[David Paule]

When you're debating whether to get this or that part, and the lighter one is more expensive, how much do you think a pound saved is worth?

Or if you're making the parts lighter, how long will you work for how much weight?

And if you've finished and are flying, was it worth it? Or should you have spent more time and money saving weight?

Thanks!
Dave

 

[Ironflight]

If you take every allowable lightening hole out of an RV-6 and weigh the scrap at the end, you'll have a couple, maybe three pounds of aluminum. If you lost five pounds during the two years of building, you might keep that medical a year longer....

If you can save fifty pounds off the airplane, that's pretty significant. You can get there a pound at a time if you are ruthless. If you're not ready to be ruthless, think about making the pilot healthier!

Paul

 

[rockwoodrv9]

good question

For me, I would spend more time at the gym or less time snacking to save a pound over not installing something I wanted in the plane. Im building a -9 and from what Ive read and by playing with the cool CG spreadsheet I got here, it is almost impossible to get out of CG without going to extremes.

I don't plan on racing, but that could make a difference. I remember racing cars when I was young and stupid - I would even take the glove box door off to save a few ounces.

I guess it depends on your flight profile. Mine is flying for fun and to visit kids - grandkids. I want it to be as comfortable for my wife and I as I can make it. With the -9, weight isn't as critical and I don't see much need to reduce it significantly. Im sure a light plane is great for aerobatics, but that is not my style. Most of my previous flying was in a C-182 and it could haul whatever you could fit so weight wasn't an issue. It was slower than **** (per gph), but we could easily fit a couple bikes in the back.

I will be interested in what others have to say here. Good question!

 

[Kyle Boatright]

The importance is also related to where the pound you save is located. On an airframe that is likely to be tail heavy, eliminating weight in the empennage is very worthwhile, just because it'll have a <relatively> large impact on CG. On the other hand, if all the pound of savings is going to get you is a pound of increased payload, it isn't nearly as important...

 

[roee]

The importance is also related to where the pound you save is located. ...

Yes, very true! In my case, I assign a higher value to saving pounds on the nose, given the history of the -7A nose gear. And in my case, the threshold I've chosen is about $100 per pound of dead weight on the nose. Examples:

1) Prop: Whirlwind 200RV selected over Hartzell. Difference was about 20 lb and $2K. Right on my threshold, but I went for the Whirlwind.

2) Grove nosewheel: Magnesium versus Aluminum. Difference was about 1 lb and $30. No brainer!

3) Tapered fins on ECI cylinders. Supposedly saves about a pound. Cost: more than 10 hours of tedious work to modify the baffles to fit right. Way more than $100 worth of my time. I would rather have lived with the extra one pound of the standard fins.

 

[RetiredRacer]

our 9a is to the extreme.

This is probably not exactly what you are asking, but I'm going to weigh in on this (pun intended )

This is an example of what you can achieve if you put your heart and determination into it. Our 0-235 powered RV9a weighed in empty at 893 lb.
The kit was a quickbuild so the airframe is std (unmodified). Most of the weight saving was in the cockpit and under the engine cowl. An independent weigh-in and inspection was ordered before I could get my certificate, so the weight has been verified.

The reason I did this (and I have had people say "are you insane"): I only have a Recreation Aviation Australia pilots licence (1320 lb MTOW class & no medical required). So at 70 years of age.... and I wanted a Lycoming powered RV..... now we have a 893 lb RA Australia registered RV 9a with 117 hrs on the Tach.

Sure it doesn't perform as well as a 150 or 160 hp 0-320 would, but being light we are happy with the low compression 0-235 C2C performance.



Bob & Robyn Dennis
"Down under"

 

[RV7Guy]

Crazy stuff

One of my neighbors built a 7 that came in at 1025lbs. This was featured in Sport Aviation a couple of months ago when he went for the altitude record and got to 26,900 feet.

His entire goal was to build it light. No lights, autopilot, absolutely nothing extra. Different strokes I guess. I built for comfort for traveling. A few pounds is nothing to get worked up over.

Sadly now all he talks about it the performance and how deficient everyone else's RV is because they are too heavy. Sure he has slightly better climb performance but not that much.

I have offered to go head to head with him on a CC perhaps to Big Bear to quantify any differences. I maintain that the difference, (if there really is any) would likely be miniscule. I have a 7 that weighs in at 1123.

Interestingly, he is claiming performance numbers that are completely unrealistic. He won't take any experience RV people for rides because we are calling BS on his numbers.

So, if you are going to try to save a few pounds, do it but don't get obsessed and miserable over it.

 

[Buggsy2]

If I ever get my -9A built, I will be upgrading from an Aircoupe. That difference far outweighs--heh--the difference I might get from shaving a couple of pounds from the airframe. In other words, I will notice going from 95kts to 160kts, or from 500fpm to 1500fpm...I don't care that it won't be 161kts, or 1505fpm.

 

[rockwoodrv9]

The reason I did this (and I have had people say "are you insane"): I only have a Recreation Aviation Australia pilots licence (1320 lb MTOW class & no medical required). So at 70 years of age.... and I wanted a Lycoming powered RV..... now we have a 893 lb RA Australia registered RV 9a with 117 hrs on the Tach.

Sure it doesn't perform as well as a 150 or 160 hp 0-320 would, but being light we are happy with the low compression 0-235 C2C performance.

Bob & Robyn Dennis
"Down under"

Bob, what a great story. You knew exactly what you wanted and made it happen. I am impressed. At that weight, it may be able to qualify for LSA here.

What kind of performance do you get? Also, do you have any pictures? Did you do anything ratical to keep the weight down other than sparce cockpit and smaller engine? I am still marvel that you can reduce the weight by over 200lbs. WOW.

 

[roee]

One of my neighbors built a 7 that came in at 1025lbs. This was featured in Sport Aviation a couple of months ago when he went for the altitude record and got to 26,900 feet.

His entire goal was to build it light. No lights, autopilot, absolutely nothing extra. Different strokes I guess. I built for comfort for traveling. A few pounds is nothing to get worked up over.

...

Yep, what you're describing that your neighbor did was to optimize for one parameter, weight, above all else. Presumably for the purpose of his high altitude flight. That's what we call a point solution, as opposed to a general solution. That point solution certainly wouldn't optimize utility for most RV'ers. Most of us build and fly RV's because they're great multi-role airplanes, and so we find good compromises between many competing parameters when we build and equip them, weight being only one of those many parameters.

One important distinction to draw when talking about weight reduction in aircraft, is to define what is "dead weight". I would define dead weight as weight that could be removed without any loss of safety, capability, etc. Comfort could also be on that list, to a limited degree. Anyway, a factory-approved lightening hole would be a clear example of eliminating dead weight. So is choosing the lighter of two otherwise equivalent pieces of equipment. In contrast, lights and an autopilot are clearly not dead weight. Eliminating them comes at a tangible reduction in capability and safety. Other items like cushy interiors are in more of a gray area. Anyway, we each define our own priorities and make design trade-offs accordingly.

When it comes to eliminating dead weight though, it does make sense to look at the problem in terms of value per unit weight. The absolute value assigned will naturally vary from one builder to another, due to different mission priorities, etc., as well as available budget. But even the absolute threshold aside, it still makes sense to think of it in those terms. If for nothing else, then to help prioritize intelligently between different opportunities for weight reduction. For example, it wouldn't make sense to spend $200 to save a pound, while forgoing another opportunity to save a pound at the cost of $50.

 

[KRviator]

Ironflight touched on it, but, unless you're already built like a jockey, the single easiest way to lose several (dozen?!?) pounds from your ZFW has nothing to do with the aeroplane and everything to do with losing weight yourself.

You can scrimp and measure and weigh every rivet you put in, use the lightest, most basic VFR equipment, but if you and your Coey still weigh 220lbs or more your fitter, healthier neighbour in his -7, with the Classic Aero heated leather seats and CS prop and 6 ways to Sunday coupled autopilot will perform exactly the same as your spartan example.

I would rather go for a 30 minute run on a sunny afternoon with my ipod playing and then come home and build following the plans than spend that 30 minutes working to get the BEW as light as possible by trimming a few grams here and a couple of ounces there.

There's building light and there's "anal".

 

[roee]

Yep. Good common sense advice. Whether it's weight savings or anything else, better to focus on areas that yield significant returns for relatively little effort & cost, than to waste time on diminishing returns. And regardless of what you do with the airplane, staying fit is always a good thing!

-Roee
145 lb and nothing to lose!

 

[gasman]

Sadly now all he talks about it the performance and how deficient everyone else's RV is because they are too heavy. Sure he has slightly better climb performance but not that much.

So, if you are going to try to save a few pounds, do it but don't get obsessed and miserable over it.

If you ever get to fly a light RV, then you will understand that it's not climb performance, but how nice you can toss it around in the air.

Now, if you are building for X- country flights mainly then extra weight won't be noticed. But if you want to experience what Van intended the RV to fly like, then you will need to build light. I just had someone that just finished an RV3, say that they wondered what it would be like to fly a light one.

I had the opportunity, and it was wonderful.............

 

[RetiredRacer]

At that weight, it may be able to qualify for LSA here.

There is a -9 and a -9a registered LSA in the USA, that is why I went ahead with the project.

My business is building race cars, so for thirty odd years I've been building light. I can not pick up a component and bolt/rivet it on without looking at it to see if any weight can be removed, while still retaining it's strength. So to me it wasn't extra work building light, it was just building.

There is a massive amount of weight saving in the choice of engine, engine bolt on's, prop etc etc. I'll dig up some photo's and work out how to post them (the wife posted our 9a photo, which is on the last page of finished 9/9a's).

I agree totally with what is being said about you own personal weight. When we were racing we kept a strict personal fitness and weight program and we have carried this through, but not as strict

Bob

 

[1flyer]

I was on a program once here at work and a 10 pound weight reduction in the design was worth an extra 5 days vacation, if you could find the time in the schedule to take five days off. I don't remember any takers.

 

[dedgemon]

Want to save 120 pounds for your local flights? Leave half the fuel tanks empty. Makes a huge difference.

Then when you want to actually go somewhere that requires the range (infrequent for most) filler up.

 

[Alan Carroll]

Yep, what you're describing that your neighbor did was to optimize for one parameter, weight, above all else.

True, but to play devil's advocate this one parameter affects virtually other aspect of aircraft design and performance. I've yet to hear of an aircraft designer who wasn't absolutely obsessive about reducing weight, and Van probably leads the pack in this regard. Its precisely because of that obsession that we can get away with adding all sorts of panel goodies, leather seats, heavy paint, etc., and still have reasonable performance.

One of my favorite weight savers is tires. The much-maligned "cheap" tires sold by Van's save something like 4 pounds per set over longer-wearing models like Goodyear Flight Custom IIIs. The tradeoff is that you have to replace them more often.

 

[rockwoodrv9]

There is a massive amount of weight saving in the choice of engine, engine bolt on's, prop etc etc. I'll dig up some photo's and work out how to post them (the wife posted our 9a photo, which is on the last page of finished 9/9a's).

I agree totally with what is being said about you own personal weight. When we were racing we kept a strict personal fitness and weight program and we have carried this through, but not as strict

Bob

Bob, I looked at your picture and tried to copy it into my picture file because it looked so good, but it said I already had the picture! Very, very nice. I love the painted and polished mix. For anyone who hasn't seen what an under 900lbs 9a looks like, here it is:

[/IMG]
I would love to see more of your interior and engine instalation. As light as you are, you could probably slap in a few extra fuel tanks and fly it to the USA. When you do that, make sure to come to Colorado!!

 

[Ironflight]

Want to save 120 pounds for your local flights? Leave half the fuel tanks empty. Makes a huge difference.

That is another gem of wisdom that deserves repeating! The -3 holds 180 lbs of fuel - flying with half tanks saves more than all the "extras" we put itn to make it a cross-country IFR machine. And yup - it makes a difference in handling.

 

[David-aviator]

When you're debating whether to get this or that part, and the lighter one is more expensive, how much do you think a pound saved is worth?

Or if you're making the parts lighter, how long will you work for how much weight?

And if you've finished and are flying, was it worth it? Or should you have spent more time and money saving weight?

Thanks!
Dave

No paint saves weight and money....but it won't win any prizes.

A light weight parallel valve Barrett IO360 with a Catto prop is less money and weight....but it won't win any races.

If it is prize money, in the winners circle, and front page photo ops, money, HP, and paint are the factors that count and that means more weight. None of it is free weight wise or money wise.

Most big time winners at OSH are over weight.

Saving money (and weight) because the retirement plan going light weight.

 

[JonJay]

No paint saves weight and money....but it won't win any prizes.

A light weight parallel valve Barrett IO360 with a Catto prop is less money and weight....but it won't win any races.

If it is prize money, in the winners circle, and front page photo ops, money, HP, and paint are the factors that count and that means more weight. None of it is free weight wise or money wise.

Most big time winners at OSH are over weight.

Save money (and weight) because the retirement plan going light weight.

I have recenlty been "noodling" around and with the insight of a few folks I trust and some research, a clear vision of the obvious developed. Everything is a series of compromises.

 

[RV7Guy]

I have!!

If you ever get to fly a light RV, then you will understand that it's not climb performance, but how nice you can toss it around in the air.

I had the opportunity, and it was wonderful.............

I have flown somewhere around 16 different RV's, including some light ones. They are slightly more nimble but not enough to give up the creature comforts.
As someone noted, people build for different purposes.

Lots of my flights are long ones. I like to arrive relatively rested. Hand flying a RV 1000+ miles in turbulence is not my idea of fun

Fun topic!!

 

[Alan Carroll]

A light weight parallel valve Barrett IO360 with a Catto prop is less money and weight....but it won't win any races.

Actually it might! Some of the faster guys out there are flying with parallel valve engines and/or fixed pitch props, or both. If my only goal was to have the fastest possible plane this is what I'd do, along with stripping out anything not required for VFR flight.

 

[roee]

True, but to play devil's advocate this one parameter affects virtually other aspect of aircraft design and performance. I've yet to hear of an aircraft designer who wasn't absolutely obsessive about reducing weight, and Van probably leads the pack in this regard. Its precisely because of that obsession that we can get away with adding all sorts of panel goodies, leather seats, heavy paint, etc., and still have reasonable performance.

No disagreement there. It makes good sense to eliminate dead weight in favor of carrying functional weight instead (lighting, autopilot, etc.).

Personally, I'd probably leave the leather seats and heavy paint job off that list, since they don't really add "capability". But again I acknowledge that people have different mission priorities. If a heavy interior or paint job add to your enjoyment of the airplane, then that's still more "functional" than dead weight.

 

[mannanj]

Pound

True, but to play devil's advocate this one parameter affects virtually other aspect of aircraft design and performance. I've yet to hear of an aircraft designer who wasn't absolutely obsessive about reducing weight, and Van probably leads the pack in this regard. Its precisely because of that obsession that we can get away with adding all sorts of panel goodies, leather seats, heavy paint, etc., and still have reasonable performance.

One of my favorite weight savers is tires. The much-maligned "cheap" tires sold by Van's save something like 4 pounds per set over longer-wearing models like Goodyear Flight Custom IIIs. The tradeoff is that you have to replace them more often.

A quote attributed to Bert Rutan about individual parts while building Voyager around the World non-stop aircraft; "throw it up, if it comes back down, it's too heavy"!

 

[LifeofReiley]

Build it as light as you can "Safety in mind" and you will be very happy!

 

[L.Adamson]

I have flown somewhere around 16 different RV's, including some light ones. They are slightly more nimble but not enough to give up the creature comforts.
As someone noted, people build for different purposes.

Lots of my flights are long ones. I like to arrive relatively rested. Hand flying a RV 1000+ miles in turbulence is not my idea of fun

Fun topic!!

Noticed the same with my 6A. On the heavier side with "comforts", and yet agile, easy to trim, and surprisingly fast, compared to even a few lighter ones with the same engine, prop. Multi-state cross countries in a "plane" Jane.............is like going cross country on a Harley to Sturgis. Most trailer them, or take their time...

L.Adamson

 

[gasman]

Noticed the same with my 6A. On the heavier side with "comforts", and yet agile, easy to trim, and surprisingly fast, compared to even a few lighter ones with the same engine, prop. Multi-state cross countries in a "plane" Jane.............is like going cross country on a Harley to Sturgis. Most trailer them, or take their time...

L.Adamson

I have ridden my 87 low rider for over 20 years (sounds like Mel) and it has always been the ride, not the destination. If you have to trailer your bike to Sturgis, you don't deserve to be there.

As much as I love a light plane, I would have an auto pilot but pass on the nose heavy, expensive and complicated c/s prop.

 

[L.Adamson]

=As much as I love a light plane, I would have an auto pilot but pass on the nose heavy, expensive and complicated c/s prop.

Then you must have one of those 20lb. "dead" weights stuck up front, to help solve weight and balance. If it doesn't have a C/S...........then I wouldn't want it.

 

[gasman]

Then you must have one of those 20lb. "dead" weights stuck up front, to help solve weight and balance. If it doesn't have a C/S...........then I wouldn't want it.

I didn't think it would take an hour....................

 

[GAHco]

My philosophy!

If I ever get my -9A built, I will be upgrading from an Aircoupe. That difference far outweighs--heh--the difference I might get from shaving a couple of pounds from the airframe. In other words, I will notice going from 95kts to 160kts, or from 500fpm to 1500fpm...I don't care that it won't be 161kts, or 1505fpm.

Change your "if" to "when" and you will get it in the sky much sooner.
Someday we will both be flying!

 

[Nihon_Ni]

I've been thinking about this subject quite a bit. My wife and I aren't exactly Bubbas, but we are 95 percentile for height. Adjusting my personal MGTOW isn't really an option -- I'm only 7 pounds heavier than when I graduated college 23 years ago. So with that in mind, I've begun to think critically about the weight vs cost of all the light weight options. Grove landing gear seems to be high on the list, 17 lbs for about a grand seems like a good trade off, but I'm not sure what other options I should be considering.

I guess I have my next search topic figured out...