# Estes Altitrak???????

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#### El Cheapo

##### Well-Known Member
Has anyone ever used one? I have one in the bag that I won in a raffle and am curious if it's even worth the effort to cut the bag open.

#### Peartree

##### Cyborg Rocketeer
Staff member
Global Mod
I have one and (almost) never use it. Either we don't have enough people, don't have enough time, or simply don't care. I have it in my range box "just in case" but then you need a calculator to go with it.

#### CharlaineC

##### Well-Known Member
I have two altitracks and love them keep them in the range box and use them to when i have a few people extra. or with the scouts

#### cjl

##### Well-Known Member
this topic begs the question - do Estes rockets actually reach the altitude maximum listed on the kit package? I think what we are discovering is that they don't because we have flown a Blue Ninja on a D12-5 about eight times in a year, at least, and got 250-270 feet at 60 deg. F dry air. The 2007 catalog says max altitude for the Blue Ninja is 700ft. and lists C11-3 and D12-3 as the only engine options.
Honestly, you should be getting quite a bit higher than that. It may not hit 700, but a D12 is enough power to get a blue ninja sized rocket to at least 500, despite the plastic fin can.

#### Micromeister

##### Micro Craftman/ClusterNut
TRF Supporter
I have two altitracks and love them keep them in the range box and use them to when i have a few people extra. or with the scouts

We've done the same thing using 3 station tracking using 3 of the much older altiscopes back in the 80's. Once the Scouts learned how to hold them consistantly they were closing tracks within 7points. They are fun little gidgets for sport flying with a group, particularly if your group doesn't have a set of theodolites.

#### Queeg500

##### Well-Known Member
Honestly, you should be getting quite a bit higher than that. It may not hit 700, but a D12 is enough power to get a blue ninja sized rocket to at least 500, despite the plastic fin can.
ok, we are using the small field calculation: base = 250 ft, times tangent = altitude, then divide the altitude by 2. With this last Ninja flight the angle was 65 deg. --> 2.14 tangent times 250ft. = 535ft. Dividing this by 2 is 267.5 feet.

#### cjl

##### Well-Known Member
ok, we are using the small field calculation: base = 250 ft, times tangent = altitude, then divide the altitude by 2. With this last Ninja flight the angle was 65 deg. --> 2.14 tangent times 250ft. = 535ft. Dividing this by 2 is 267.5 feet.
Why are you dividing by 2? Not only do I not see any need to mathematically, 535 feet is in the range of reasonable altitude for that rocket on that motor.

#### Queeg500

##### Well-Known Member
I'm dividing by two because the instructions on the back of the package say to do exactly that: "Note: For low altitude rockets, pace off 250ft. and divide hight by 2. For high altitude rockets, pace off 1,000 ft. and multiply height by 2".

#### cjl

##### Well-Known Member
If you're calculating directly based on the angle, there is no need to divide by two. If you are using the height values read directly off of the device, you would have to divide by two because they are precalculated assuming a 500 foot baseline.

#### Queeg500

##### Well-Known Member
Thanks CJL. I took the instructions to mean halve the height from the trig caluclation not the Altitrack meters reading.

#### cjl

##### Well-Known Member
That definitely explains the odd altitude readings

#### bobkrech

##### Well-Known Member
What the instructions are trying to do is to make the angle about 45 degrees to minimize the effect of elevation angle measurement errors. If you are off by +/- 1 degree in your elevation angle measurement at 45 degrees, your calculated altitude will be in error by only 3.5%, and within 4% for elevation angles between 30 degrees and 60%, and within 5% from angles of 22 degrees to 68%. See the attached plot.

If your flying to 250', then the base is ideally 250'. If your flying to 500', then the base is ideally 500'. If your flying to 1000', then the base is ideally 1000'. Etc.

The altitude for an 65 degree elevation angle with a 250' baseline is 250' x tangent (65) = 250' x 2.1445 = 536' +/- 4.56% = 536 ' +/- 24.4' error for each degree of elevation angle error.

With a 500' baseline and the same altitude the angle becomes arctan(536/500) = 47 degrees and the measurement error would be reduced to 3.5% or +/-18.4' per degree of elevation error. For fun flying it not that important, but for competition it is.

Bob