RV CHROMOLY AEROBATIC HYBRID

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Snaproll

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Could some of the experts advise on the likely challenges of attaching Vans RV4 wings and tail to a purpose built steel tube fuselage. The wings and tail are locally available, and I prefer the safety of the steel tube fuselage and only require a single seat, so am considering a hybrid - possibly powered by a small radial. All thoughts welcome.
 

wsimpso1

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It is a new airplane. It won't have much capability beyond the RV4, with all of the added work of designing and figuring out the build for the fuselage and systems. Should make for an interesting airplane. Have fun!

Billski
 

BJC

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You may want to define what you mean by “aerobatic”, as well as empty and gross aerobatic weight.


BJC
 

Snaproll

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As aerobatic as an RV4 (+6g -3g) and slightly slower, stronger and heavier was what I had in mind. There's also a 150hp radial available not far away, so it should be slightly less slippery than the RV with a round FWF. What would be the best method for mating the aluminum empennage and wings to the tube fuselage ? Thanks
 

BJC

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Does Vans still advertise +6 / -4 g?

The g ratings will be less with a heavier fuselage than an RV-4.

I’m not familiar with the spar carry-through details on the RV-4, but you might consider designing a welded 4130 carry-through that would accept the RV bolting pattern.

You might also want to look closely at the existing wings for strict compliance to the design. Some early -3’s were lost in aerobatics flight due to (IIRC) rear spar attachments that did not comply with the design. Note that the -3 spars were redesigned after that.

Which radial? My understanding is that neither the Verner nor the Rotec is aerobatic.


BJC
 

TFF

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Technically the RV1 was 4130 Playboy fuselage with aluminum wings. RV 3 got rid of the 4130. You are not going to save the weight you think you will. If you plan to use one of the Australian radials, they come apart with aerobics( aerobatics too), unless they have changed something. There is an RV8 flying with one in the US. Looks cool; but is about 15% down on performance compared to regular.
 

lr27

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If you're worried about safety, consider that the RV-4 has had more real life testing than you could ever do.
 

wsimpso1

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As aerobatic as an RV4 (+6g -3g) and slightly slower, stronger and heavier was what I had in mind. There's also a 150hp radial available not far away, so it should be slightly less slippery than the RV with a round FWF. What would be the best method for mating the aluminum empennage and wings to the tube fuselage ? Thanks
Learn how to use paragraph breaks... I do not mean to be a grammar Nazi, but you have no less than five topics here. Paragraph breaks help out your readers, who you are asking for help with your questions. And use of paragraph breaks forces you to edit the topics into more coherent chunks.

The round engine does not have to be more of a lump than an O-320, although it might be.

The round engine does not need to be awful on drag either, with a well designed cowling...

Why stronger? Is there something wrong with the RV4 strength?

You have to hold in-flight weight to RV4 levels or less to be good to RV4 g's - otherwise using RV4 g's puts more load on the wing and tail than the RV did. I suspect that you ought to be able to do it with only a single seat in the ship. Even if the fuselage is not shorter, it does not have the back seat stuff and it does not need anywhere near as much CG range which should avoid direct weight and reduce fuselage bending moments. With anything resembling an optimized fuselage, you ought to be about the same or better.

If you do not have the training to do a downtown job on design of a new fuselage, I will suggest that plans building a new RV4 fuselage to include a round firewall and the single seat layout may be a better choice than guessing at a tube and fabric fuselage.

The best method for mating existing wings and tail is in the method they were designed for. You will have to build in the lift supporting structures at the RV4 positions, using their design fastener sizes and locations.

You will need to become really familiar with the locations and connections for the wing, tail, control systems, fuel system, firewall, and intended CG for aerobatic flight, then mimic the connections, systems, and CG if you want it to take advantage of all that is known about the RV4 as an aerobatic ship. Otherwise, there is not much point in the scavenged wings and tail.

Billski
 

Snaproll

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Ok, very helpful - thanks guys.

Radial is out due to non-akro capacity and tendency to "come apart"!

Scratch building aluminum fuselage as per plans and deleting rear seat appears to be the preferred option.

Other option is buying Harmon Rocket 2 fuselage and wing components.

(NB - one sentence per paragraph as per previous request)
 

mcrae0104

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If you only need one seat, check out the SPA Panther also.
 

Toobuilder

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Not sure what the Rocket fuselage is going to do for your mission other than add weight. Its longer than the -4 in the rear seat and more structure up front to handle the 540. The Rocket wings are primarily RV-4 with the spars clipped and ribs re pitched. The Rocket is aerobatic strength, but has a much higher wing loading than an RV. Seems like that would be counterproductive to a competition aerobat.
 

Snaproll

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Yes, I agree. That was just an overpriced afterthought.
It's either scratch RV4 fuse or 4130 tube if I can get some hands on expert assistance, which may happen depending on other commitments.
I don't think there will be much weight difference either way - a dr107 fuselage is very light and this would be slightly longer but otherwise similar dimensions.
There would be more of a good feeling with completing a custom fuse than a kit.
Importing anything at the current exchange rate is a non starter.
 

TFF

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A DR107 is way shorter than a RV4. The 107 is a nifty plane. If I was really wanting a true aerobatic airplane, it is much better than a RV. RVs are great at doing every category good; it is not great at any specific category. Something like the 107 has room to grow skills; at some point a RV will become a hindrance when it comes to high end aerobatics.
 
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