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Paul Millard
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Posted Tuesday, August 26, 2014 @ 07:51 AM  

Hello All
Does any one know of any quality build plans for a RF4 or if not can anyone see a problem in myself drawing a full set of plans in cad and releasing them as free pdf files? As the years have moved on would any one wish to see a RF built from different materials such as aluminum,carbon or a wood /carbon composite. My main brief is that the aircraft is indistinguishable from a RF in outline .Seeing that good wood is quite expensive should more or less balance out with the cost of vacuum bagging a set of carbon wings. I can get some pretty accurate measurements from photos but any help with this would be appreciated. I am pretty experienced with VoltsWagon engines and they run quite nice but I am looking into light weight turbo diesel engines of around 85 hp because of the very low running costs .Any thoughts on this?
Thanks Paul
Donald
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Posted Tuesday, August 26, 2014 @ 01:02 PM  

That's a very ambitious idea and you're probably not the first to think it.

As I understand it the French CFI have copies of the drawings which can be had for the purpose or maintaining the existing fleet but I very much doubt possession of even a full set would constitute any kind of licence to build. Also, the TC holder might have something to say about such goings on. That said, I seem to recollect that there is one homebuilt RF4 underway somewhere. You could probably find it mentioned on this forum.

There are also a couple of gentlemen in France working away on an ultralight RF4, same shape, same idea, more modern approach and a Briggs & Stratton motor, but I don't think it's finished yet. You should be able to find mention of that here too.

If you are talking about designing a lookalike in metal or composite then I'd say you can go right ahead but your's will be a new design that will have to go over whatever regulatory hurdles the authorities require as for any other new type. Just looking like a Fournier won't make it a Fournier. As you are in the UK that will probably not be as easy as it might be in the States or possibly even France but with perseverance I'm sure it could be done.

About motors. The idea of a diesel is appealing in some ways but I'd say 85hp is about two times too much. Many larger VeeDubs have been fitted to the firewalls of RF4's but again you could probably turn up a thread here that talks about this with the conclusion that the original 1200 Rectimo with the 1400cc barrels is about the sweetest combination, and that is reckoned to give about 40hp.

I'm no authority on any of this but you asked for thoughts...

Donald

Paul Millard
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Posted Wednesday, August 27, 2014 @ 10:10 AM  

The plane is a very basic front oblong box , rear triangle with decking design and can easily be r engineered and as you say just because it looks identical it won't be a RF. I suppose I would have to be careful not to call it a copy as not to get into design infringement. I would hope it be considered flattery to produce a plane of identical proportions just to be able to have another option .One area I am thinking of changing is removing the twist in the wings as I don't see tip stalling being a problem and being carbon stiff enough to prevent inherent wing flex (flapping like a bird).
although wood wings are strong enough adding some twist keeps a constant damping force that prevents this but does alter the position of maximum lift along the wing at different angles of attack and obviously increases drag.
Any sketches and photos with measurements will help me produce a basic line plan.I am glad to hear you think 85hp
too much so I can maybe use a small all alloy three cylinder unit of 1.4 liters.The canopy is a item I am not sure about getting new or creating myself , I shall have to find out . How is this for a radical idea ,it is not beyond reason to use a electric propulsion system as weight and power and reliability are no problem.In the model world only ten years ago it would have been quite difficult but now it is becoming the norm so who knows?
If I can't for some reason build my own then I will have to look at an original but I have to admit I am more paranoid about this than knowing what I have done myself .
Donald
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Posted Thursday, August 28, 2014 @ 04:02 AM  

Paul,

We don't know each other so I have no idea of your capabilities in engineering and aerodynamics so while I agree that the fuselage may be a basic box similar to many wooden light aircraft my guess is that it's the wing that counts, not so much the fuselage. How that basic box is finessed and integrated with the rest of the airframe and all its other components is what makes the Fournier a Fournier.

Some years ago I had a conversation with some of the European RF owners on re-building and the consensus was that the wooden airframe was doable but the showstopper was the main landing gear. If you didn't have that single assembly you'd never have a finished aircraft. That was from people who had rebuilt aircraft so presumably knew what they were talking about.

Reverse engineering? Sure, it could probably be done if you had access to an example that could be dismantled, measured and analysed but I don't see that as a small undertaking at all and if you had an example, why would you bother?

3 view drawings can be found online for the RF4 but they just give the basic outlines and proportions, nothing to really underpin a set of construction drawings so it might very well be easier and quicker to go from scratch with a new design styled after the RF4 and your last post suggests that you lean in that direction. I don't see that as a small undertaking either but your mileage may vary.

Other people have imagined using small diesel motors but that's a whole developmental area on its own and while there are many small diesel automotive engines nowadays where are the flying examples to suggest it's even a practicable idea?

Electric propulsion? Sure. Why not? It's being done and it will become more capable and mainstream but all of these changes you speak about, aerodynamic changes, metal or composite construction, diesel or electric power will impact the decisions you will have to make and the compromises you will have to accept resulting in something, while perhaps inspired by the Fournier, not a Fournier.

As for the canopy, I'd say that would be the easy bit.

You may already know of it but http://www.homebuiltairplanes.com/forums/forum.php might be of interest to you.

Donald

Paul Millard
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Posted Thursday, August 28, 2014 @ 10:20 AM  

Donald
Thanks for the reply as I am in the very important early stages and intend a build project of around five years.Yes the single wheel is essential and I have to have it even if I have other options . When I get around to the build I'll let you all decide on the merits of my work. All remarks and comments are important to me before I start on the technical drawings that I will show on this forum if welcome.
Bob Grimstead
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Posted Friday, August 29, 2014 @ 07:17 PM  

Hi Paul,

Re the retractable main wheel, the RF4UL guys had a lighter, better system, with a lighter wheel using wider tyre and a disc brake.

Somewhere I think I have a photo, so I'll try to dig it out and post it.

I've been flying for fifty years, and an aviation journalist for thirty years.

If you want an old man's advice, based on all those years of seeing many, many projects start but then die, I would say build the foam and carbon fibre wing by all means, but use one of the many existing fuselages that are around. The fuselages generally survive accidents, where the wings don't.
I think Dave Bland may have most of one at Staverton, but since he's no longer talking to me, you'll have to approach him yourself.

Re the engine, firewall-forward is always much more than half the project.
Don't muck around with new engines yet.
Build the wing, mate it to a bog-standard wooden fuselage/VW engine/canopy and new mainwheel system, and the project might only take you twenty years instead of a lifetime.

Search this forum and you will see three failed attempts at the sort of thing you're trying to achieve.
The RF4UL, being built with René Fournier's personal assistance is stalled.

Dan Rihn (he who designed and produced the excellent One Design aerobatic aeroplane) said he could make a jig and build RF4 wings, then dropped out of view.

Eugene Zaharenkov showed us their plans of a carbon fibre Fournier.
Nothing more was heard.

Good luck Paul, I really mean that. We all would love to see new Fourniers in production, but do NOT underestimate the mammoth task involved.

Yours, Bob

--------------------
Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

JamesB
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Posted Saturday, August 30, 2014 @ 12:26 PM  

I think Bob is making an important point. Since the end is essentially a copy of or updated RF, you could do it in stages and at least have a flying aircraft while you work on the next stage. Just because you start with an original fuselage, doesn't mean you can't be designing & building one while you fly what you've got.

Brilliant.

Paul Millard
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Posted Wednesday, September 17, 2014 @ 08:20 PM  

Really it is the wings that give me the most to think about.I know the wooden wing is good and strong but here is one element I am not keen on .The main spar is part of a D box system but the leading edge sheeting only stretches
across three ribs at a time where it would be better surely as a full length piece.A D box really only works if it has full torsional strength along it full length.I got this from looking at Markku Kjiski 's wing build.
Any how if I take the carbon route it will be a full carbon frame work without any foam.It is not really more expensive just a lot more work building molds and vacuuming out the skins but at the end you do have the means to quickly replicate if needed.The wheel mechanism I can make either how I used to make T6 aluminum swing arms for motorcycles or a sand cast unit from wood patterns.I am giving myself no time limit on this project as the building is great fun for me.I am sticking with a VW motor but may cast my own twin plug heads and make it 360 proof.Thanks for the reply's I am getting ,I never thought of getting just a fuse so now I'm looking.
Markku
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Posted Friday, September 19, 2014 @ 06:55 AM  

Quote:
Originally posted by Paul Millard

Really it is the wings that give me the most to think about.I know the wooden wing is good and strong but here is one element I am not keen on .The main spar is part of a D box system but the leading edge sheeting only stretches
across three ribs at a time where it would be better surely as a full length piece.A D box really only works if it has full torsional strength along it full length.I got this from looking at Markku Kjiski 's wing build.

Hi Paul
When the D-box plywood scarf joints are properly done (slope min. 1:15), the joint is as strong as the plywood in general, so the D-box is actually as one piece.

Bob Grimstead
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Posted Monday, October 6, 2014 @ 01:18 PM  

Hi again Paul,

I have at last found those photos of the modernised and lightened main wheel system for the RF4UL

I hope these help.

Yours, Bob

--------------------
Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

Roger.Camp
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Posted Wednesday, October 8, 2014 @ 07:23 AM    YIM

Paul, i am presently building an all wood Formula V aircraft with the D wing in wood. And as Markku said it is just as strong. I have seen large models (45 kg and above) fold their wings because the foam/glass/CF didnt meet up to the task. I personally wouldnt go that route. With a would structure you will have time to get out should things go pear shaped, as it will creak, groan etc but with a CF wing there is no warning it probably will be snap and that was it. I am not an expert on CF/Glass but if the choice was there for me i would only go the wooden route.

--------------------
It takes 1.460 bolts to build an aircraft and 1 nut to spread it over the landscape

Bob Grimstead
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Posted Tuesday, April 21, 2020 @ 08:32 AM  

Like all the other bright ideas, I see that this one is now stalled.

That's a pity, because a strong but lightweight new wing is a lovely idea.

Best all stick to the original which is, after all, 13.8g strong, putting it right up there with Extras, Edges & Steinbachs.

--------------------
Flying and displaying Fournier RF4Ds VH-HDO and G-AWGN, building replica RF6B G-RFGB and custodian of RF6B prototype F-BPXV

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