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Old 01-01-2022, 07:34 AM
penguin penguin is offline
Join Date: Jan 2005
Location: England
Posts: 1,166
Default RV-6 on a diet

My RV-6 weighed 1127lb when I bought it – rather too much but there were some compelling reasons why that was not a deal breaker such as an angle valve motor. When it was built 20 years ago the choices made were entirely sensible, but the world has moved on. It is now time for a diet. The aim is for an empty weight below 1050lb and to shift the empty cg rearwards, currently it is at 69.2” aft.
This project will take several weeks, some of the parts are still in transit!
I have made a prediction for the weight that can be saved, current estimate is 1035.4lb empty weight. Yesterday I started by removing many of the engine accessories and weighing them, so I know most of the weights in the attached table are correct. Going to be interesting to see what the eventual result is. I'm not smart enough to format a table here so have attached a picture of what I am planning.
Headline items that save the most weight
Prop, Hartzell removed Whirlwind fitted (-23lb)
Battery, PC680 removed Varley Lithium fitted (-10lb)
Cowling, old uncored version removed new cored cowl fitted (-15lb)
Sump & inlet. Lycoming items removed SkyDynamics Maxisump fitted (-9lb)
Alternator, regular front mount alt removed Monkworkz fitted with light SkyDynamics starter ring (-9lb)
Changes in the panel, including new transponder (-12lb)
Lighting changes, replacing incandescent with LED (-7lb)
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Old 01-01-2022, 08:06 AM
LouFly's Avatar
LouFly LouFly is offline
Join Date: Sep 2016
Location: St. Louis MO
Posts: 114
Default RV-6 diet

Thanks for posting Penguin. Look fwd to hearing about your results. Couple years ago I decided the the best "bang for the buck" was the accumulated 30 lb off of my own rear end :-).

That done, just replaced battery. Engine component upgrades at overhaul, and panel soon.

How do you tell if your cowling is cored? Have you considered making a mold and doing carbon fiber?
Bob Miller
RV-6A bought flying, GN-1 resurrected & flying
2022 -=VAF=- Contributor
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Old 01-01-2022, 08:11 AM
plehrke's Avatar
plehrke plehrke is offline
Join Date: Sep 2006
Location: Defiance, MO
Posts: 2,043

Good plan.
One thing to check is if your starting weight and CG location is accurate. Is the 1127 lbs based on weighing when you bought it a year ago or is that the original weight when it first flew? It is amazing how much weight is added just due to time passing. I did a few things recently to save 20 lbs and when I reweighed it I only lowed it by 10 lbs. when I tried to figure out why, I looked back through logs and found a lb here and there over past few years added up.
RV-6A - flying 1000+ hours
Donated to VAF yearly since 2007. Why? Because it is worth every penny and more.

There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact. —MARK TWAIN
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Old 01-01-2022, 08:38 AM
penguin penguin is offline
Join Date: Jan 2005
Location: England
Posts: 1,166

Originally Posted by LouFly View Post
How do you tell if your cowling is cored? Have you considered making a mold and doing carbon fiber?
A cored cowl has a 1/4" layer of honey comb between the inner & outer skins. Anything made after around 1999 is cored. Far too much work for too little gain to mould my own, carbon would not save much, and I work for a composite company. I could probably lose 10lb, but I need to get more than that out of the aircraft!.

@Philip, yes, weight always goes up!

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Old 01-01-2022, 09:48 AM
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Dan 57 Dan 57 is online now
Join Date: Sep 2018
Location: LSZF
Posts: 1,153

yes, weight always goes up!
Not always, as gravity will happily demonstrate...

Seriously now, I bought my ship some 3+ years ago, and though it wasn't that heavy for a O-360/3 bladed MT CSP config, had her on a slight diet:
- removed the tail beacon and associated power supply, good for almost 3kg
- glassed the panel with minimal equipment for my requirements, e.g. dual G5 and GNX375, no back-up instruments. Also removed the whiskey compass. Saved about 1kg on the panel
- replaced the tailwheel (Lightweight from Flyboy) and the springs (Lynx), saved 300+ g.
- biggest save yet (probably not applicable in the US...), exchanged the muffler and shaved almost 5kg at once
- SDS engine covers, lighter for sure, but don't remember the figure

On the other side, there were a couple of fatty items added, such as Supertracks for the sliding canopy, a fifth point for the harnesses, and some other gimmicks.

Actual weight is 485kg (1070lbs), but this a simple machine, no AP, no heated pitot, etc.

Still pondering if going for the battery... not too sure since mine is located in the alt box between the PIC and PAX pedals. That would be a nice one, but still 100% convinced about the reliability issue, inside the cockpit.
Another one would be one of those SDS flywheels, they sure look pretty hi tech
- ain't the Destination, but the Journey -
YLL On Tour... the blook:

RV-6.9i #25685, slider, O-360-A3A (carb/dual Lightspeed II), MTV-12-B, HB-YLL owner & lover
RV-4 #2062 HB-YVZ airframe builder
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Old 01-02-2022, 09:14 AM
Doug Eves Doug Eves is offline
Join Date: Dec 2007
Location: Brigden Ontario Canada
Posts: 96

From my recent experience I would recommend weighing your craft with very accurate scales for yourself if you are a buyer and not the builder. Long story short. Bought mine around 2006 and recorded weight was 1098. Over the years I have made many changes which should have resulted in a lighter aircraft. Just weighed it a month ago. 1130. Asked the builder about it. His weight was before the first flight with no paint.
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Old 01-02-2022, 09:20 AM
Doug Eves Doug Eves is offline
Join Date: Dec 2007
Location: Brigden Ontario Canada
Posts: 96

One further observation in my humble opinion. Most of us could shed around 30 lbs and live longer to enjoy flying
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Old 01-02-2022, 08:39 PM
BruceW BruceW is offline
Join Date: Aug 2005
Location: Elk Grove, CA
Posts: 301

I could loose 10-15 pounds off my RV-7.
And I do nothing to change my plane.
Not a New Years Resolution (dont do that), but losing body fat gives me more motivation when I also think I will reduce my plane's gross weight.
Bruce W
RV-1 Mockingbird rebuild, 1997
RV-7 QB, 2010 (500+ hours)
RV-14 working the tail
Elk Grove, CA
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Old 01-03-2022, 12:56 AM
JDeanda JDeanda is offline
Join Date: Apr 2013
Location: Ventura, CA
Posts: 384
Default Airplanes Get Heavier

Mm hmm, airplanes get heavier due to meteorite dust, if nothing else. 1037 lbs. for an RV-6 with a constant speed prop seems pretty good to me. It's surprising how much weight builds up in stuff like leftover wiring when electrical equipment is removed. If somebody does a quickie sand and paint job instead of stripping and painting, it can add as much as 20 lbs. A friend is doing an annual on a Bellanca with 3 paint jobs on it. I wonder what all that weighs? LED lights can often save a bit of weight on their own, especially if you can remove power packs for old timey strobes, plus you can often remove even more weight if you do a load analysis and discover that the reduced electrical land allows smaller, lighter wire. LED landing lights can make a decent improvement. If you do this, be sure you end up with the right value circuit breaker or fuse, BTW. Sheetmetal and fiberglass repairs can add significant weight when they're overdone. Bolts and screws that are too long, using bolts where screws or clevis pins are OK and using full depth nuts where shear nuts are OK and adding extra washers build up weight eventually. I use flanged nuts for low stress fasteners when I can. If you can remove vacuum-driven instruments and the pump you can get several pounds off, plus clearing a pad for a backup alternator or just cleaning up the engine room. Upholstery is heavy. So is sound insulation. Choose (or remove!) those things wisely, Grasshopper.
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Old 01-03-2022, 06:35 AM
Mtherr Mtherr is offline
Join Date: Nov 2020
Location: Montréal, Canada
Posts: 76

When I bought my RV-6A, it was supposed to be 1114 lbs. Once home, I weighted it and it came out to 1136 lbs (!). I was not happy.

I also put it on a diet, first removing a 24 lbs battery and installing one that is better and 10 lbs lighter. Then, mods on instruments panel, replacement of overweight electrical wiring, leds instead of traditional strobes and lights, removal of unused accessories such as the governor adapter on the engine…

I also added weight: landing light, heated pitot and aux battery for avionics.

It now sits at 1119 lbs which is still higher than anticipated weight when I bought it.
Michel Therrien
RV6A "Second Wind" C-GERZ (born N242UL)
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