Tuesday, November 17, 2015

CP, CG and Thrust/Weight, oh my

I have made no building process but I did put in a 'chute and did another quick look at weight and CG issues.

The weight as it stands is 23oz w/o motors. This is three ounces over my rough guess and will still grow a bit. With a 'full load' (i.e. including rear mounted D12's), I am still clearly doing fine. Since I'm not sure about using the rear mounts, I took a look at the thrust/weight for just three D's and eight C's. Those will add about 11 oz and are the equivalent of a 121G65. At 34oz, I should also be fine. I think even with the few missing components it should be OK. The wildcard is whether I need a lot of nose weight.

Unloaded, the CG is about an inch behind the leading edge of the main wings. I don't have enough spent 18mm motors but suspect, if I look both at the completely empty and fully loaded cases, I should be OK. I will have to swing this bad boy at some point but think the current position may not be too far off. Most winged rockets that I have built require the CG hovering around the leading edge of the main wings, mas-o-menos. Of course, this ain't your daddy's winged rocket.

The main problem may be those rear mounted D12's. They are a long way from the current CG and further than the tip of the nose cone. For now I'll keep building and will look back at the 'full load' values.