L3 build - 8 inch Madcow Pike

pyrobob said:

Dang! That 75mm hardware looks like a 54 or even 38 compared to that rocket!

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It is strange to see the big 75mm/6400 hardware and think that if I keep the rocket on a diet it might be enough for a first flight. I am fairly sure it will need more power.

Okay, Tim Taylor. :wink:

robertv2 said:

It is strange to see the big 75mm/6400 hardware and think that if I keep the rocket on a diet it might be enough for a first flight. I am fairly sure it will need more power.

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Why? a Loki 76/6000 M2550 Blue has 3000 Ns initial thrust and stays above the 2550 average for the first 1.8 seconds or so of the burn. At 5:1 ratio you should be good for up to 130 lb rocket.

Is there a minimum speed or altitude you're looking for?

Handeman said:

Why? a Loki 76/6000 M2550 Blue has 3000 Ns initial thrust and stays above the 2550 average for the first 1.8 seconds or so of the burn. At 5:1 ratio you should be good for up to 130 lb rocket.

Is there a minimum speed or altitude you're looking for?

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I haven't looked at Loki. I will have an accurate weight soon, for now I am estimating 85 lbs all up . My goal for the first flight is about 5:1 thrust to weight and about 4000 ft. altitude

I have given it a lot of thought and decided not foam fill the fin can. That is nearly one cubic foot of space and as I think about it because of the fin pockets the foam will not touch anything that could possibly move anyway. Another weight saving change is instead of using Pro-line 4500 for the fillets I made small fillets with Aeropoxy and I will go back with Aeropoxy light so it is lighter and easier to sand.

robertv2 said:

I haven't looked at Loki. I will have an accurate weight soon, for now I am estimating 85 lbs all up . My goal for the first flight is about 5:1 thrust to weight and about 4000 ft. altitude

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OK, you can get the 5:1 thrust with 75mm motors, but getting 4,000 ft with a 85 lb rocket, that's another issue. Sounds like a 98 is what you need for that.

Good luck! :headbang:

I have a " best guess " of weight and CG that I keep refining in my mind and I looking at sims for a range of weights, but I am only a week or two more of airframe construction away from a final answer. On two past builds I have had to reorder motors and parachutes that I bought before I started and at this pay grade you need to right the first time. When I post pictures this week-end they are not fittings, the bottom end is finished and after some hole drilling I will be on the av-bay.

I am close to a final weight on the Pike, complete except for a sled in the av-bay it weighs 65 lbs. The 40 inch FW nose with coupler, bulkheads and tracker bay is 12.6 lbs of the total. If the rain ever stops I will post some pictures next to the house and truck for scale. I have a lot of holes to drill and I am waiting on a pair jaw stands I ordered to start on them, then on to electronics.

It rained every time I had a few minutes so I didn't get pictures, I will soon. I did get a Fruity Chute 144 " Ultra-Iris chute and deployment bag ordered. I also ordered Y harnesses for all the twin eye-bolt connection points. I have a custom 36" sky angle drogue and a pair of One bad hawk shock cords, the only recovery gear I am missing is a pilot chute. I use a 30" TFR Crossfire as a pilot and I am planning on a 48" Crossfire on this beast.

Robert Watson aka Pyrobob at buyrocketmotors.com came thru with a good price on a 75mm/7680 case, I will order a M1850 reload when it gets a little closer to Balls24.

Looking forward to the pics.

If this new found sunshine holds out till I get off I will post some pictures today. This has been a crazy couple of weeks in north Texas
.

Bat-mite said:

Looking forward to the pics.

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robertv2 said:

If this new found sunshine holds out till I get off I will post some pictures today. This has been a crazy couple of weeks in north Texas
.

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Yeah, been praying for you guys. Pretty awful.

Wow, the Pike looks great!

Fillets get sanded on Friday and I have holes to drill. When the chutes get here I want to ground test before I make it too pretty. Then it is on to the av-bay.

I can't even imagine having a rocket that big!

Okay, that came off really weird....

Awesome job.

Looking great so far! Can't wait to see it completed and flying.

Thanks, I appreciate that. I got the fillets sanded and holes drilled and tapped for four #4 screws as shear pins at both ends. More pictures soon.

isobig said:

Looking great so far! Can't wait to see it completed and flying.

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This is my 5.5 Pike, would I be in a rut to paint the 8 inch Pike the same color ?

robertv2 said:

This is my 5.5 Pike, would I be in a rut to paint the 8 inch Pike the same color ?

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Not at all, I have several rockets painted with the same color scheme.

If ya like it....use it over & over again!

I think its a great color. Why not the same.

Paint it black with white lettering and maybe add a silver tip ?

I avoid black paint. This is Texas and one day the sky will clear and the waters recede, then the sun will roast us again.

AfterBurners said:

Paint it black with white lettering and maybe add a silver tip ?

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robertv2 said:

I avoid black paint. This is Texas and one day the sky will clear and the waters recede, then the sun will roast us again.

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Then how about a camo paint scheme ... flat colors easy to paint and very forgiving

Full disclosure - The 5.5 Pike was the second rocket I painted that color, this is Almost too Pretty to Fly a 4"Frenzy.

How about chartreuse? Or heliotrope?

:grin:

Candy Apple Red !

This is the av-bay from the 5.5 Pike, I am going to adapt it to the 8 inch and use it for the cert flight. I have 5 successful flights just the way it is and 6 more with an earlier version using these two in a 4 inch frenzy. I trust it and would not have a way to test fly a new 8 inch setup. Last picture is hole pattern for lids to finish tonight.

fillets about 90 % done I will finish when prepping for paint. shear pins and other holes drilled.