Giant Leap Rocketrys new Mariah 38 kit review

I'm looking forward to seeing the build on this, Jim!

-Kevin

blackjack2564 said:

Well it came today. Read the manual several times.

Dry fitted the parts for kicks. Didn't realize the fins get glassed on, but it comes with the needed 6oz.

The B box is 4.25 in. No way my Missile mini & 9v would fit. .75 short.

After a bit of fooling around, I figured out how to make it work.
Just needed to get parts in hand to play with. Nice job on the instructions, but you definitely want to read them a couple times before you start.

Will start a build thread after I do some more studying.

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It's been over 2 hours already! What are you waiting for?:bangpan:

JAL3 said:

It's been over 2 hours already! What are you waiting for?:bangpan:

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He is a slow reader...:duck::lol:

Pantherjon said:

He is a slow reader...:duck::lol:

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I thought he would just look at the pictures.

Reading...what kind of wildman, excuse me, mildman is that ?

JAL3 said:

I thought he would just look at the pictures.

Reading...what kind of wildman, excuse me, mildman is that ?

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Tsk Tsk Tsk Jim.....:no:

Mike

JAL3 said:

I thought he would just look at the pictures.

Reading...what kind of wildman, excuse me, mildman is that ?

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:surprised::surprised::surprised::surprised:

You'd better find a rock to hide under...

Well, I just talked to Jim this evening and he DOES have a legitimate excuse in that he has a horrendous cold at the moment..A cold so bad that today our high tempurature was almost 70 and he was bundled up with the heater on and was still cold..Give him a couple days and he will be back up to full speed!

Have you started yet Jim? Should I buy one?

Mike

go ahead and buy one its a great kit i just wish i had a camera so that i could post pictures of mine, my favorite part about glr kits is that for most of them(including the mariah 38) all you have to supply is epoxy, paint, an altimeter, motor and possibly a motor retainer, its 80 bucks for the kit and believe me this kit will take all the abuse that you can throw at it with a 38mm motor built by the instructions this spring or summer mine is gonna go up on a loki j1000, but believe me buy the kit because whats the worst that can happen? its rocketry if your not learning something new or lookin for a better way to build that mousetrap then your not fully in the hobby

cmcain said:

go ahead and buy one its a great kit i just wish i had a camera so that i could post pictures of mine, my favorite part about glr kits is that for most of them(including the mariah 38) all you have to supply is epoxy, paint, an altimeter, motor and possibly a motor retainer, its 80 bucks for the kit and believe me this kit will take all the abuse that you can throw at it with a 38mm motor built by the instructions this spring or summer mine is gonna go up on a loki j1000, but believe me buy the kit because whats the worst that can happen? its rocketry if your not learning something new or lookin for a better way to build that mousetrap then your not fully in the hobby

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AMEN!!

Well Put!

Over a month since the release, and still no pictures. :confused2:

Rocketman248 said:

Over a month since the release, and still no pictures. :confused2:

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I was struck by a full sized Chevy truck walking through the parking lot @ my work!
Driver was doing Aprox. 18-20 MPH!
Darn near broke my back!
Rocket building has stopped for the moment.
Until I can get moving around better.
Undergoing physical therapy, pain pills & numerous other treatments!

I would like to see your pictures. So I can give tips, help etc.

Thanks

I am almost done building it. I took some pictures and will post them next week. I hope to have it ready for the launch this weekend. It will be naked, ut it might fly.

I will be seeing 'Crazy' Jim Hendricksen NEXT weekend and will try to remember to take my camera to get some pictures..Looking forward to seeing your pics Chuck, have fun at the launch this weekend, tell the guys hi! (I won't be there- bloody job!)

has anybody built and flown their mariah 38 yet? if so what altitudes are people getting and what seems to be the motor of choice so far?

The Mariah instructions tell me to epoxy the nosecone to the short airframe and the breadbox Av-bay but if I do that I can’t load my nosecone with a GPS or tracker. Am I missing something here or should it be ok to friction fit the nosecone ?

nzxela said:

The Mariah instructions tell me to epoxy the nosecone to the short airframe and the breadbox Av-bay but if I do that I can’t load my nosecone with a GPS or tracker. Am I missing something here or should it be ok to friction fit the nosecone ?

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What about using PML's pop-rivets or some small plastic screws to hold the N/C on? That way you could take the N/C on and off.

i epoxied my nosecone on and made a small bracket to hold my altimeter against the forward bulkhead of the breadbox and then ran the antenna up into the nosecone thats how they did it on the prototype and it worked great. as for the rivets from pml yes you can use them but you have to be careful with the spacing because of the static port for the avbay and itll add drag to the model which is the main reason they have you epoxy it on. i know kent is kicking around a few ideas to get around this issue but to my knowledge he hasnt found a good solution yet. ultimately epoxy, friction fitting or rivets will work its mainly personal preferance and what your comfortable with, personally i hate fricion fitting so i modified mine to use 1/16" styrene rod for shearpins to hold the avbay and booster together

Put a piece of all-thread in the nose, and run it through the bulkhead. Then, to attach it, drop on a washer, and spin on a wingnut. I'm betting that nosecone is pretty light, and a piece of 4-40 allthread would be sufficient.

If you don't like weight, you could use aluminum allthread.

-Kevin

Guys,

I am trying to think of a way to make the nose cone removable without shear pins. I thought of a screw on method, but that may add too much cost. Maybe an estes type plastic retainer?

Chuck

cwbullet said:

I am trying to think of a way to make the nose cone removable without shear pins. I thought of a screw on method, but that may add too much cost. Maybe an estes type plastic retainer?

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All-thread will cost you a few dollars.

A plastic twist-lock retainer is going to be hard to adhere sufficiently that it doesn't break loose on installation/removal.

-Kevin

troj said:

All-thread will cost you a few dollars.

A plastic twist-lock retainer is going to be hard to adhere sufficiently that it doesn't break loose on installation/removal.

-Kevin

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I think all thread is counter-Mariah thinking,, just a lot of unessesary weight...

why does the nose cone need to be removable... ?

You may try fixing it with a tad bit of CA ?? usualy can break it loose.

But i would just friction fit it...

ClayD said:

I think all thread is counter-Mariah thinking,, just a lot of unessesary weight...

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Aluminum allthread doesn't weigh much.

why does the nose cone need to be removable... ?

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Because he wants to put a tracker in it.

You may try fixing it with a tad bit of CA ?? usualy can break it loose.

But i would just friction fit it...

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No way I'd friction fit with a tracker in there.

-Kevin

troj said:

Aluminum allthread doesn't weigh much.



Because he wants to put a tracker in it.



No way I'd friction fit with a tracker in there.

-Kevin

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4-40 alumninum has no strength in tension... if your going to do that, put a captive nut on the inside of the shoulder and a small 4-40 counter sunk screw in the side. Place the load in shear...

I would trust friction fitting a 38mm nose cone way before 4-40 aluminim in tension.

ClayD said:

4-40 alumninum has no strength in tension... if your going to do that, put a captive nut on the inside of the shoulder and a small 4-40 counter sunk screw in the side. Place the load in shear...

I would trust friction fitting a 38mm nose cone way before 4-40 aluminim in tension.

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Since aluminum is ductile, it will pretty much always fail in shear rather than in tension. This means that if you place an aluminum rod in tension, the failure surface will be at a 45 degree angle to the load, and it will therefore have 1.414 times the area of the rod (1/sin(45)), and it will carry 0.707 times the shear load (for a given total force). In other words, it will take twice as much force to break a given aluminum rod in tension (1.414/0.707) as it will in shear.

In other words, definitely trust 4-40 Al in tension more than in shear. It'll carry twice the load (this is an approximation, admittedly, but it's fairly close to accurate).

ClayD said:

I think all thread is counter-Mariah thinking,, just a lot of unessesary weight...

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I wouldn't be terribly surprised if a bone stock mariah, built as light as possible, was substantially below the optimum mass for a lot of the larger 38mm motors, and the extra weight would actually help it go higher.

How dose one calculate optimum weight ?

cjl said:

Since aluminum is ductile, it will pretty much always fail in shear rather than in tension. This means that if you place an aluminum rod in tension, the failure surface will be at a 45 degree angle to the load, and it will therefore have 1.414 times the area of the rod (1/sin(45)), and it will carry 0.707 times the shear load (for a given total force). In other words, it will take twice as much force to break a given aluminum rod in tension (1.414/0.707) as it will in shear.

In other words, definitely trust 4-40 Al in tension more than in shear. It'll carry twice the load (this is an approximation, admittedly, but it's fairly close to accurate).

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all-thread is not a rod. it has compression points. its failure in tension is at the compression point . It will almost always be in line with the thread cut and certainly not at 45degrees.

In tension, the shear load is drasticly reduced.... so to tighten an allthread, and then place some form of shear, (tightening a nut, and then loosening it.. over and over) fatiges the all thread...any other shear load, landing on the nose cone.. could also cause a failure.

any anomolies in the alloy cause hard spots and softspots, all of this can be the week point.

I could snap the head of a bolt far easier than shearing one....

KPM61 said:

How dose one calculate optimum weight ?

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The only method I know is brute force, and I think this is the method RockSim uses.

Adjust weight up or down by a bit, and see how your altitude changes. That tells you the direction you need to move, then move in gross steps in that direction, rerunning the sim, until you get the max altitude dropping again. Now you have it bracketed. Keep doing smaller steps in between, until you get a final number.

-Kevin

They need a HP version of Rocksim. This Engine ejection thing kills me, as I just want to pull my hair out trying to workaround it!
At least make it so that you can turn off any motor ejection timing for staged rockets without having to pay $1000+ for the commercial version.


JD