alt calculaitions

ok im looking at starting out and I got some good advise but now im looking at some rockets and I need some calculations on how high the rocket will go so I stay in the waver we get at that field the rocket im looking at is on loc precision and it is the magnum 3 with the payload. specs are 90" long 5.540" diameter and empty weight is 136 ounces. said it take a J motor to get to 1800 feet but a calculator I found is saying the H123W-14A im looking at will push it to almost 5000 feet if anyone can do a calculation real fast and let me know please. and I know there will be more weight with atls and battery and all that but if it stays in raw it will stay in complete

Have you tried thrust curve?
https://www.thrustcurve.org

I just did a quick sim in WRASP32 with an AT H123W and it says it's too heavy for that motor. The sim is only to 408 ft. The same 136 oz. 5.540" diam 0.7 Cd rocket on an AT J350W shows 1790 ft.

What ever calculator you were using, I think something is wrong.

thanks handeman unforchunantly I cant run a J this rocket is going to be a cert 1, 2, and 3 rocket for me

the most I can stuff in for cert 1 is an I165

ok running the cal I found its saying 1800 feet on the I

If you are doing your L1 on a Loc Magnum, it is a big rocket. An H motor is flat out in my opinion. It will be heavier by the time you put it together due to parachutes, harnesses, epoxy, and paint. I would say for the L1 you need a close to maximum I motor. From Aerotech I would look at the I366 or I435. From CTI maybe an I 470 or I 540 White Thunder. You need a little altitude to give you deployment time to inflate...

Simply too much rocket for an H

You really need to know total weight when the rocket is completed to determine which motors will work or not work. I would say forget about that I 165 even at 137 oz. Your thrust to weight ratio is not at the minimum it should be. As mentioned one of those I's with a higher impulse would work.

markkoelsch said:

If you are doing your L1 on a Loc Magnum, it is a big rocket. An H motor is flat out in my opinion. It will be heavier by the time you put it together due to parachutes, harnesses, epoxy, and paint. I would say for the L1 you need a close to maximum I motor. From Aerotech I would look at the I366 or I435. From CTI maybe an I 470 or I 540 White Thunder. You need a little altitude to give you deployment time to inflate...

Simply too much rocket for an H

Click to expand...

I just looked at your opinun there good but do you know of any that can be in a 54mm don't get me wrong I don't mined running the adaptor to go to 38 but I don't want to relly chance a double adaptor do to the motor mount being a 75mm and all im finding are going to 54mm then id have to do another to get to 38mm

I did find this motor CTI I445 its got the 500n thrust but its under the 500 total but on the good side only 1 adaptor needed since it is a 54mm also found a motor only 300 n thrust but 600 in the total with a 6 s burn time its a 2 grain instead of the I445's 1 grain

For an I motor, I would suggest the AT I600R in the 38/720 case. It has almost 175 lbs of initial thrust so the 5:1 minimum ratio shouldn't be an issue. Then you could put a J350W or J420R in it and use the same case for L2.

I don't know what type retainer you are using, but LOC has a 38 to 75 adapter https://shop.locprecision.com/product.sc?productId=85&categoryId=25

At 54 mm is a little slim for this rocket in L1. Cti is a little slim too in 54mm l1, but a i445 might get you 900 feet or so.

I really think the 38mm are a much better option for I motors.

For the L2 there is a plethora or of choices. Personally, from AT I would look at the J800 or the K805. Cti 54 mm j760 seems good, as would a number of K motors.

I would build it, and weigh it with everything on board. A final weight is needed, but I hope the above helps.

I am also building a Magnum with payload for my L2 on a J400, then K535 and nearly complete. Once I get home ill try and post a final weight with harnesses and post them on here with specifics

I would fly it in the "short" mode for L-1. Just put NC on fin can, leave off the coupler/payload.
Should save some weight.

Jim's got it--right there: ditch the extension. Save you on weight, and open up motor choices in the smaller end.


Later!

--Coop

That is certainly an option. I only recommended what I did as he was talking dual deploy.