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Bob Grimstead
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Posted Wednesday, February 4, 2009 @ 09:21 PM  

Steve B mentioned elsewhere that, with odd RF4 fuselages lurking around the place, it might be worth investigating making RF7 wings for them.

I could not see a better heading to post under than 'Modifications', since the RF7 could be said to be a modification of an RF4.

As I understand it, although there is a flight manual, the only RF7 ever built by Sportavia was never actually certified.

At the Gap/Tallard get together in 2007 I met the Italian guy who homebuilt the second RF7. I believe he did it using drawings provided by RenÚ. Maybe RenÚ would provide us with RF7 drawings to homebuild some more examples if we asked him nicely.

I have an RF4 fuselage in my garage owned by Matthew Hill ('Skyhawk 3'). He also has almost all the metal fittings for the wing, salvaged from a crashed French RF4. He also has an RF5 horizontal and vertical stabilizers. Maybe they could be clipped to provide the increased tailplane span mentioned in contemporary Jane's?

Dave Bland has an RF4 fuselage & tail. Like most such airframes, I think this one went through a hedge. I believe there are a few such fuselages around.

It has always seemed a good idea, if wings were to be built for these fuselages, to make them RF7 wings, since they would be (a little) easier to make, being shorter.

Dave Bland and I compared the RF4 and RF7 drawings in RenÚ's book, and you can see it is not simply a shortened wing. There are differences in aileron shape, and fewer spoiler panels. There may be other differences.

Dave thought there might be similarities with the RF47 wing, but being a side-by-side two-place, it would have a wider centre section, also possibly flaps.

I am not a homebuilder, and I don't have enough useful years left to start now, but I would love to see some more RF7s flying around. The 1700cc motor bit is easy -- or 1835, or 2000. I think Nic's original Sportavia RF7 may have a bigger engine these days.

What do you guys think?

Could we build RF7 wings for our RF4 fuselages?

If we do so, the jig would be the big thing, so it would seem sensible to build several wings in the same place.

Yours, Bob

Collin
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Posted Wednesday, February 4, 2009 @ 10:09 PM  

Hello,

The RF7 uses a RF5 style engine mount and also has wings tanks.

http://www.cfiamerica.com/RF7.html

jb92563
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Posted Thursday, February 5, 2009 @ 12:33 PM  

Hmmmmm....RF4D Fuselages are kicking around?

Perhaps I could undertake a wing production in exchange for a Fuselage?

I'd rather build half a plane, plus I would need the fuselage to take measurements in any case.

Perhaps even go with a composite Carbon wing construction.

I could probably enlist help from a guy who is designing/building an HP-24 glider and his aerodynamicist
to evaluate a design if going that route.

Also just going the wood route modeled after the RF4D wing should prove more than strong enough and follow a proven building method/design.

Its always a good idea in aviation to copy proven methods and designs.

I have not heard of any Fourneir wings breaking!?

Just to ask out loud, what do you gain with a shorter wing?

I presume it is for the better roll rate?

What would you loose going to a shorter wing? Bigger loop radius?

Less drag, quicker acceleration, higher dive speed, Higher overall speed?

There is also the question of whether your local FAA would still consider the resulting aircraft features as a motor glider.

There is a JAR-22 spec that defines some parameters that a Motor glider must meet for that category. Local country regulations may vary.

I don't think USA or AUS have adopted that JAR-22 spec, although they may consider it as a guideline.

80kmh stall, 1m/s gliding sink rate, (weight/(span x span))< 3 kg/m

Ray

[Edit by jb92563 on Thursday, February 5, 2009 @ 12:37 PM]

Collin
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Posted Thursday, February 5, 2009 @ 04:00 PM  

Hello,

If a new wing would be made for a RF4 fuselage. I think 10m or 11m acro wing with a 14m winglet tips option would be nice. I am not a good acro pilot, but I have be lucky to have flown some nice planes. Flying the Zlin 526 AFS compared to the long wing Zlin 326/526 models, I like the long wing versions.

Collin

Jorgen
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Posted Thursday, February 5, 2009 @ 05:19 PM  

Hear, hear!!!

Collin, that┤s a great idea. The RF 4 is in my opinion already an excellent glider with agreable handling- although you need an extra m/s climb to get up compared to "real" gliders in its current configuration. Having the option to increase the span would improve the already incredible versatility of the single seat Fourniers to an even more outstanding level.

While we┤re at it, might as well make the option 15m. Glider pilots are a conservative lot, you know...

Take 5(b) just 4 fun/ J÷rgen

[Edit by Jorgen on Friday, February 6, 2009 @ 05:30 PM]

jb92563
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Posted Friday, February 6, 2009 @ 12:10 PM  

Yes, building a convertable wing set makes a lot of sense so you have a 10m wing for acro and tip extensions to 15m for better soaring.

The tail area may limit the span unless the tail is enlarged as well.

Ray

Jorgen
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Posted Friday, February 6, 2009 @ 03:11 PM  

Ray, the SFS-31 Milan is a RF 4 fuselage mated to a 15 m Scheibe SF-27M wing. Already tried and tested....

I used to have a half share in a LS-3-17, a good glider with either 15 m or 17,5 m span. The tips were without ailerons and took about 10 min to hook up. Question is whether the ailerons on a 10 m wing could give sufficient handling for a 15 m span?

Take 5(b) just 4 fun/ J÷rgen

[Edit by Jorgen on Friday, February 6, 2009 @ 05:36 PM]

Bob Grimstead
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Posted Friday, February 6, 2009 @ 11:18 PM  

Hi Folks,

Now I've got you all interested, I believe the Fournier wing ribs are simply cut from plywood. These days, given the template or ordinates, these can easily be computer-cut using high pressure water jets. Ditto with many of the metal components, so that 'just' leaves the spars to be made.

By the way, don't go for laser-cut metal or wood components. The laser burns and hardens the edges of both the wood and the metal, making them hard to work and finish.

Yours, Bob

Bob Grimstead
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Posted Friday, February 6, 2009 @ 11:31 PM  

For those of you interested in a carbon-fiber derivative...

and how about this planned motor -- fuel injection system and dry oil sump - nothing to modify for inverted flight, 60 hp, and complete (starter, alternator, oil tank...) weight 98 lbs.

www.hexatronengineering.com/prod02.htm

I don't know how far this is advanced, but it certainly looks lovely.
An there's no point in re-inventing the wheel if somebody else has already done the work.

Yours, Bob

Donald
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Posted Saturday, February 7, 2009 @ 08:23 PM  

Quote:
Originally posted by Bob Grimstead... I believe the Fournier wing ribs are simply cut from plywood...

I rather doubt that. I cannot imagine RenÚ in designing such an elegant aircraft resorting to what I think would be an unnecessarily heavy wing construction. Plywood webs to some of the ribs maybe but I would think they are built up with cap strips and intercostals. Mind you, I've not personally had the fabric off mine so cannot cast my mind's eye back and be definitive. Sam Mason would probably know.
Markku
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Posted Sunday, February 8, 2009 @ 04:21 AM  

In RF-4 all the ribs are made of 1,2 mm (Finnish) birch plywood, surounded with 6,5x12mm pine bar.

[Edit by Markku on Sunday, February 8, 2009 @ 04:24 AM]

SteveBeaver
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Posted Sunday, February 8, 2009 @ 01:14 PM    YIM

It's a typical truss rib, cap strips, intercostals, corner bracing blocks etc, but completely overlaid with ply. Of course in each wing, there are no two ribs alike. Some are reinforced with hardwood blocks, some have ply on both side, most only on one side. some have 1.2mm ply, others thicker.

As you might expect, every rib is engineered to perform exactly the job it needs to do and has not one gram more wood than required.

Steve

Bob Grimstead
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Posted Sunday, February 8, 2009 @ 10:16 PM  

Thanks Steve,

My apologies.

I've never seen a rib opened up, only those I can view through the inspection holes.

Silly of me to assume RenÚ would have been so simplistic, and I thought it was odd myself, but I was repeating hearsay (never a good trait in a 'professional' journalist).

Just like the Jungmann/Jungmeister line, Fourniers are masterpieces of functional beauty, with nary a component that is not vital, but absolutely nothing more than is needed.

All hail to the master, again!

Yours, Bob

Jorgen
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Posted Monday, February 9, 2009 @ 05:57 PM  

Absolument,
GrÔce a Mounsieur Fournier! In the "fit 4 outriggers"-thread there is a link to pictures of some ribs that Mike Wollard took during his rebuild of SE-XST, then G-AVNX. The link:

http://www.cfiamerica.com/rf4doutrigger.html

Wood is a lovely material to work with compared to toxic modern composite materials and wooden ribs have a beauty of their own. The Fokker Dr I dreidekker my friend Mikael recently finished has quite a lot of them, but most of those are built from the same template. Fokker was an industrialist (although much of the designwork at Fokker during WW I was made by his welder Reinhold Platz) and acheived a remarkable production pace for that time using rationalization.

Our right honorable Mr Fournier however, is a rare combination of an engineer AND an artist, which might explain why the Fourniers are such fascinating and spirited aircraft. I agree with Bob and bow my head in shame for believing for a moment that there is such a thing as improvments to the Fourniers, you probably all felt the resulting disturbance in the Force

But it still would be fun to try a 15 m wing on my RF 4.....

Take 5(b) just 4 fun/ J÷rgen

Collin
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Posted Monday, February 9, 2009 @ 09:00 PM  

How about adding a winglet to the std RF4 wing?
Markku
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Posted Tuesday, February 10, 2009 @ 04:46 AM  

Quote:
Originally posted by Jorgen

But it still would be fun to try a 15 m wing on my RF 4.....

There was also a less known idea to make such plane, PIK-24 Pileus. Engineering was started in Helsinki University of Technology to mount PIK-20 wings to RF-4D fuselage, the project was started 1977, but it newer got longer than the drawing board.

Donald
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Posted Tuesday, February 10, 2009 @ 09:27 AM  

Isn't that what the SFS 31 Milan is? RF4 fuselage with a 15m Scheibe wing.
milnerd
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Posted Tuesday, February 10, 2009 @ 10:02 PM  

From a distance the Milan looks like a simple modification from the RF4D but the execution is a little more complex than that!

In an RF4D the landing gear, seat and control system are part of the one piece wing. The SFS 31 has a two piece wing that connects in the center with a big tapered pin that runs through the top and bottom spar fittings on each wing. The gear, controls and a cockpit floor (the seat) are mounted to the fuselage on a sub spar that runs across the cockpit in the same location as the main spar does in the RF4D. The Milan has a laminar flow wing, one effect of which is that the spar sits further back in the wing. This allows the main spar to lie aft of the sub spar while keeping the center of lift and C of G in the standard location. The wing has locating pins that run across the back side of the sub spar at the front and on the front side of another sub spar that lies across the back of the wing opening. The bar at the back has pins that face forward so when you put the wings on you have to engage the rear pins into rearward facing cups on the rear spar with the wing tips swept back a bit. Once they are engaged you then walk the tips forward to engage the front pin and mesh the spar fittings together. The only thing that holds it all together is the Jesus bolt. There is a little door in the bottom of the seat that allows you to install the pin and hook up the ailerons. The spoilers connect automatically as the wings are installed but the ailerons need to be connected like a K6 with a pin through a self aligning ball bearing with a pair of teddy bear's arseholes to keep the grit out and a diaper pin to hold the assembly together (no tools required). Then a separate belly pan goes on to close off the opening under the bottom of the wing center section. The two gear up wooden skids are part of the cover and probably not as strong as those on the RF4D (mine is missing altogether). The controls run on a rocking beam that runs fore and aft between bearing assemblies on the front and back sub spar and have an odd shape in order to clear the wing spar and the central pin. The elevator pushrod looks the same from the aft end of the wing backwards but the bellcrank assembly and aileron hook up are obviously unique to the Milan in the center section.

The Milan wings are really heavy because they are skinned 3/4 of the way back with 3mm ply over closely spaced ribs in an effort to maintain a laminar flow wing section. For the same reason that is why none of the Milans have the nice standard Fournier wing paint job with the leading edge stripe painted on. It would do an effectively job of tripping the flow. The wing has a lot less chord than the standard wing and a lot higher aspect ratio. It also bothers me a bit that the wing root has no fairings like the standard ship. I am sure that there is an opportunity to reduce intersection drag at the joint with something held on with electrical tape perhaps. But first I have to get it finished and flying again!!! All I need is time and money.

philippe
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Posted Wednesday, February 11, 2009 @ 06:12 PM  

hello.
Its the first time I come in this forum.
Mr FOURNIER accept to sell me the set plans to built my RF4. I had redesigned all the originals plans in DXF files, and cut all the fuselage wood pieces by CNC (router) cut. the following step will be the wing pieces soon.
I hope save weight by use many pieces in carbon for use the aircraft in french rules ULM (ultralight).
I think it's easy to use during building amovible winglet panels for to increase span. I work on it.

philippe

Jorgen
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Posted Monday, February 23, 2009 @ 06:57 PM  

Salut Philippe,
wellcome to the forum, you will find a wealth of information and inspiration here. Sounds like a really interesting project you have started, I hope you could post some pictures when you start building and if you come up with a way to build a wingpanel for the RF4 you will, as you can see, have a lot of interested Fournierpilots breathing down your neck and drooling over your drawings....

Take 5(b) just 4 fun/ J÷rgen

[Edit by Jorgen on Tuesday, February 24, 2009 @ 04:44 PM]

eugenio
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Posted Thursday, February 26, 2009 @ 03:33 PM  

Please don't ruin a RF4 putting on it a RF7 wing. I had the opportunity to fly the RF7 with the L2000, and I think there is no comparison with the RF4. I also flown the RF4 with the L1700, and I can tell the speed and the climbing rate are practically the same, so as the cruise speed.
RF7 has unbalanced aileron so it's much more stiff, you cannot control it with only two fingers like the RF4 (it's much more like the RF3). Obviously with a shorter wing you can put on it some more G, but why you must put G's on it? It's not definitely an Extra 300 (or something similar) it's a Fournier.

ciao

Eugenio

Jorgen
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Posted Friday, February 27, 2009 @ 03:20 PM  

Ciao Eugenio,
per piecere, I was wondering what you thought about the blasphemy expressed in this thread as a Fournier purists. Good points as usual, Eugenio and valuable opinions on the RF 7 since not that many has flown it.

Since I know your a glider pilot I wonder what your views are on the SFS-31 Milan? Have you flown it and if so, what do you think of the Milan compared to the RF 4? Anyone else who has flown both?

Take 5(b) just 4 fun/ J÷rgen

eugenio
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Posted Friday, February 27, 2009 @ 04:24 PM  

Sorry I never flown a Milan, but I think it should be similar to a K14 that is a K6 with an engine. But again my thougt is the RF4 is the best, it's not a glider because you need a very strong lift to soar, it's a RF4, that's all. My idea is that if you want to do gliding you should use a glider and if you want to go around economically you can use a TMG, that is a Fournier, with the same licence but with two different machines.
Another thougt is that you can do gliding with a cheap glider (you can find old gliders with less than 3000 euros) in a safer way (landing a glider out of airfield is easier than a heavier TMG) and with the possibility to derig it in a few minutes, and last but not least if you destroy it you loose only 3.000 euros instead of 30.000.

This is my belief and that's why I have gliders and motorgliders plus the tug to tow the gliders

I take advantage of this message to invite all to see our new website www.avag.it eventually renewed and working again. Please join also our forum.

ciao

Eugenio

Bob Grimstead
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Posted Monday, June 5, 2017 @ 04:21 AM  

I started this thread because there are some spare RF4D fuselages about. This one is at Nympsfield in west southern England in May 2017. It belongs to Dave Bland, but I don't think he wants it any more. He thought it had already been burned!

Matthew Hill has an elevator, a rudder and an aileron, I have spare cowlings. There is an unused fin hanging completely irrelevantly on the wall of a museum in Shoreham. I have a spare 1,400cc Rectimo engine with carburettor & magneto in Australia plus a surplus propeller, a bent spinner and a cracked canopy (with frame).

I already have a big Fournier rebuild project under way so I shall have no time for a project like this.

Surely somebody out there has time and energy enough to combine these components into an RF4, RF7 or something?

--------------------

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