Looking for reccomendations for a 38mm MD

A fellow rocketeer is looking to build a 38mm MD rocket which will meet the following criteria:

- dual deploy
- 8" altimeter bay to accommodate Eggtimer TRS
- min 27" booster section
- FW/FG or suitable airframe for trans/supersonic velocities

Thank you in advance for your opinions.

Mike

mpitfield said:

A fellow rocketeer is looking to build a 38mm MD rocket which will meet the following criteria:

- dual deploy
- 8" altimeter bay to accommodate Eggtimer TRS
- min 27" booster section
- FW/FG or suitable airframe for trans/supersonic velocities

Thank you in advance for your opinions.

Mike

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You should look at a Mariah 38 from Giant Leap Rocketry. I have built one, but have yet to fly it. The av bay is tight, but might work. There is some room in the nosecone. You might think about drogue less for the DD aspect. There is a fiberglass and non fiberglass version. I will check mine and the specs that you requested. You might also try a Blackhawk 38 from Wildman.

Another good one is Public Missiles Cirrus kit.
Mr. Bob
Countyline Hobbies
Grovertown, IN.
574-540-1123
[email protected]
www.countylinehobbies.com

4kids49 said:

You should look at a Mariah 38 from Giant Leap Rocketry. I have built one, but have yet to fly it. The av bay is tight, but might work. There is some room in the nosecone. You might think about drogue less for the DD aspect. There is a fiberglass and non fiberglass version. I will check mine and the specs that you requested. You might also try a Blackhawk 38 from Wildman.

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Hi 4kids49, I hope for your sake that doesn't mean you have 4 kids @ 49, I have 5 year old twins at 48 and they are killing me.

I have the Mariah as well, although this recommendation is for a friend. My Mariah is still in progress and I do like the concept and quality of the build however there is no way he can use the Eggfinder TRS in the itty bitty shotgun tube so unfortunately it is out. The Blackhawk is on the list though...thanks

Blackhawk 38 only has a 6" AV-bay & a 16" payload & 32" booster.

bob jablonski said:

Another good one is Public Missiles Cirrus kit.
Mr. Bob
Countyline Hobbies
Grovertown, IN.
574-540-1123
[email protected]
www.countylinehobbies.com

Click to expand...

I have a PML Bull Pup and love it. I looked at the Cirrus, however it isn't dual deploy out of the box which is part of his criteria. I am also not sure of the length of the booster section, it says 44" overall with a 7.5" payload bay that leave 36.5" for the booster and nosecone. I am guessing the nosecone is somewhere between 6-8" so 27" may be close.

timbucktoo said:

Blackhawk 38 only has a 6" AV-bay & a 16" payload & 32" booster.

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I am guessing that it should be easy to get a 8" bay. The payload and booster more than adequate lengths.

mpitfield said:

Hi 4kids49, I hope for your sake that doesn't mean you have 4 kids @ 49, I have 5 year old twins at 48 and they are killing me.

I have the Mariah as well, although this recommendation is for a friend. My Mariah is still in progress and I do like the concept and quality of the build however there is no way he can use the Eggfinder TRS in the itty bitty shotgun tube so unfortunately it is out. The Blackhawk is on the list though...thanks

Click to expand...

Hi mpitfield,

Don't worry, I'm not 49, just a mere 56! Try coaching for 6 months a year and see how much flying time that you get! I can't even count all of the individual events from Cub Scouts, Boy Scouts, swimming, Little League Baseball, basketball, high school baseball and water polo, then add on school etc. I have a 5 year old daughter. I still don't have her activities up to speed yet. All good though. Rocketry helps keep me sane! Anyway, even if the Blackhawk 38 only has a 6 inch av bay, you can easily fix that with a slightly longer av bay tube, and maybe some longer all thread. Would definitely keep it in mind. Don't know much about the PML kits. I am really dying to fly my Mariah 38. It has been built for some time. I believe in ball parking things and then honing in on the final product. You might be able to get creative with the M38 av bay and an antenna going into the nosecone or something. I am not familiar with the Eggfinder specifics. Good luck though.

Building my own with LOC tubes and the Aeropack minimum diameter bulkhead/screw in the motor retainer. Four plywood fins that are glassed on the tube (old school) Upper bay will simply have a "hollowed" nosecone that has the shoulder end cut off so the EggFinder TRS can project its antenna into the nosecone.
Will use an Archtype cutter to deploy the main. Two small electrical/ematch terminals epoxied to the bulkhead/coupler. I'm going to reinforce the coupler so I can attach it with 4 small screws to the aft end of the altimeter bay so it's easy to connect the terminal wires to the TRS and use a Featherweight screw switch to activate the pyro circuit through the static port. Cheap and easy 'cause I've had the parts lying around for so long. J350 should get some really high altitudes. Supersonic cardboard tubes I say. Kurt

Why an 8" av-bay for an altimeter only 3.9" long? Use Lipo batteries and it will all fit in 6" without too much fuss.

timbucktoo said:

Blackhawk 38 only has a 6" AV-bay & a 16" payload & 32" booster.

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Wildman is happy to alter dimensions on their kits. Just let them know. Will cost a couple of extra bucks as you'd expect, but you get exactly what you want.

Edit: oh yeah, new kits should be in the new thin wall tubes, too.

Wow, lots of 38mm MD going on in the forum.

I just did the Wildman Black Hawk 38 kit. Tough as nails. The included epoxy is good stuff. I squeezed my existing altimeter (Perfectflite MAWD) into the 6" coupler, which was a PITA. I then built a little payload bay + nose cone volume to house a BRB900 and its antenna. No retainer, no buttons, so I had to build a tower for true MD performance. It survived a 6XL J to 12k' and Mach 1.4. I am learning that these long skinny rockets can have dynamic stability issues, so give yourself extra Cp/CG margin and plenty of launch guide.

If I did it again, I would get a 3D printed sled from Landru/MWC. Wildman includes fin guides, which is cool, but I found them a little too wiggly. I like my foam-core home made fin jig a little better.

Buckeye said:

Wildman includes fin guides, which is cool, but I found them a little too wiggly.

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That's interesting. I'm currently building a BH54 and my guides are too tight and I'll have to open them up a smidgin.

I will second Mariah38 from GLR.

Give me dimensions of electronics and i will measure if it fits into Mariah AVbay & nosecone (it's hollow).

MD tend to fly high, I assume you also plan on tracking devices?

matthew said:

That's interesting. I'm currently building a BH54 and my guides are too tight and I'll have to open them up a smidgin.

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I have BH54 fins and guides. My guides are too tight. No big deal though.

azzie said:

I will second Mariah38 from GLR.

Give me dimensions of electronics and i will measure if it fits into Mariah AVbay & nosecone (it's hollow).

MD tend to fly high, I assume you also plan on tracking devices?

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Hi,

He mentioned an EggTimer TRS: https://www.eggtimerrocketry.com/page23.php

Tracking and deployment rolled into one with economy in mind. Kurt

For what it's worth:

If you are building a 38mm minimum diameter, THE way to go for avionics is a Raven in a Featherweight AV bay - super slick, ultra capable, takes up the least amount of room possible, integrated magnetic switch solves all kinds of switching problems and compromises, etc., etc. It's as close to perfect for the application as you can get.

Then, if you are using a GPS tracker, put that in the nosecone - perfect spot for such a thing. If you are radio-tracking, you can get away with attaching the tracker to your (apogee) shock cord, or put it in the nosecone.

Yes, that Raven and Bay are pricey items - but they are totally worth it.

my two pesos,
s6

stealth6 said:

For what it's worth:

If you are building a 38mm minimum diameter, THE way to go for avionics is a Raven in a Featherweight AV bay - super slick, ultra capable, takes up the least amount of room possible, integrated magnetic switch solves all kinds of switching problems and compromises, etc., etc. It's as close to perfect for the application as you can get.

my two pesos,
s6

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Raven is good, but requires a pc. Does not work with Apple. Someday I will get a pc for rocketry applications and I will definitely add a Raven to my altimeter collection.

Sort of true. The Raven does "require a PC" IF you want to change any of the parameters, or to review flight data beyond max altitude. But in most flight scenarios, there is no particular reason you would HAVE to do this. Straight out of the box, it works just fine for most normal flights. If you just want to fly your rocket, have an ejection event at apogee, another at 500' AGL, and know your max altitude, you do not NEED a PC.

Of course, having a PC gives you tons of options, allows you to fly more complex setups, and gives you incredible amounts of post-flight data - all very good things.

s6

stealth6 said:

Sort of true. The Raven does "require a PC" IF you want to change any of the parameters, or to review flight data beyond max altitude. But in most flight scenarios, there is no particular reason you would HAVE to do this. Straight out of the box, it works just fine for most normal flights. If you just want to fly your rocket, have an ejection event at apogee, another at 500' AGL, and know your max altitude, you do not NEED a PC.

Of course, having a PC gives you tons of options, allows you to fly more complex setups, and gives you incredible amounts of post-flight data - all very good things.

s6

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If that is all the flight data that is required, an RRC2+. might be the way to go. Cheap, small, and functional. Personally I really want velocity, especially in a minimum diameter rocket. One advantage of having Raven is good accelerometer based velocity. Anyway, all good stuff. Seems to be choices out there. Missileworks now has 38 mm nosecone with av bay for either RRC3 or RRC2+. Pros and cons to this, but adds some options for fliers.

ksaves2 said:

Hi,

He mentioned an EggTimer TRS: https://www.eggtimerrocketry.com/page23.php

Taking and deployment rolled into one with economy in mind. Kurt

Click to expand...

Kurt hit the nail.

He did say that he wants to try his hand at the Eggtimer TRS as he felt it was good value, mainly I think becasue I talked up the product and my satisfaction when dealing with Cris, however he may change his mind.

Anyone mention the Mariah from GLR? Or would that not fit the desired electronics?

Just_Keep_Flying said:

Anyone mention the Mariah from GLR? Or would that not fit the desired electronics?

Click to expand...

they waited until post #2 to mention it...

4kids49 said:

You should look at a Mariah 38 from Giant Leap Rocketry. I have built one, but have yet to fly it. The av bay is tight, but might work. There is some room in the nosecone. You might think about drogue less for the DD aspect. There is a fiberglass and non fiberglass version. I will check mine and the specs that you requested. You might also try a Blackhawk 38 from Wildman.

Click to expand...

DizWolf said:

they waited until post #2 to mention it...

Click to expand...

Guess that's what I get for skimming, huh? Long days at work and forum posting sure don't mix!

jhp;

mpitfield said:

Kurt hit the nail.

He did say that he wants to try his hand at the Eggtimer TRS as he felt it was good value, mainly I think becasue I talked up the product and my satisfaction when dealing with Cris, however he may change his mind.

Click to expand...

I don't know how one would fit a GPS tracker completely within a 38mm nosecone. I suspect the antenna would have to be facing aft into the main chute bay.
I'll take some pics of my project as I have the ebay bulkhead/ematch connectors and internal "screw ring" done. The "screw ring" is a .6" thick internal ring I'm going to epoxy in the coupler so the ematch wires can run through the center of the ring to the TRS. The .6" thick ring will allow for the screws to secure the aft end of the bay to have sure purchase of the coupler. Doing an elongated ebay with part of the shoulder/base of the LOC nosecone cut off. Will use a few small screws to secure the nosecone to the bodytube. I could epoxy it if desired. The plywood sled slides all the way forward and abutts against the nosecone base. In that way the forward mounted TRS has the antenna project forward into the nosecone. A 1200mah 20C 7.4V lipo will follow and the after coupler will be screwed into the bodytube. I will just have a screw switch on the pyro circuit and use a harness to the single battery. It should be able to handle ematches and the computer just fine. Use an Archtype cutter to unfurl the main. I would simply plug in the lipo to activate the TRS and bond to the receiver. Will be able to have it in standby mode. Slide the sled into the upper nosecone bay, secure the coupler with screws and finally turn on the pyro circuit through the static port. I'll do pictures when I get home from work. Cheap as I had all the parts on hand. Kurt

ksaves2 said:

I don't know how one would fit a GPS tracker completely within a 38mm nosecone. I suspect the antenna would have to be facing aft into the main chute bay.
Kurt

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Agreed. 38 mm nosecone is very tight. I can get a CSI tracker in if I remove unit from protective case and wrap in electrical tape. Then have to deal with 10 inch antenna. Also could have issues with baro altimeter getting accurate pressure readings in nosecone.

I've seen a few recommdations for the Mariah38 from GLR but their web site said that was a limited run and once they're gone, they're gone. I think they are all gone now!

Scratch? do whatever you want with it.

conman13 said:

Scratch? do whatever you want with it.

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Funny enough that is what he normally does, scratch builds but wanted to do a kit this time around.