[hohocc]

I'm about to start a 6 project but am new to aluminium aircraft construction. Aside from the ongoing debate on priming or not, and watching the amount of gadetry installed, does anyone have any good advice on keeping weight down? Apart that is from going on a diet...
Thanks!

 

[Vlad]

Craig wellcome!

There is a wealth of information on this site on weight reduction. Do search. Build it light and keep it simple - that the message from RV gurus here. You do not need to go on diet yourself..

 

[L.Adamson]

My (newly flying) 6A is on the heavy side at 1172 lbs. It does have an older/heavy starter, along with six pac instruments that are heavier than the new electronic panels. It has 2 axis auto-pilots too, along with an oxygen tank behind the right seat.

But.................it's fast! It easily outdistances the two 9A's I fly with, and is only slightly slower than another 6A. But then I don't have the main wheel pants installed either. I'm still breaking it in.

It has a Lycoming 0360 AIA, and Hartzell C/S prop. Personally, I'd rather have some of the necessities for a pleasurable long distant cross-country; than keeping it light, with a small engine and fixed pitch prop. But that's me..

L.Adamson

 

[hohocc]

Thanks for your responses gents.
I'm probably tending more towards simple and light, but each to their own on that issue as it's a purely personal choice. I've done a couple of searches on weight reduction/weight control and there's a lot of responses, I just need to sort through them!
Any other comments would be appreciated...

 

[Mel]

I see under your "interest" that you are looking at the RV-6. My RV-6 weighs in at 1031 lbs. with a hopped up O-320 and a 3-blade Catto prop. It will cruise at 201 mph TAS @75% power. I typically cruise at about 65% at just over 170 mph and 7.3 gph.
Yes, the other guys are faster, but a light airplane flies so much better. (And cheaper to build and fly)
And BTW, if you think you have to have more power and a C/S prop; I fly out of a 1500' strip in Texas, even in the summer, without problems.

 

[rvbuilder2002]

My (newly flying) 6A is on the heavy side at 1172 lbs. It does have an older/heavy starter, along with six pac instruments that are heavier than the new electronic panels. It has 2 axis auto-pilots too, along with an oxygen tank behind the right seat.

But.................it's fast! It easily outdistances the two 9A's I fly with, and is only slightly slower than another 6A. But then I don't have the main wheel pants installed either. I'm still breaking it in.

It has a Lycoming 0360 AIA, and Hartzell C/S prop. Personally, I'd rather have some of the necessities for a pleasurable long distant cross-country; than keeping it light, with a small engine and fixed pitch prop. But that's me..

L.Adamson

This is not meant as a critical poke at Larry (everyone has to make there own choices) just a datapoint for comparison.

My RV-6A with an O-360 A1A currently weighs 1042lbs. That is with temperfoam seats all fairings, standard six pack using vacum gyros. I have a com/gps, transponder, and rocky mountain engine monitor.
I do not have a two axis autopilot, O2 tank, or a constant speed prop (Sensenich FP metal) and the airplane is not yet painted. Paint will add 12-15 lbs

 

[L.Adamson]

This is not meant as a critical poke at Larry (everyone has to make there own choices) just a datapoint for comparison.

My RV-6A with an O-360 A1A currently weighs 1042lbs. That is with temperfoam seats all fairings, standard six pack using vacum gyros. I have a com/gps, transponder, and rocky mountain engine monitor.
I do not have a two axis autopilot, O2 tank, or a constant speed prop (Sensenich FP metal) and the airplane is not yet painted. Paint will add 12-15 lbs

My 6A weight, does include all fairings (although not all installed at the moment), leather seats, weight for an interior, carpet, heavy paint, etc..........

But then I've heard that planes with higher wing loadings, are a bit smoother in turbulence!

Never the less, my 6A is VERY easy to land. After flying 9A's so much, I'm really surprised, just how easy it is!

L.Adamson

 

[hohocc]

There's certainly a lot of variation in weights among the aircraft you folks operate. The lightest I've heard of was by a builder in Australia whose 6 came out at around 950 pounds, but there may well be others that are similar.
My 6 empennage and wing kits are due to arrive in the next week or so, so it's early days but weight control is, in my opinion at least, a priority. I fly for work so see enough of avionics and tv screens there, I expect to have a very basic panel which will help my cause, however I've got lots to learn about construction.
Thanks!
Craig Clapham

 

[gasman]

Craig....... I also like a lite plane. My 6A is at it's best when there is only about 8 gallons left and solo!! I altered my seats and lost 5 pounds. I changed from a Toyota alternator to a PLANE POWER and lost another 4 pounds. Manual flaps are lighter and easier to install. HOOKER twist release seat belts will add weight, Try CROW standard belts.

The one thing that I had a choice, and went with the heaver was my GOODYEAR FLIGHT SPECIAL III 4 ply tires. Smooth as silk and wear like iron.

 

[tinman]

You almost got it in your initial question. The easiest way to save weight on the plane is for the pilot to go on a diet. Total weight is what matters. If you have built a light ship and are a biscuit boy, your performance is going to suffer. Do both your plane and your heart a favor and go on a diet while you build. Happy flying

 

[carguy614]

Think light

Mel is right. My 9A is chubby at 1141. Having flown a lighter ship, I can tell you the difference is astounding in the way the lighter plane flys and handles. One thing I am not sorry about are the seats. Get comfortable at any weight penalty. Install only the gadgets that you really need, and keep your primer coats light on the inner structure. My next plane will be a RV9, and I will pay way more attention to how much it will weigh when complete. That being said, I love my plane and will make no effort to lighten it up.
The "grin" is weightless!!

Regards...Chris

 

[Rick6a]

Weighty Subject

The thing about weight claims: I am naturally suspicious of empty weight claims because there can be huge errors in weighing equipment. For instance Ruggles scales...cheap and widely available are little more than bathroom scales modified with arms to multiply the indicated weight. So inaccurate, I had to pull my -6A on and off Ruggles scales 10 separate times.....each event offering a different reading. The lowest indicated weight came in at 1065 pounds! In the end, I simply averaged numbers that fluctuated all over the place and finally settled upon 1098 for W&B purposes.

Because mine was not the only sour experience with those scales, our EAA Chapter 32 voted for and invested in a much better alternative. This time around, I used our digital race car scales to weigh the -8 project with and they seem to be far more accurate. I could not get the indicated weight to vary by so much as a pound.

​

Still, the most reliable numbers would be had by using certified scales and I seriously doubt most RV builders have used certified scales to establish the true empty weight.

 

[Mel]

The thing about weight claims: I am naturally suspicious of empty weight claims because there can be huge errors in weighing equipment.
Still, the most reliable numbers would be had by using certified scales and I seriously doubt most RV builders have used certified scales to establish the true empty weight with.

BTW, My 1031 lbs. is with paint and on certified scales.

 

[L.Adamson]

C/S versus fixed -- weight

Many of the "lighter" planes, use a fixed pitch prop. Personally, I wouldn't want one if it was given to me. That's an opinion shared by myself and apparently "all" the other C/S RV flyers that operate out of our 4600' msl airport.

And yes, some composite C/S props are lighter than my Hartzell, but at a higher cost.

L.Adamson -- RV6A

 

[Mel]

Fixed pitch is fine.

If you want a constant speed prop, great. Then by all means get one. They are very nice. But don't think you HAVE to have one. There are literally thousands of RVs flying with fixed pitch. I have flown my -6 out of Leadville, CO (9926' msl) with a tired 150 hp engine and a wood F/P prop in the summer with no problems.

 

[hohocc]

Here in New Zealand there are very few airfields I'd expect to use that are higher than about 1500'amsl, so in my opinion at least an 0320 with fixed pitch wood prop (or possibly fixed metal if it helped the c of g situation) is the way I expect to go at this VERY early stage. In a few years I may feel differently, but in all the flying I've done up to now the most enjoyable has been in simple aeroplanes like cubs and tiger moths which are probably basic to the point of being archaic!
Keep the posts coming, I'm lapping them up!
Cheers, Craig Clapham

 

[L.Adamson]

If you want a constant speed prop, great. Then by all means get one. They are very nice. But don't think you HAVE to have one.

Oh..............I HAVE to have one. I'd have gaven up numerous items before doing away with the C/S! Besides, nearly every plane I've flown for the last 15 years has had one...

L.Adamson

 

[rvbuilder2002]

Many of the "lighter" planes, use a fixed pitch prop. Personally, I wouldn't want one if it was given to me. That's an opinion shared by myself and apparently "all" the other C/S RV flyers that operate out of our 4600' msl airport.

And yes, some composite C/S props are lighter than my Hartzell, but at a higher cost.

L.Adamson -- RV6A

It's true that a fixed pitch prop. is lighter than a constant speed but not by as much as you might expect. It is a big solid hunk of aluminum and it uses a steel prop extension and six long 1/2 bolts (assuming an O-360).
I don't know the exact amount but I believe it is inside of 10 pounds. The other factors are no prop. gov., control cable, or gov. drive (if it has been removed).
I think the weight difference between a fixed pitch and constant speed is no more than about 15 lbs total.

 

[N941WR]

...
I think the weight difference between a fixed pitch and constant speed is no more than about 15 lbs total.

Unless you use a composite (wood) prop. My Catto is 9 lbs vs. 40 lbs for a metal FP prop.

The numbers presented on the Van's web site are a good tell. The RV-9 numbers are all for FP prop whereas the RV-7 numbers are all for CS props.

The GW climb for a FP O-320 RV-9 is 1400 FPM and the GW climb for a CS O-320 RV-7 is 1400 FPM. (1650 FPM / 180 HP & 1900 FPM / 200 HP)

When you look at the GW cruise speeds for the two different planes, again the -9 has a FP prop and the -7 has a CS prop and both having O-320's, it makes me wonder why anyone would want a CS prop.

RV-7: 192 MPH
RV-9: 189 MPH

Other than doing acro or formation work, I have to wonder if the CS prop is worth the cost, maintenance, and weight.

Before anyone jumps in how their 180 HP RV-6/7/8 trounces 160 HP RV-9's, the differences is more the engine than the airframe or prop.

The question comes back to, how much climb rate is good enough for your mission? A Cessna climbs at maybe 750 FPM at GW, so going up at 1400 FPM with a "low powered" FP RV is just outstanding!

 

[L.Adamson]

When you look at the GW cruise speeds for the two different planes, again the -9 has a FP prop and the -7 has a CS prop and both having O-320's, it makes me wonder why anyone would want a CS prop.

Perhaps it's where we live and fly. See included pic. We fly down this canyon, and up it too! If you think a C/S doesn't make a difference, believe me.... it does!

I know of NO ONE around here, who has owned an RV with a C/S................that would be willing to go back to a fixed pitch. We discuss this fact quite regularly, including EAA chapter meetings, when the question comes up. Naturally, I scream and yell, until the prospective prop buyer is convinced!



L.Adamson -- RV6A

 

[Kevin Horton]

Unless you use a composite (wood) prop. My Catto is 9 lbs vs. 40 lbs for a metal FP prop.

The numbers presented on the Van's web site are a good tell. The RV-9 numbers are all for FP prop whereas the RV-7 numbers are all for CS props.

The GW climb for a FP O-320 RV-9 is 1400 FPM and the GW climb for a CS O-320 RV-7 is 1400 FPM. (1650 FPM / 180 HP & 1900 FPM / 200 HP)

If you use the data from Van's web site as a comparison, don't forget that not only is the prop different, the wing is different too. If everything else is equal, an aircraft with longer wing span will have a higher climb rate than one with shorter wing span. So, an RV-9 should be able to out climb an RV-7, if both had the same engine and prop.

 

[Webb]

Look in mirror

My recommendation, take a good hard look in the mirror. I know that I need to lose 25 pounds (and I'm working on it - heading to the gym this morning). Your heart will appreciate you and you have a better chance of keeping your medical. You might even live longer!!

For the fit folks, you have to put your plane on the diet.

 

[N941WR]

This was posted on Van's first flight list:

From: Kevin McCormick
To: [email protected]
Subject: First Flight
Date sent: Mon, 6 Oct 2008
Serial # 23648 RV-6

After 12 Years 10 months and 23 days my plane finally made its first flight on September 25th 2008.

Empty weight is 944#
Engine 150 HP O320
Wood Prop
Simple steam gauges purchased from Van’s
Normal flight instruments
Manual flaps
ICOM portable radio panel mounted

My goal was to keep it simple and light. It flies like the RV7 I flew when I took my transition training with Mike. I really don’t have anyone to thank, the entire plane was completed by me, every rivet. My wife has never been supportive and still is not. My children were too young when I started and have never had any interest in it.

I do want to thank everyone at Van’s aircraft for the support during the construction.

944 pounds! We all have something to learn from Mr. McCormick!

 

[Kyle Boatright]

This was posted on Van's first flight list:

944 pounds! We all have something to learn from Mr. McCormick!

If that weight includes all the fairings, paint, and a decent set of cushions in both seat, that is an impressively light aircraft. Looking at my 1030 pound, 0-320, wood prop, Piper Cub paneled RV-6, I just don't see any way to get 85 lbs out of my aircraft to match that one. 50, maybe, but 85? Wow.

Estimating the "extra weight" in my airplane and what could be saved by a more weight conscious person:

Carpet 8 lbs.
Too-heavy primer 10 lbs
Too-heavy paint 10 lbs.
Thick cushions 10 lbs.
Heavy starter 8 lbs

Total: 46 lbs.

Subtracting that from my airplane's weight results in 985 lbs. Where does that other 40 lbs of savings come from?

 

[RichB]

This was posted on Van's first flight list:

944 pounds! We all have something to learn from Mr. McCormick!

Reading the rest of his post, I'd say we all have A LOT to learn from Mr McCormick about perseverance. He built it right, took almost 13 years to first flight, and did it without family support. That's hard yards right there.

 

[hohocc]

944 pounds, very impressed!
It seems to me from the posts here weight control (for the aeroplane at least!), is all about the basics, a minimum of gadgets on the panel, prop choice, starter/ alternator options, paint and comfort items inside. Thanks for all your replies to my question, and if anybody has anything else to add I look forward to it.
Craig

 

[whifof100ll]

Catto and Acro

Unless you use a composite (wood) prop.
Other than doing acro or formation work, I have to wonder if the CS prop is worth the cost, maintenance, and weight.

I think the lighter weight prop enhances the feel of an RV-6 and is great for Acro.