Mac Performance Median 54mm (29mmt) Build

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liv3mind

Amateur Hour
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So I actually still have my Mac Performance Black Fly build going that I am getting ready to do prep and paint work to finish off then fly for my L1 cert in (hopefully) October. I figure I have some time for a couple new projects, this is one of them, I will post the others as I have time to.

Before I decided to build the Black Fly, I had played around with the idea of designing my own rocket that could fill the gap between building the Estes kits and working with larger kits made of different materials. I wanted it to be very stable, and fairly simple. Strong. 3 fins and a nose cone made of canvas fit the bill. I wanted it to sit in the 29mm range because there is a wide range of motors and altitudes that can be had. I wanted it to be a fairly easy and straightforward build that could be certed on if desired. The closest launch to me has a waiver height of 1k most of the time, so that was a consideration; this baby will well under 900ft and well over 4k. I also wanted to make it capable of flying mach if given the chance; it most certainly is. After playing around with OR for the last couple months, I finally had a design I was happy with. By that time I had already received and mostly built my Black Fly, and since I have become a loyal Mac customer (Mike is the BEST!) I reached out to him for his input, and finally to have him get the parts together for me. He has been an invaluable source with this project. He is sending me a large order, which this is only a part of, so I expect it will be here next week sometime. For me I will be flying CTI since that is what is easily available with my local club. So any reference to motors will be toward that unless otherwise mentioned.

Either way I couldn't hold off my excitement till I receive it, so i figured I would start my thread and cure the itch a little.

To start this off here is the OR file for it and a shot of it :)

I present The Median

FONRgXQ.png


View attachment Median.ork
 
Very nice! I normally don’t like tail cones all that much but it looks really good on there! What size body tube is that?
 
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And it's here! I will try to get some better quality shots either today or tomorrow but here are a couple IMG_20180519_084654.jpegIMG_20180519_085012.jpeg
 
All this internal fillet stuff seems to be more about recovery than flight, right? Guys are flying 29mm tubes with surface mount fins well above mach.
 
All this internal fillet stuff seems to be more about recovery than flight, right? Guys are flying 29mm tubes with surface mount fins well above mach.

It’s probably overkill, but this one does sim as Mach capable. For me it’s more about practicing for other builds, but since it’s open, when in Rome and all that.
 
Nice design, very clean & simple.

Out of curiosity how did you do your internal fillets and what epoxy did you use for them ?

Mikes instructions to me were:
"There is no need for tip to tip. I triple dip the root of the fin. Coat it drop it in. Pull it back out and coat the root again put it back in. I do that 3 times. It does make an awesome fillet between the fin and motor tube. I'm lazy so I just do outer air-frame fillets and them foam the booster. I fly my stuff well over Mach all the time done this way."

If things go to plan, we (PyroShark & I) will start our build (MAC 3" Scorpion XL) this weekend - but starting from the opposite end. Need to see if it's possible to fit the avionics bay to the nose cone and still access the screw on the top of the Wildman or do we have to wrap the nosecone before assembling it. Fun times ahead...
 
Nice design, very clean & simple.

Out of curiosity how did you do your internal fillets and what epoxy did you use for them ?

Mikes instructions to me were:
"There is no need for tip to tip. I triple dip the root of the fin. Coat it drop it in. Pull it back out and coat the root again put it back in. I do that 3 times. It does make an awesome fillet between the fin and motor tube. I'm lazy so I just do outer air-frame fillets and them foam the booster. I fly my stuff well over Mach all the time done this way."

If things go to plan, we (PyroShark & I) will start our build (MAC 3" Scorpion XL) this weekend - but starting from the opposite end. Need to see if it's possible to fit the avionics bay to the nose cone and still access the screw on the top of the Wildman or do we have to wrap the nosecone before assembling it. Fun times ahead...

BSI 15min epoxy. I used a technique I picked up from the black fly master, a wooden dowel with some epoxy on it in a straight line, insert in air frame, press to desired fillet area rotate and pull out. It leaves a pretty minimal amount of extra inside. It’s definitely not necessary for me to do internal and external fillets on this, more for practice.

Thank you, yeah I was really going for simple and effective when I set out to design it. Capable of under 1k flights was mandatory for me as our closest field has a fairly low waiver. But it has a very broad range.

The scorpion was on my list I will be stoked to see it built, doing a thread? I have a 3” black fly that’s done (aside from paint) and a zodiac, hyper 54 and 4” Big Bertha spin-off that I need to build, and my wife has an MPR she is working on. I might have just placed a unique custom order with mike that’s being delivered Thursday too ;) one of these days we will go out and cert haha but building MAC stuff is addicting.
 
First coat of primer down, I plan to do a good bit of sanding and atleast 1 more coat of primer with sanding before color.

IMG_0635.jpg
 
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And paint is on. Retainer got JB treatment. Decals tomorrow. Better pics tomorrow. Don’t mind the LOC iris, some internals are drying on that.

IMG_0641.jpg
 
Does anyone have any input as to single use 29mm motors having enough ejection charge to fly this safely at a smaller field? Under 1k?
 
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Based on other rockets that fly on 29mm AT SU motors, probably.
Look up the ejection charge weight of AT single use motors and use an ejection calculator

Is your loaded (w/ motor) rocket less than 1500 grams?
 
Based on other rockets that fly on 29mm AT SU motors, probably.
Look up the ejection charge weight of AT single use motors and use an ejection calculator

Is your loaded (w/ motor) rocket less than 1500 grams?

Rocket loaded (sans motor) is 836.3109g and the motor weighs roughly 80g (sorry I do not have one on hand yet).
 
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