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Admitting to a Weight Problem...

Toobuilder

Well Known Member
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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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
 
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.
 
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.
 
And don't forget....take 20 lbs off the pilot, the airplane performs better and the pilot keeps his medical longer!
 
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
 
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.
 
I fly with 50 lbs ballast in my HR-II. This helps keep the tail wheel on the ground after 3-point landings. I tried with 232 lbs ballast, works even better.

So it's not just about the weight, but where you carry it as well. I have already moved my battery back behind the baggage compartment to help with the c of g, and I use the stock (heavy) Van's tailwheel. It might be better to clamp a zinc anode (for weight) on the stinger.
 
Off topic

If you are trying to build an award winner, you will get dinged if the judges cannot see the rivets. Aluminum airplanes are supposed to have visible rivets and if a judge can't see them he assumes the builder is hiding something.
 
If you are trying to build an award winner, you will get dinged if the judges cannot see the rivets. Aluminum airplanes are supposed to have visible rivets and if a judge can't see them he assumes the builder is hiding something.
Experimental aluminum airplanes are supposed to look how ever the builder wants them to look. A judge should look at the quality and not let their own opinion into their judging. I know that is just a dream and the chance of having open minded judges is zero. But, that is just my opinion!
 
Experimental aluminum airplanes are supposed to look how ever the builder wants them to look. A judge should look at the quality and not let their own opinion into their judging. I know that is just a dream and the chance of having open minded judges is zero. But, that is just my opinion!

My co-builder/girlfriend was not impressed by the 'expert judges', she wanted to build a plane she liked. She has fillled every visible rivet with Superfil. For the complete airplane, we used 32 oz., and the majority is of course sanded off. I actually think we saved some weight, by not filling the rivet grooves with much heavier paint.
 
Light components

Don't forget the lightweight starter, battery, alternator and Magnesium Sky Dynamics flywheel, depending on current equipment this could save 20 lbs. In the last year this pilot lost 34 lbs, 10lbs of it after buying an RV-3A which is also going on a diet :)
 
Don't forget the lightweight starter, battery, alternator and Magnesium Sky Dynamics flywheel, depending on current equipment this could save 20 lbs. In the last year this pilot lost 34 lbs, 10lbs of it after buying an RV-3A which is also going on a diet :)
I'm at approx 60 hrs and 6 mos on the Ballistic lifepo4 battery. Saved me 6-7 lbs, with no reduced starting performance, and uses same alternator/system components as with the gel lead-acid used before.
 
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