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What is a pound worth? I thought about this in the past and came up with $30. Now, I realize it is much more complicated. I read an article that said a Boeing engineer, and a Cessna engineer both said that a pound out of a production airplane is worth north of $1000.
What is a pound worth to me? The next question should be, where is that pound? How much is a pound taken out of the tail worth, on a tail-heavy airplane? A lot. How much is a pound taken out of the propellor worth, on the same airplane? Maybe zero, or less than zero. I am never an advocate of adding ballast to an aircraft. Pouring lead into the balance section of the ailerons and elevators of the Bh will be the toughest part of the build for me. It kills me to add weight.
As builders, we are partners with the designers of the aircraft we build. We are building the idea of another, in this case Bob The 4 place BH is absolutely not CG challenged in any way, unless we are careless, or make choices that the designer did not intend.
The builder of a Pitts, or RV-3, will probably rightly choose to build the plane so that the solo CG falls within a narrow range that makes the aircraft a pleasure to fly. The Pitts crowd spends a huge amount of money to keep the nose light. The builder of a BH probably chose the airplane to haul people and stuff, either as a X-country airplane, or a bush/floatplane. Same thing for an RV-10, minus the Bush/float mission. If you build either airplane, so that the solo CG is in the middle or the range, you will be severely weight restricted by CG when you try to load it up. To maximize their utility, which I am defining as their ability to be loaded up with people/stuff, the empty CG needs to be as far forward as possible. At a minimum, as close to the forward CG as you can get with your choice of engine/prop. In my case, I am shooting for 1-2 inches forward of the forward CG limit. I won't be disappointed if it ends up 3". I am planning on carrying at least 75# of camping gear in the back of the baggage area on every flight to keep the CG within limits.
I won't be adding any weight other than an O-540. I will simply keep the back of the airplane as light as possible. There are not a lot of ways to do that. Keeping the baggage area floor and interior light, NOT adding extra weight in fabric and paint. The back of the airplane is mostly primary structure and flight controls.
The most efficient way to "add weight" to help the CG is the prop. I define efficient as the most effective way to move the CG forward per pound of weight added. I still can't advocate adding weight on purpose. But this thread, started by Battson about the CG effect of changing to a lighter prop, makes me think that changing to a lighter prop is not worth spending money on. If you want to change props to increase performance, go for it. If you want to change props because you broke the last one, or there is something wrong, obviously change the prop. I wouldn't use a heavy prop for its own sake either. I guess for me a pound of weight in the prop isn't worth much. I wouldn't spend money to remove weight from the prop.
I learned a lot. Thanks to all that contributed, or lurked.
What is a pound worth to me? The next question should be, where is that pound? How much is a pound taken out of the tail worth, on a tail-heavy airplane? A lot. How much is a pound taken out of the propellor worth, on the same airplane? Maybe zero, or less than zero. I am never an advocate of adding ballast to an aircraft. Pouring lead into the balance section of the ailerons and elevators of the Bh will be the toughest part of the build for me. It kills me to add weight.
As builders, we are partners with the designers of the aircraft we build. We are building the idea of another, in this case Bob The 4 place BH is absolutely not CG challenged in any way, unless we are careless, or make choices that the designer did not intend.
The builder of a Pitts, or RV-3, will probably rightly choose to build the plane so that the solo CG falls within a narrow range that makes the aircraft a pleasure to fly. The Pitts crowd spends a huge amount of money to keep the nose light. The builder of a BH probably chose the airplane to haul people and stuff, either as a X-country airplane, or a bush/floatplane. Same thing for an RV-10, minus the Bush/float mission. If you build either airplane, so that the solo CG is in the middle or the range, you will be severely weight restricted by CG when you try to load it up. To maximize their utility, which I am defining as their ability to be loaded up with people/stuff, the empty CG needs to be as far forward as possible. At a minimum, as close to the forward CG as you can get with your choice of engine/prop. In my case, I am shooting for 1-2 inches forward of the forward CG limit. I won't be disappointed if it ends up 3". I am planning on carrying at least 75# of camping gear in the back of the baggage area on every flight to keep the CG within limits.
I won't be adding any weight other than an O-540. I will simply keep the back of the airplane as light as possible. There are not a lot of ways to do that. Keeping the baggage area floor and interior light, NOT adding extra weight in fabric and paint. The back of the airplane is mostly primary structure and flight controls.
The most efficient way to "add weight" to help the CG is the prop. I define efficient as the most effective way to move the CG forward per pound of weight added. I still can't advocate adding weight on purpose. But this thread, started by Battson about the CG effect of changing to a lighter prop, makes me think that changing to a lighter prop is not worth spending money on. If you want to change props to increase performance, go for it. If you want to change props because you broke the last one, or there is something wrong, obviously change the prop. I wouldn't use a heavy prop for its own sake either. I guess for me a pound of weight in the prop isn't worth much. I wouldn't spend money to remove weight from the prop.
I learned a lot. Thanks to all that contributed, or lurked.
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