N941WR

N941WR

Legacy Member
In a number of threads there have been some good tips on how to build a light RV and it would be cool to pull them all together.

Without getting into arguments about which is better on such things as CS props vs. FP, wood vs. metal, auto fuses vs. CB's, could we just list the things that you have done which you feel provided weight savings.

Then maybe someone might pick the best of these things and build a supper light RV.

Here is a list of things I feel helped me keep the weight down:

Tip-up taildragger
Took advantage of every weight savings called out for in the plans
Wood Prop
Small engine
Lightweight starter
Duel P-mags
No vacuum system
Electronic flight instruments
Simple electrical system
Simple VFR (one radio, transponder, intercom, handheld GPS)
Limited the interior to paint and seat cushions
Automotive flasher for the strobe power supply
LED position lights

995 lbs Empty weight (It gained 5 lbs with the autopilot installation.)
 
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RV-6 N168TX

N941WR said:
In a number of threads there have been some good tips on how to build a light RV and it would be cool to pull them all together.

Without getting into arguments about which is better on such things as CS props vs. FP, wood vs. metal, auto fuses vs. CB's, could we just list the things that you have done which you feel provided weight savings.

Then maybe someone might pick the best of these things and build a supper light RV.

Here is a list of things I feel helped me keep the weight down:

Tip-up taildragger Ditto
Took advantage of every weight savings called out for in the plans Ditto
Wood Prop Ditto
Small engine Ditto
Duel P-mags Slick Mags
No vacuum system Ditto
Electronic flight instruments Ditto
Simple electrical system Ditto
Simple VFR (one radio, transponder, intercom, handheld GPS) Ditto plus 2nd com
Limited the interior to paint and seat cushions Ditto
Automotive flasher for the strobe power supply Aeroflash
LED position lights
Click to expand...

Manual trim (pitch & Roll)
Manual flaps
No autopilot
Empty Weight w/paint.....1028 lbs.
Flying beautifully for almost 16 years.
 
Don Jones said:
Automotive flasher for strobes???
Click to expand...
Use something like this SkyBright sytem:
img-0959m.jpg
 
Other tips:

Make all radius on bulkheads and ribs large radius. (Keep minimum edge distance from the rivet hole on the two sides that get cut off.)

Replace AN960 steel washers with AN960PD aluminum where ever possible. Use AN960-XXL and AN960PD-XXL when ever you can.

Use MS21042 all metal lock nuts instead of AN365 (MS20365).

Use the correct length bolts. Do not use bolts that are too long with washers to make them work.

Two saying from 'other' aircraft designers have about building airplanes.

"Only build it as strong as necessary but as light as possible." John Thorpe

"A simple test for everything that you put in the airplane that the regulations do not require. Take the item that is not require in you hand. Throw it up in the air. If it does not come down, it is ok to put in the airplane." Burt Rutan

These are things that I did that come to mind.

My airplane is 66 pounds heaver than Mels and I have a constant speed prop, autopilot, full Gyro panel, IFR radios, and car stereo CD. Would not do the gyro panel or full IFR radios if I were doing it again.
 
Mel said:
Manual trim (pitch & Roll)
Manual flaps
No autopilot
Empty Weight w/paint.....1028 lbs.
Flying beautifully for almost 16 years.
Click to expand...

Actually Mel,
The manual elevator trim (at least the standard cable supplied by Van's) is heavier than the electric trim. The manual aileron trim is lighter.
 
rvbuilder2002 said:
Actually Mel,
The manual elevator trim (at least the standard cable supplied by Van's) is heavier than the electric trim...
Click to expand...
I've wondered how this all nets out? The servo and wire are lighter but then I had to add quite a bit of lead to balance the elevator that has the servo in it. Oh, and then there is the speed controller and wiring. Kind of hard to figure out.
 
Much ado about not much?

Mel said:
Manual trim (pitch & Roll)
Manual flaps
No autopilot
Empty Weight w/paint.....1028 lbs.
Flying beautifully for almost 16 years.
Click to expand...

My -7A before paint and interior was 1051# with an IO-360. Add 20 pounds for that to Mel's 1028 and the difference is 3 lbs. Full GRT instrumentation and strobe pack but no "430". Keep in mind that the 7's wings are longer and 3 tail planes larger and electric flaps and manual pitch trim and installed wing trim. But I did nothing special - did not even drill the lightening holes in the VS spar.

However, I later added paint and interior and weighed 1129#. It's a heavy, full interior with Oregon Aero cushions. FYIO.

My thought would be, if I cared much, to skip the paint, alodine the interior as did Roberta and use lightweight cushions - maybe inflatable like the old Morgan automobiles. Helium? That's the big stuff.

My point is that all the tips in this thread are valid but I don't see that they produce much weight savings. Maybe I'm just not enough of a perfectionist. For most flights if I really want to save 75 pounds I can just leave out 12 gallons of fuel and still accomplish the mission quite well. Or just fly with a smaller passenger!

This is not aimed at Mel (who I greatly admire) but his numbers were convenient for this reply.
 
YEP!

rvbuilder2002 said:
Actually Mel,
The manual elevator trim (at least the standard cable supplied by Van's) is heavier than the electric trim. The manual aileron trim is lighter.
Click to expand...
I understand that. I was simply stating what I have. Manual trim is one of the things I chose in spite of the weight.
 
Mel said:
I understand that. I was simply stating what I have. Manual trim is one of the things I chose in spite of the weight.
Click to expand...

Yesterday, it was climb above the clouds, descend below the clouds; reduce airspeed to maneuvering speed. All this.........over and over! And once again, I thoroughly enjoyed my electric elevator trim switch, which is conveniently right on the stick.

However, when talking to another aquaintence that went on this same trip with a manual trim, he stated that he actually only reached down to trim a few times.

Perhaps I just like to "trim" too much? :D

L.Adamson --- RV6A
 
N941WR said:
In a number of threads there have been some good tips on how to build a light RV and it would be cool to pull them all together.

Without getting into arguments about which is better on such things as CS props vs. FP, wood vs. metal, auto fuses vs. CB's, could we just list the things that you have done which you feel provided weight savings.

Then maybe someone might pick the best of these things and build a supper light RV.

Here is a list of things I feel helped me keep the weight down:

<SNIP>
Click to expand...

Bill,

This is a great idea. Unfortunately those of us going for IFR birds just can't get by with some of the best weight savers, like wood props, or the complete absence of either vacuum or redundant electrical systems.

Without getting too much off topic, what would really help in the pursuit of "lightness" would be any information anyone has on the bare airframe weights (e.g. minus FWF, panel, etc.) of the various models. There is a lot of information out there on the complete weights of various configurations, but without the basic weights is is really hard to do any kind of serious pre-construction weight analysis.
 
Mel said:
Manual trim (pitch & Roll)
Manual flaps
No autopilot
Empty Weight w/paint.....1028 lbs.
Flying beautifully for almost 16 years.
Click to expand...

Not as good as yours but N707DD, RV-7A, came in at 1077 recently.

That's with a BPE "light weight" IO360 (187 dyno HP), Vetterman 4 pipe "Harley" exhaust and Catto 3 blade prop. I don't have the prop yet but Craig told me it weighed 12 pounds so a I hung an Odyssey 680 battery to the extension along with the crush plate and mounting bolts.

Needless to say, I am pleased with this weight. A year ago it came in at 1256 with the Subaru H6, GEN 3 PSRU, 2 batteries, 8 pounds of ballast at the HS, and MT-7 prop. What I am most, most pleased about is the NG weight is now 244, it was 364.

 
JHines said:
Bill,

This is a great idea. Unfortunately those of us going for IFR birds just can't get by with some of the best weight savers, like wood props, or the complete absence of either vacuum or redundant electrical systems...
Click to expand...
Jonathan,

This thread is very helpful to guys like you. Granted you will have a full panel and metal prop, possibly even a CS prop, but the point is, it should show you where you can save weight in some areas so you can add it in others with the options you want.
 
I removed a Toyota alternator and installed a Plane Power unit and lost 4 pounds.

I cut down my seat backs, narrow like the RV4 and just above the cross brace, and also replaced the back cushion with some lite weight foam and lost another 4 pounds and 12 oz.

The narrow seats give more elbow room. Love it........ Manual flaps.... so no dog house between the seats.

I also cut down the arm rests, not to save weight, but to give me 4 more inches of people space. I can store things on the floor behind the passenger seat and just reach between the seats to get what I need. My headsets plug in right behind the pilot seat on the floor. I just reach between the seats and turn them on.

As far as trim, mine is manual. I fly 3 to 5 times a week just for fun and to relax. The airport is 89 feet asl, and I like to fly at 2000 ft asl. With my fp prop, I set my power at 21 and 21 and then lean and trim. I will fly for two to three days without touching the trim at all. I mean for take off, cruse and landing. But when needed, it is only about a quarter of a turn.
 
David-aviator said:
I don't have the prop yet but Craig told me it weighed 12 pounds so a I hung an Odyssey 680 battery to the extension along with the crush plate and mounting bolts.
Click to expand...

I don't know if Craig has changed things, but my 3-blade Catto weighs 16 lbs. Are you sure he didn't give you the weight for a 2-blade?
 
Light and CLEAN

My neighbor is building a 7 and is completely (and obnoxiously):mad: obsessed with building the lightest 7 in the World. He is not taking any metal out per se but is doing everything the plans say to do for lightening. He is only going to paint the glass parts and polish everything else. The only thing else he can do is NOT put in stuff. FYI mine came out to 1123 and in head to head flying with other 7's that are lighter, I'm just as fast. I also have a box built behind my baggage bulkhead that goes to the last bulkhead. (less than 3 lbs)

I think it is just as important to build a very clean airplane. Make sure everything is fit properly. Here are a few things I did to make the plane "clean."
Cowl transition to fuselage as clean as possible, upper gear leg fairings molded into cowl and fuselage, canopy frame (tip up) blended to fuselage, flush canopy latch, targa strip over canopy seam, fairings over rudder cables, wing tips have speed mod molded into edge (this one's a secret), all tail glass is molded in, elevator and stabilizer channels filled at tips, rudder trailing edge is trued, with rivet line filled and glassed to smooth edge, Bob's tail fairing is fit with no gaps and base/clear paint so all tape lines are smooth.

On my new project I have several things I'll be doing to save some weight but I'm not going lose any sleep over them.
 
Caution: Van's Does Not Approve

Right up front: Upon contacting Van's and without any further investigation on their part, (they do have better things to do) an e-mail response sort of conveyed a general knee-jerk response. They did not approve of me adding lightening holes to the RV-8 flap ribs, rather defensively informing me the kits are carefully designed to be as lightweight as possible.

Nevertheless, a friend and highly seasoned aircraft design engineer examined my idea, ran some voodoo calculations and assured me the plan was perfectly okay. As the builder, the decision was completely mine to make.

Granted, weight savings produced by generating lightening holes in the flap ribs is not much, but it does emphasize that carefully considering weight at every step of construction WILL likely result in an empty weight you can be proud of.

29wpq8w.jpg
 
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Mel said:
I don't know if Craig has changed things, but my 3-blade Catto weighs 16 lbs. Are you sure he didn't give you the weight for a 2-blade?
Click to expand...

The prop is due here on Friday....will be able to answer that question then. Four extra pounds up front won't hurt the CG at all.
 
Fly light

I think a better question is how to fly light.

I submit this...

How much fuel do you fly around with. Full Tanks all the time? for lunch on Saturday - 6 lbs/gal

How much do the tools in your baggage compartment weight, do you fly with this around town, why? Do you break down often?

Is your belly full. Lose weight

Then convert all that weight loss and buy a IO360 and put on a CS prop with a Garmin glass panel

This is what you really want anyway.
Tad Sargent
 
Unless you are going to use a O-320 and wood club good luck. I considered
weight during my entire building time but did not let it get in the way of
what the end goal was. Here is a list of what I could have left out but didn't:
Dual strobe power packs
A million (seems like) nut plates
Tons of adel clamps
Paint (lots of it including clear coat)
Classic Aero seats and arm rests
lights

But in the end, my O-360 w/Blended airfoil CS, AFS EFIS/EMS, 496, SL-30,
GTX 327, Tru-Track Pictorial Pilot, Round gage ASI and ALT equiped RV-8A
was finished just as I dreamed and weighed 1124 lbs (using aircraft scales). Not bad I think. Little over 50 lbs more than the lightest I've seen.

As mentioned earlier, the best thing I could do to lower the weight is go on a diet!
 
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Down side to light weight RV

I just finished my RV-6 after 14.5 years. It's ready to fly and I will be ready after transition training next week in TX with Alex. I kept it light, with paint it is 1009 lbs. This is with an 0-360, plane power alternator, light wt starter, wood prop, basic seat chusions, electric flaps, manual trim, taxi and landing lights, strop/nav lights, etc. Great, I was real happy when I finished the weighing. Then I started to do the wt and balance calculations and realized much of my light weight components were up front. With so much light stuff up front I have to limit my baggage capacity if I plan to fly with minimum fuel. With my wife and I, 48 lbs will be the maximum baggage we can haul and still stay within the CG limits with low fuel. I would have had more baggage capacity if I had went with a heavier alternator and starter. When I save a few more pennies and get a constant speed prop my baggage capacity should increase by 20 lbs. Still happy with my plane and will be even more so after next week.

PS: I lost 10 lbs in the last 2 months trying to finish the plane and worrying about the inspection (passed). 15 more and I'll be at the "standard pilot" wt.
 
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Chino Tom said:
....... weighed 1124 lbs (using aircraft scales). Not bad I think. Little over 50 lbs more than the lightest I've seen....
Click to expand...
Tom,

Our planes are somewhat similar in how they are fitted. For comparative purposes, my example also includes an IO-360 w/Blended airfoil CS, D100 EFIS, SL-30, GTX 327, Tru-Trak Pictorial Pilot II, Round gage ASI and ALT.

Other weighty items on mine include an IE engine monitor, AOA system, heated pitot, Garmin 496, small fire extinguisher, and the steel tie down rings were attached for W&B calculations.

I too used uncounted nut plates including their use to make all floors and all fiberglass tips and the rudder bottom removable.

Ditto for generous adel clamp useage including their use with clips and hardware to install electrical conduit in both wings.
Flightline Interior leather includes the seats, armrests and stick boots.
One power pack for strobes, nav lights, landing light.
My RV-8 is unpainted, however its airframe still includes almost all the protective blue vinyl which as you know adds significant weight and on the interior, used Akzo epoxy primer extensively.

Biggest difference I see between our planes....obviously, mine sports no nose gear. Coming in at 1106 lbs, like you I am very pleased with the empty weight. :)

As for me, I can stand to lose 15-20 lbs. Now THAT is a hard thing for me to accomplish.

2r23apy.jpg
 
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Rick6a said:
Biggest difference I see between our planes....obviously, mine sports no nose gear. Coming in at 1106 lbs, like you I am very pleased with the empty weight. :)
Click to expand...

I could have saved maybe 10 lbs. I installed a 4" PVC tube and the
associated support structure aft of the rear baggage for flyrods, umbrellas etc... (Gary Sobek during the inspection noted if it were made of aluminum i would have saved several pounds of weight...I"m not that talented!). I used
Chuck Miller's RV-8A as a weight pattern and he was 1106 like you. Also primed (AXKO) the entire airframe (inside). A small Fire ext. is also incuded
in the empty weight. Also have tip (RV-10) landing lights and one Duckworks leading edge light. I guessed 1120 and was close.
 
Abstenance is the best policy

Burt Rutan said it best.... "If you through it up in the air and it comes down, don't put it in".
 
Frank Smidler said:
With so much light stuff up front I have to limit my baggage capacity if I plan to fly with minimum fuel. With my wife and I, 48 lbs will be the maximum baggage we can haul and still stay within the CG limits with low fuel.
Click to expand...

Not sure of your mission, but I have a similar situation with my -6. My limit is 85 lbs. We've been flying it for almost 16 years now, and have never needed more baggage allowance than that. I think the most we've ever carried (except for testing) was about 40-45 lbs.
 
It would be nice if someone would maintain a grid-based list of these things, including the diff between costs and stuff, to see how everything plays into the initial build. Not necessary, of course, but would be nice.
 
Mel said:
I don't know if Craig has changed things, but my 3-blade Catto weighs 16 lbs. Are you sure he didn't give you the weight for a 2-blade?
Click to expand...

The Catto arrived yesterday, it is gorgeous.

It weighs 16 pounds just like yours. I also weighed the Odyssey, the weigh in substitute, it came it at 15 pounds. My aircraft weight is not changed much substituting the prop for the battery at the extension. :)
 
What About Wing Tips?

These fiberglass wing tips are really heavy! What if you were to eliminate them and form small, contoured tips out of soft aluminum, then had them tempered. I'll bet a good metal man could do a nice job. I recall seeing a mustang ll called little green apples, where that builder made everything aluminum, even the cowl.

One fear is that replacing these fiberglass wing tips with small, contoured aluminum tips might negetively effect the flight characteristics of an RV.

Any thoughts??

Tom
 
Wing Tip Weight

100MU said:
Just how heavy are the wing tips?
Click to expand...

I haven't weiged them myself, but a fellow RV-9 builder said that his compled tips weighed over 8 lbs for the pair. I can't imagine that small contoured aluminum tips would weigh more than 16 to 20 oz each. That would provide a net weight saving of of more than 5 lbs.!!!

Tom
 
Do you suppose the folks who make the tips could be persuaded to make a pair in carbon? That's gotta save a lot of weight and be worlds easier than fabbing some out of aluminum.
 
szicree said:
Do you suppose the folks who make the tips could be persuaded to make a pair in carbon? That's gotta save a lot of weight and be worlds easier than fabbing some out of aluminum.
Click to expand...

Specific gravity of carbon/epoxy is 1.6 versus 1.8 for glass epoxy - assuming minimal resin for adequate wet out. There will be even less difference for more typical resin rich hand laminations.

The carbon would have to be thinner to save much weight and then you'd get into "oil canning" etc. Carbon is good for directional load bearing and stiffness critical applications.

Jim Sharkey
 
RV-9 N194JH

HI all,
I too went thru all the mental gymnastics about weight. I just used common sense in the building. One circuit breaker and that is for the alternator, add up the weight for breakers not to mention the price and you have a good savings of both. Light weight interior, Flight Line has the lightest out there. FP prop from MT, no vacuum system, light weight starter ETC. Panel weighed in at 18 Lbs with SL-30, SL-40, GTX327, PS6000, 4 MGL backup instruments and the MGL Odyssey, along with a TRIO AP and altitude hold.

The bottom line is the total painted weight came in at 1059 Lbs, even better the total price including paint and all else was a tick under $54,000. The AC is a joy to fly and quick. A friend and I went flying the other day he has a 9-A with a CS 3 blade MT 160 HP 0-320 and every bell and whistle you could think of. At 2500 RMP I was cruising along at 185 MPH and he asked if I could give him a hundred RMP. Cool I thought!

My thought is keep it simple and keep it light, you will be rewarded with less problems and thinge to fix in the future, I would rather fly em than fix em.


John H.
RV-9 N184JH
35 Hours and lovin it!!
 
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Lighten your RV

szicree said:
Do you suppose the folks who make the tips could be persuaded to make a pair in carbon? That's gotta save a lot of weight and be worlds easier than fabbing some out of aluminum.
Click to expand...


Do you think that people are willing to pay a premium for a weight savings? What are the cost of Vans wing tips? What percent increase would you be willing to pay for a 5 pound weight reduction?
 
Carbon won't do it

Carbon Fiber could be used to make the tips lighter. With proper reinforcement, I'm sure they could be lighter. The problem is carbon (in this form) is very brittle and would not do well if small rocks, hail etc were encountered. Same with wheel pants. I think epoxy resin and improved layup schedule could make the tips lighter, but cost more. I've discussed this with Van's several times and they say it is a matter of money.
 
If your only goal is the lightest RV ever:

RV3B
No paint (except fiberglass parts)
No electrical. Basic VFR instruments only.
Lycoming O-235
Wood prop

Limited utility, but even with 115hp it would still have about the same power-to-weight ratio as an RV8.

The original, N17RV, had an empty weight of 695 pounds. Incredible! And this was with paint and an O-290... I'll bet someone could build it lighter.
 
Probably not with the B wing....

Floridagator said:
If your only goal is the lightest RV ever:

RV3B
No paint (except fiberglass parts)
No electrical. Basic VFR instruments only.
Lycoming O-235
Wood prop

Limited utility, but even with 115hp it would still have about the same power-to-weight ratio as an RV8.

The original, N17RV, had an empty weight of 695 pounds. Incredible! And this was with paint and an O-290... I'll bet someone could build it lighter.
Click to expand...

Unfortunatley, there seems to be no specific weight data to compare the original A wing with the B wing but I would suspect with the Spar differences, Center Section changes, Wing Tanks, and other modifications that the B wing is quite a bit heavier. Still, I like your lines of thinking!
 
So, at ~1100 lbs dry, how do you add 452 lbs of fuel(42*6), 380 lbs passagers( 2*190), and 100 lbs of baggage and be within the 1800 lbs limit. Above totals 2032. Even at 1050 dry you are still at 1980 lbs
 
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Bobby1226 said:
So, at ~1100 lbs dry, how do you add 452 lbs of fuel(42*6), 380 lbs passagers( 2*190), and 100 lbs of baggage and be within the 1800 lbs limit. Above totals 2032. Even at 1050 dry you are still at 1980 lbs
Click to expand...

I think 42 gallons of fuel weighs closer to 252 lbs.
 
RV7Guy said:
...The problem is carbon (in this form) is very brittle and would not do well if small rocks, hail etc were encountered...
Click to expand...

I've made plenty of carbon aircraft parts, and in my experience the thing about carbon composites being "brittle" is an urban legend.

I'm pretty confident that the wingtips could be made both lighter and stiffer with carbon. All you'd need to do is use a sandwich layup with 1/4" Divynicell H45 or H60 between two plies of carbon and then vacuum bag the whole thing. With 6oz 282 or 284 carbon and some veil cloth you'd probably see a skin weight of a little under 0.40 lbs/ft^2. If I'm calculating the tip area correctly from the published 3-view at around 5.5 ft^2, or about 11 ft^2 when you account for both the upper and lower skins, that'd be about 4.5 lbs per tip or about 9 lbs for the pair.

What it would cost would be a different matter entirely. To make a sandwich part you pretty much have to vacuum bag it, and both the vacuum bagging and the sandwich core add a good handful of time and trouble to making the part. All in all it'd probably be a fascinating exercise, but the overall weight savings would be relatively modest.

Thanks, Bob K.
www.hpaircraft.com/hp-24
 
One problem with carbon tips (besides the effort of making them) is that you can't put an antenna in them anymore. Well, you can, but ... ;)
 
hendrik said:
One problem with carbon tips (besides the effort of making them) is that you can't put an antenna in them anymore. Well, you can, but ... ;)
Click to expand...

That is an interesting point. Do that many people really put antennas in RV wingtips? The space isn't tall enough for a vertically-polarized dipole like you'd want for a com antenna, and what with GPS I'd think that not that many people are installing glideslope antennas anymore. That leaves GPS antennas, which go quite nicely on the turtledeck, glareshield, or in the cowling, ELT antennas that pretty much have to go in the tail, and transponder antennas, which are stubby little blades that can go pretty much anywhere that has a full view of the lower hemisphere.
 
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