=73tGe3JE5IU[/video]
 
Eggtimer came on friday. I went to Roctober on Saturday and church all day today leaving me with zero time to even open the packages. I feel like as soon as I open them I need to at the least be ready to keep track of tiny parts.

On a side note I was able to meet Cris Cerving and the folks from Madcow at Roctober. Yep. That was pretty cool.

Anywho I'll post an update once I begin soldering. I'm shooting for the 19th of November at FAR.
 
It wouldn't feel right to drop on a build thread.
I don't have a whole lot to report though. I've decided not to solder the eggtimer electronics myself. Believe it or not a gentlemen on the nearby Air Force Base got excited about it and is doing it for me for free. At least this way someone who does it for a living will build it the right way. He said he would have it ready on Monday.
Of course more to come.
 
Good that you got someone to assemble it for you, but you have missed out on the fun! Consider giving it a go yourself next time. You will probably find it easier than you thought.

I suppose after reading through the eggtimer support pages several times the biggest thing that stuck out to me was the recommend to not make eggtimer a first soldering project rather buy a spark fun and practice their, first.
I wasn't so worried about not being able to do it and get it to work. Im more leaning on the idea of keeping it working with quality solder joints. I imagine rocketry electronics need to take a relatively large amount of abuse.

No doubt I will solder my own future electronics
 
Alright you guys. This is what it's looking like as of now. The eggfinder is almost complete. Not sure exactly what happened to the processor for the receiver but it is missing. Cris is already sending out another. I need to solder the antenna for the transmitter. Wasn't sure if I wanted to place an edge connector or not but for now I think it'll be fine "stock"

I'm still working hellish hours but now the electronics are near done I'll keep on truckin.

VZM.IMG_20161019_052248.jpg20161018_200400.jpg
 
20161019_192346.jpg

This is the quantum. Do you guys think I should remove the main and drogue blocks and solder wire from the quantum and into the forwad aft bulkheads?
What is most reliable here?
I also was thinking I'd just solder a wire with a connector for the lipo into the battery position also. Same with the eggfinder in the nose cone

The processor already came for the eggfinder recieved also. I'll get that fully functional very soon. Picking up hardware in town today.

2x 3/16 all threads
5-64 shear pin
Set screws
1/4" eye bolts
 
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With screw terminal blocks, if the wire breaks you can just strip it back and effect a field repair. If it's soldered in and it breaks in the field during pre-launch, you're going to go looking for a soldering iron, solder, and a place out of the wind and cold to repair it. Soldering the battery harness is less common, but probably OK seeing as it gets less flex and messing with on the sled.
 
View attachment 303733

This is the quantum. Do you guys think I should remove the main and drogue blocks and solder wire from the quantum and into the forwad aft bulkheads?
What is most reliable here?
I also was thinking I'd just solder a wire with a connector for the lipo into the battery position also. Same with the eggfinder in the nose cone

The processor already came for the eggfinder recieved also. I'll get that fully functional very soon. Picking up hardware in town today.

2x 3/16 all threads
5-64 shear pin
Set screws
1/4" eye bolts

I would remove all the screw blocks and solder the wires for a few reasons:
  1. Those screw terminals are smaller than standard. In practice they were MUCH harder for me to secure a good wire connection in comparison the terminals on other altimeters like the stratologger.
  2. The wire soldered connection is far more robust than the screw terminals. You've basically eliminated a failure point because the wire won't work loose without breaking.

The downside is portability. However, if you make the decision now to standardize wire harnesses across your entire fleet you can make it portable.
 
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