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  #1  
Old 11-25-2013, 09:55 AM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
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Default Admitting to a Weight Problem...

My name is Michael and I have a weight problem...

...actually, my airplane does. According to the W&B info in my new Rocket it weighs 1229 empty. Considering the modest panel, I figured this was a little on the heavy side, but I know where to trim some fat. Imagine my disappointment when I did my own weight on it last night and found out it was in fact 22 pounds heavier - a fairly portly 1251!

I use a very nice set of digital race car pad scales that I have found to be highly accurate, and in fact rolled the airplane on and off the scales a total of 6 times, swapping load cells each time. I did a series of 3 in the three point attitude to establish basic weight, then 3 more with the airplane leveled. All 6 "totals" were within 2 pounds, so I'm pretty confident that this is reality. Not sure how my airplane gained more than 20 pounds in only 58 flight hours, but it is what it is.

So I guess its time for a diet program. First order of business is to replace most of that heavy, fire sleeved hose found under the cowl with stainless hard line. If my experience with the -8 is an indication, I should be able to drop 6-7 pounds right there. There also seems to be a lot of extra structure in the current avionics installation, so I should be able to shed a few more there, and the heater ducting and controls is a few more. In any case, I think I'm 50 pounds north of where I'd like to be, so we'll see how close I can get.

I think the lesson for builders is that this stuff adds up fast. It's much easier to build light in the first place than to remove it after the fact.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C

Last edited by Toobuilder : 11-25-2013 at 02:07 PM.
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  #2  
Old 11-25-2013, 10:07 AM
sailvi767 sailvi767 is offline
 
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Location: Charlotte NC
Posts: 1,388
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I recently weighed our RV and found it came in about 40lbs more then I expected from the original WB. I think you will find everyone wants the lightest aircraft they can get at the initial weigh in so they tend to try and mitigate anything that would save weight. Often they are weighed before paint, some interior items, handheld GPS's or radios are not in the aircraft and fluids kept to a minimum. I don't think your weight increase is at all unusual.

George
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  #3  
Old 11-25-2013, 10:18 AM
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Toobuilder Toobuilder is offline
 
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I hadn't considered the possibility it was weighed before paint George, but you're probably spot on. All paint is heavy, and there is a bunch of it on this particular airplane. In fact, one of the red flags with this airplane was the fact that all the rivet heads are filled. Yes, I bought the airplane anyway, but I think the true measure of craftsmanship of a metal airplane is being able to see every rivet, set to perfection, under minimal paint.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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  #4  
Old 11-25-2013, 11:32 AM
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Low & Slow Low & Slow is offline
 
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Default Shed weight instantly

1251 - 1229 = 22. Presto! You just lost 10 lbs.
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  #5  
Old 11-25-2013, 11:47 AM
Tom Martin Tom Martin is offline
 
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Location: Ontario, Canada
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Michael
My first HRII came in at 1169 without paint. This was quite light but it had no interior, and a very basic panel. Weights have gone up since then. My EVO has a much heavier wing and with a IFR panel comes in at 1292. Many rockets are in the 1300 lb area. Interiors, panels and redundant systems really add weight. Mark has, had?, some really nice carbon fibre wheel pants that could save you quite a bit of weight.
The aircraft seems to handle the weight ok but my first light rocket was a real cream puff. Next to my EVO it is my second most favorite plane.
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Tom Martin RV1 pilot 4.6hours!
CPL & IFR rated
EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger

Fairlea Field
St.Thomas, Ontario Canada, CYQS
fairleafield@gmail.com
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  #6  
Old 11-25-2013, 02:06 PM
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Toobuilder Toobuilder is offline
 
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Quote:
Originally Posted by Low & Slow View Post
1251 - 1229 = 22. Presto! You just lost 10 lbs.
Darn that basic math!

...and I feel a little better. Thanks
__________________
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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  #7  
Old 11-25-2013, 02:51 PM
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Ironflight Ironflight is offline
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And don't forget....take 20 lbs off the pilot, the airplane performs better and the pilot keeps his medical longer!
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Paul F. Dye
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RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
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  #8  
Old 11-25-2013, 07:08 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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Default warning: thread drift

Someone mentioned weight gain from filled rivets. I'm curious; has anyone tried to quantify how much weight would be gained from 'filling' rivets? I'm not talking about a layer of bondo over the entire skin; I'm talking about doing a proper job of dimpling & riveting, followed by filling the tiny groove between the edge of the rivet head & the edge of the dimple. I'd bet that there would be less weight gain there than what goes on a typical cowling.

One technique I've read about is to use a finger to wipe thinned proseal across each rivet head. Using that technique, I'd bet that the weight difference wouldn't even show up on typical scales.

Any other opinions? :-)

Charlie
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  #9  
Old 11-25-2013, 07:33 PM
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Toobuilder Toobuilder is offline
 
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I think there's a difference between carefully filling each rivet vs loading on the paint until the rivets disappear. Not sure which one mine is, but I have an idea.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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  #10  
Old 11-25-2013, 07:40 PM
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GalinHdz GalinHdz is offline
 
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Quote:
Originally Posted by Ironflight View Post
And don't forget....take 20 lbs off the pilot, the airplane performs better and the pilot keeps his medical longer!
Man ain't that the truth.

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