Basic RV-3 questions - props, W&B, The Wing

[Saville]

Hi all,

I just joined this forum a few minutes ago although I've been reading it for weeks.

It's time to get my own airplane, and I'm trying to decide between an RV3, RV-4 and RV-8. Each have their own pluses and minuses, as you all know.

I go around and around with all the considerations, and I'll put those in a main forum post.

But focusing on the -3, my reading has turned up several questions. I was hoping someone could answer them.

1) C/S Props

I would like to hang a Constant Speed prop on a -3.

Through reading and watching Youtubes, I indirectly inferred that hanging a C/S prop on a -3 is problematical. It seems to have to do with the Weight & Balance. I watched a video by Paul Dye, and he mentions he wanted a C/S prop but had to find a lightweight one. So he hung a carbon fiber 3 bladed prop on his -3.

That sounds expensive. Is the number of C/S props, that are light enough for a -3, limited such that I have to pay huge dollars for a carbon fiber 3 bladed prop?



2) The Wing

I've read a lot about the failures an limitations of the first version of the wing. I've read about the two upgrades to existing wings. I also know that I can buy a QB wing kit for the -3. My questions are:

1) How difficult is it to retrofit a new QB wing to an already-built RV-3? Could it be impossible if tolerances were not strictly kept?

2) The new QB wing has wing tanks. If I want to plumb those tanks in and use them, and NOT use the fuse tank, will that increase my Useful Load?
- If I'm not mistaken, the fuel in wing tanks are not counted against useful load in the other RV's (though I don't really understand why)

3) How hard is it to remove the fuse tank and plumbing if I want to use the Wing tanks only? Would removing that tank pose difficult W&B issues?


Any insight would be helpful.

Thanks!

 

[David Paule]

Welcome to VAF and also to the RV-3 community!

As far as I know, there are two constant speed props that aren't too heavy. One is the Whirlwind 151 at about 28 pounds, and the other is the MT at about 31 pounds. I don't know if those numbers include the governor or not, so the total installed weight might be higher.

What I don't know is the installed weight of a fixed-pitch prop. It's more than just the prop, I do know that.

As far as for carbon, most non-metal props are carbon, at least in part, these days I think.

I've had a four-seat airplane now for a few decades, and am building an RV-3B. I would not consider a single-seat airplane if I didn't already have a capable airplane with more seats.

Dave

 

[BobTurner]

Hi all,
- If I'm not mistaken, the fuel in wing tanks are not counted against useful load in the other RV's (though I don't really understand why)

Thanks!

This is not correct. However, some builders have installed tip tanks, and not counted that weight against the useful load. The arguement is that it does not contribute to the bending moment of the wing, but rather opposes it. Of course a proper engineering analysis needs to be done to be sure.

 

[Mike S]

Welcome to VAF!

Gregg, welcome to VAF

I suggest you contact the factory about your wing fitment questions.

As far as I know, fuel is counted in load calcs-----never heard of it not being.

 

[Saville]

Gregg, welcome to VAF

I suggest you contact the factory about your wing fitment questions.

As far as I know, fuel is counted in load calcs-----never heard of it not being.

I've never heard of that either but I've read it in a homebuilt forum.

 

[Saville]

I've never heard of that either but I've read it in a homebuilt forum.

ACtually I think it had to do with calculating acro weight

 

[dlomheim]

2) The Wing

My questions are:

1) How difficult is it to retrofit a new QB wing to an already-built RV-3? Could it be impossible if tolerances were not strictly kept?

2) The new QB wing has wing tanks. If I want to plumb those tanks in and use them, and NOT use the fuse tank, will that increase my Useful Load?
- If I'm not mistaken, the fuel in wing tanks are not counted against useful load in the other RV's (though I don't really understand why)

3) How hard is it to remove the fuse tank and plumbing if I want to use the Wing tanks only? Would removing that tank pose difficult W&B issues?

1). I don't think it would be very "difficult" if you have previous experience building RV's or something similar and drill out rivets and set it up correctly prior to drilling holes to attach things, etc.

3). The fuselage tank is easily removed by unscrewing the covering sheet and then simply disconnecting it. I could pull mine in less than :20 if I needed to. Regarding weight and balance issues there are quite a few flying without the fuselage tank and wing tanks only so that shouldn't be a show stopper...

Doug Lomheim
RV-3A

 

[Andy Hill]

That sounds expensive. Is the number of C/S props, that are light enough for a -3, limited such that I have to pay huge dollars for a carbon fiber 3 bladed prop?

There are RV-3s flying with the Hartzell (=heavy) C/S Prop.

However, the principle of what you are saying holds true... to get near Vans' design weights (Max AuW, Max Aeros weight) is difficult using today's "standard" equipment. NB Vans' original RV-3 was )-235/290 (?), light wooden FP prop, no electrical system (hand swing). Yes - a FP prop might save 10-20lbs over a C/S Prop, but it is quite easy to blow that saving in other areas (lights, avionics, engine).

I think the WW v MT prop weight is closer than stated above, since the WW has had some modifications fitted*.

If I'm not mistaken, the fuel in wing tanks are not counted against useful load in the other RV's (though I don't really understand why)

As above, there is a debate about whether Wing Fuel counts towards "Weight" for the Max Aerobatics weight. Given tapered spars etc., personally I find the argument not sound. The RV-3 argument is closer, since as you say, it has gone from the fuselage tank to the wing tanks. I doubt you will get a watertight answer either way*.

*Best researched source I would say is Randy's website, with specific references to these points.