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Date: Wed, 17 Mar 2010 10:39:46 -0400
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] weighty subject
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Bktrub@aol.com wrote:
> Today was the day of judgement, the measure of my building prowness- 
> no, not the first flight, but the weight and balance. My plane weighs 
> 1091 lbs, weighed as it should be- no usable fuel, full oil and 
> coolant. I for one would go with the aluminum housings if they cost me 
> up to  $1500 more than the cast iron ones. If they saved 70 lbs total, 
> that would be around $21 for each pound saved, to get my plane down to 
> a more svelte 1021 lbs. I'm sure I could probably get another 15 lbs 
> off if I did some weight reduction on my Shertz beam front mount, 
> along with other things. I also went a bit heavy on my engine mount- 
> 1" dia x .049 thick tubes on some of the mount. I at least have 
> confidence that my mount should hold up. The CGs all work out OK- 
> design range is between 68.7 -77.7 inches aft of datum. Here is how it 
> works out:
>  
>
>
Is that an engine mount or a bridge you have there?

Taking 70lbs off the engine will only be helpful if you can take 70lbs 
off the tail someplace, if you want to keep the CG where it's at.  Of 
course, if you could get both sides down, you would be where Vans says 
most RV-4s are.