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Tail heavy.

Hi guys, happy new year.
I have recently purchased a very well built but rather "rotund" Rv4. It is a rather "vanilla", wooden prop, 150hp basic aircraft. After doing the w & b it has come in at a rather "portly" 1019 lbs. This seems pretty heavy for a pretty basic aircraft but I can't really figure where all the weight is.
My biggest concern is that it is carrying about 66lbs on the tailwheel which is very limiting as to rear passenger weight.
My question is what is a relatively normal weight on the rear wheel. I am aware that it will vary quite a bit from plane to plane, but is there a ballpark figure?
I have inspected the rear end for ballast etc. but apart from a strobe lamp everything is pretty basic. The aircraft has a pretty nice paint job, but wouldn't that add weight proportionally?
Thanks for any help you can offer.
 
The aircraft has a pretty nice paint job, but wouldn't that add weight proportionally?

This doesn't count as help (as in help correcting the issue), but think about where the CG is on the airplane. Let's say it is roughly at the main wing spar. Now, consider the location of the majority of the airplane's surface area in comparison to the main spar. 2/3 of the wing is aft of the main spar, 2/3 of the fuselage is aft of the main spar, and all of the empennage is aft (far aft) of the main spar.

Where I'm going is that paint's weight is disproportionately located aft of the airplane's CG, so a heavy paint job will probably result in an aft CG.
 
Ok I have to ask. That 66lb number is with the tail up in the air right? Not in the three point attitude?
 
This doesn't count as help (as in help correcting the issue), but think about where the CG is on the airplane. Let's say it is roughly at the main wing spar. Now, consider the location of the majority of the airplane's surface area in comparison to the main spar. 2/3 of the wing is aft of the main spar, 2/3 of the fuselage is aft of the main spar, and all of the empennage is aft (far aft) of the main spar.

Where I'm going is that paint's weight is disproportionately located aft of the airplane's CG, so a heavy paint job will probably result in an aft CG.

Thanks Kyle, that makes sense to me.
 
Add lightness to the tail

G?day Peter, you can add weight up front or you can remove weight from the back.

A quick and relatively easy way to remove one pound from the back of your bird is to replace your steel tailwheel spring with a Sky Designs titanium tailwheel spring. Go to: https://www.skydesigns.aero/titanium-tailspring

Given that the only item further aft than the tailwheel spring is the tailwheel itself, it is the second-most effective way to move your CG forward.

BTW: You?ll want to keep your old steel tailspring as it can be used for self-defense in case of a zombie apocalypse. 😉
 
My 1st (purchased) -4 weighed 930 lbs. The one I'm currently flying (also purchased) weighs 910 lbs. 1019 lbs for a wood prop 320 is pretty bad, if it's empty weight (was there fuel in the tanks?). With full fuel, there's not room for a normal sized pilot & still be below acro gross weight.

You didn't mention installed equipment or interior (insulation, carpet, seat cushion material, etc).

Charlie
 
Weight a minute...

Hi guys, happy new year.
My question is what is a relatively normal weight on the rear wheel. I am aware that it will vary quite a bit from plane to plane, but is there a ballpark figure?
Thanks for any help you can offer.

G'Day Pete,
My Sterba Wood Prop equipped RV4 weighed 925lbs empty the day of it's test flight. For it and many others I have inspected over the years I use 50lbs in level flight attitude on the tail-wheel as a good ballpark number for CG ballpark calculations.
There are many ways to help shift the CG on a wood propped Four and reduce weight. Use these suggestions to search for and evaluate your own 4.

1. Odyssey Battery (vice certified aircraft battery) mounted as far forward as possible. I mounted mine on the "shelf" forward of the firewall. R&R of your 26lb aircraft battery to an Odyssey or Lithium will save up to 15 lbs. If it's mounted in the baggage compartment, that will weigh heavily on the TW.
2. Radios, panel, unnecessary items. If you have old radios, power supplies, instruments, round dials, they all add up. Make a list of the heavier ones and look at digital (MGL) or even removal of the unneeded ones.
3. Insulation. Cockpit soundproofing, insulation, thick foam seat cushions add weight. My Four had minimum frills inside and NASA foam seats with light upholstery.
4. Heavy weight Starter/Alt and Mags. A full size Prestolite Starter and certified aircraft alternator weigh nearly twice that of a lightweight version. Bendix Mags weigh twice that of a P-Mag or most Electronic ignitions. There are many vendors out there and you might be able to sell your old ones online.
5. Prop extension. If you remove the heavier starter you can offset the less nose weight by going with a steel prop extension from Saber Mfg.

These are just a few "tricks" you can apply, email me anytime offline and we can start working the issues.
Fair Dinkum...

Smokey
[email protected]
 
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G?day Peter, you can add weight up front or you can remove weight from the back.

A quick and relatively easy way to remove one pound from the back of your bird is to replace your steel tailwheel spring with a Sky Designs titanium tailwheel spring. Go to: https://www.skydesigns.aero/titanium-tailspring

Given that the only item further aft than the tailwheel spring is the tailwheel itself, it is the second-most effective way to move your CG forward.

BTW: You?ll want to keep your old steel tailspring as it can be used for self-defense in case of a zombie apocalypse. 😉

You guys are really from the future? Copyright 2023 ;)

Finn
 
See if you can track down a (Mark) Landoll Harmonic Balancer which bolts to the flywheel. Adds considerable weight up front, smooths out engine vibrations, and gives the lightweight prop a little much neded inertia.
Worked great on my -6, I got about a 50 rpm static increase. Out of production as far as I know, but somebody might have one kicking around.
 
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G?day Peter, you can add weight up front or you can remove weight from the back.

A quick and relatively easy way to remove one pound from the back of your bird is to replace your steel tailwheel spring with a Sky Designs titanium tailwheel spring. Go to: https://www.skydesigns.aero/titanium-tailspring


BTW: You?ll want to keep your old steel tailspring as it can be used for self-defense in case of a zombie apocalypse. 😉
Thanks for the advice, that tailspring price is a bit "eye watering" though. It would cost me about Au$1000 to save 1lb.
I will bare that in mind for Zombie protection but I would have thought that I need to have a chainsaw attached somehow.
 
See if you can track down a (Mark) Landoll Harmonic Balancer which bolts to the flywheel. Adds considerable weight up front, smooths out engine vibrations, and gives the lightweight prop a little much neded inertia.
Worked great on my -6, I got about a 50 rpm static increase. Out of production as far as I know, but somebody might have one kicking around.

If all you need is the weight, there was a 'steel ring' that he sold, as well. No 'balancing'; just what the name says: a steel ring that bolts to the ring gear.
 
Tail heavy

I would love to have a titanium tailspring as well. $$ is the issue for me as well.
 
After I built my -4 I had a aft C/G issue, what I changed was to move the battery to the upper firewall on top of the shelf, I installed a old heavy starter, Installed a 17lbs steel ring on the starter ring and last but not least I started to manufacturer lightweight tail wheels. All of this effort gave me a empty weight of 955# and the C/G was at 70.1". If your -4 is heavy check the wiring for unnecessary service loops, Heavy old avionic, Vacuum systems, Heavy upholstery and such.
 
Decrease versus Increase

Yes, the titanium tailspring is a bit expen$ive but, consider the following:

1. The raw material cost alone is north of $200 ? if a less expensive source for the correct alloy and heat-treat titanium bar could be found, that would allow us to lower the price.

2. Titanium is more challenging to machine than steel - I don't really know this firsthand but when I designed titanium parts for military airplanes, that was what folks always said.

3. Compared to other things that people buy for their airplanes, the tailspring is pretty cheap and, heck, the other stuff you buy adds weight whereas this (and Dayton's way-cool tailwheel) actually reduce weight.

4. Regarding zombie attacks, the ultimate defense tool may indeed be a chain saw but a re-purposed steel tailspring has the advantage of being easier to carry plus it won't run out of gas at the wrong moment. :eek:

BTW: I asked my lovely and charming webmaster about the "copyright 2023" thing and she said that the website builder she uses adds it automatically.
 
I came in at 995 with a O360 and constant speed hartzel. I have 37 lbs on the tail in level flight attitude. It is out forward empty and needs 212 lbs in the pilot seat to get in the envelope. That low ain't NEVER going to happen as long as I own it.

Bob burns
N82rb rv-4
 
I just want to thank everyone for their help & advice on my aft heavy issues. I have removed pretty much everything from the rear and have a light weight tail wheel, with the final weight coming in at 999 lbs.
I do have a question though, when people quote a weight, is that generally to be taken as fully equipped with rear seat, seat back, controls etc. Or is it quoted with that gear stripped out. Because I just can't see where all my extra weight is coming from.
 
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IIRC, it should be ready to fly, but 'empty'. No fuel, or at least no useable fuel, which is effectively the same thing in an RV.
 
Hi Peter, just wondering if your new bird still has the numbers on the side or back in VH.

Cheers Peter
 
Do you have an Auto Pilot pitch servo?

A lot of the Auto Pilot servos are quite hefty. A really easy method to cure an AFT C of G issue is to remove the tail mounted AP servo, and the tail cone mounted ELT while you are back there.

Depending on what your chosen ELT is they can be main spar mounted , or even farther ahead of the C of G.

Along with the above items, your battery and perhaps a Landol ring or plain flywheel ring weight as Dayton and others have suggested are likely the easiest moves with the best effect.
 
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My friend Jim Winings (RIP) fastback RV-4 which I recently sold weighed 918 empty. 180/WW 200RV. Every effort was made to save weight, including the use of titanium hardware.
 
Aft CG

G?day Peter, you can add weight up front or you can remove weight from the back.

A quick and relatively easy way to remove one pound from the back of your bird is to replace your steel tailwheel spring with a Sky Designs titanium tailwheel spring. Go to: https://www.skydesigns.aero/titanium-tailspring

Given that the only item further aft than the tailwheel spring is the tailwheel itself, it is the second-most effective way to move your CG forward.

BTW: You?ll want to keep your old steel tailspring as it can be used for self-defense in case of a zombie apocalypse. 😉

I have a one off sliding canopy on my 4 along with electric flaps motor repurposed from a Cessna so Aft CG has always been a concern to me. I changed engines to an injected 360 from a light 320 still with the wood prop switched to the Earth X battery and recently added the light weight tail wheel and the above mentioned titanium tail wheel spring. I?m right at 1000 Lbs empty but most importantly with minimum fuel I can put 210 lbs in the passenger seat and aft baggage and still be within the aft CG limit.
Pirep on the tailwheel spring : It?s noticeably spongier than the steel one but has no bad habits or adverse handling characteristics, plus it polishes out to a beautiful luster and doesn?t corode. Looks almost like chrome.
 
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