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Nov 10, 2011, 06:31 PM
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mintie's Avatar
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Build Log

Fournier RF4


After many years have decided to build this model.
RCM&E gave a free plan in 1996 and I filed it away for the one day project.
The orginal was 900 gms with cox dragon fly engine and all built out of balsa.
Recently I pulled the plan out again and started to build it out of depron/foam/carbon fiber and balsa where it needed a bit more strength.
The wings are hot wired white foam and covered in news print glued on with 15% water / PVA glue.These turn out very stronge and light.
Fuse is some balsa frames with sides and decking all done in depron.The turtle deck rolls very nicely in depron.
Elevator is depron with a carbon spar and the rudder and post are depron with a balsa spar.
Wings are mounted with a dowel and small bolt.Done away with the orginal idea of rubber bands.[ dont like then]
wingspan 1370mm[54in] power blue wonder 1700 with a 3s 1300 battery,servos HXT 900 x 3.
At this point the weight is ,wings 103 gms,fuse is 110gms. Looking good for around 400 gms .we will wait and see.
Last edited by mintie; Nov 10, 2011 at 07:54 PM.
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Nov 10, 2011, 09:46 PM
Retired CAD guy
birdofplay's Avatar
Looks like a nice build and a nice manageable size too :-)

RCG member , " nostep " , did an RF-4 build in the Scale Sailplanes forum a while back.

https://www.rcgroups.com/forums/show...highlight=rf+4

have a look :-)
Nov 11, 2011, 01:37 AM
Registered User
Nice build, I have the same plan filed away for a conversion one day! Have you added any spars in the wing or is all the strength coming from the paper skin?
Nov 11, 2011, 02:00 AM
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mintie's Avatar
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Quote:
Originally Posted by Gere Sport
Nice build, I have the same plan filed away for a conversion one day! Have you added any spars in the wing or is all the strength coming from the paper skin?
All the strength is in the paper skin... the first layer onto the skin is a 20mm strip that sits on the same place as where the spar would be. There is one top and bottom with the paper gain going length wise.
Then the whole wing is covered top and bottom with over laps on the spar line.
I can now lift the whole plane up just by the wings tips with next to no sag in the wings.
Nov 11, 2011, 02:35 AM
Zen in the art of foam
djacob7's Avatar
Looks like a very neat build.
How will the landing gear be arranged?
Nov 11, 2011, 02:50 PM
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mintie's Avatar
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Thanks for the comments guys.


birdofplay... thanks for that site that is a nice build.....mine is only a park flyer so is just very basic.



djacob7....the main wheel is already mounted as per pics... but non retract... one center wheel and a tail wheel.
At this stage will not mount any wing wheels or wires as I fly in a park and the grass is ofter long so will hand launch and land back in the grass.
Nov 12, 2011, 10:09 PM
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mintie's Avatar
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A bit more done today ... now have the aileron servo mounted,rear wing hold down bolt in and the rear push rods ready to install.
Made up both the motor cowl and canopy foam block molds and now have a bit of sanding to do.
pic included is of a finished full size RF 4.
Nov 18, 2011, 04:00 PM
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mintie's Avatar
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A bit of progress...have been making up the canopy and cowl blue foam blocks and have them roughly in shape.
Just now doing the final prep for the canopy so as to pull a clear one off the mold.
Also making up a vac box to do the pulling,this will be my first attempt so looking forward to that .
Wings now have the sealer coat on and ready for a splash of white paint.
Nov 18, 2011, 11:00 PM
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Bill Smudge's Avatar
Hey Mintie,

Very nice build!! I like your use of all the different materials, great looking craftsmanship also.

Hope she flies great for you..

Regards,

Bill
Nov 20, 2011, 09:18 PM
Registered User
Hey mintie.
Just wondering about the plug that you are making for the canopy. Have you done this method before? And does it stand up to the heat and pressure of the vacuum forming without distorting?
I've been wondering about this method for some time and was just about to test it, but if someone else has done it, I can learn from their success and failure before I go for it.
Your plane is top notch! Love seeing guys using foam and non conventional materials to build beautiful models.scale doesn't belong to the balsa guys only!
Nov 20, 2011, 11:06 PM
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mintie's Avatar
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Thanks for the coments... Bill Smudge and gmwahi....yes I hope it flys nice..That is my plan at this stage.

As far as the canopy goes ..This method does work fine as one of my flying buddies has done very similar to pull his canopies.
Just dont expect to pull a heap of them from this mold. we do it this way for one offs for our own planes.
The method is quite quick to do a plug like this. The plug is blue foam which is a heap denser than white foam will stand a lot more heat and pressure,so makes it good for one off canopies. The paper and glue just add to the robustness


Yes I agree scale can come from all sorts of materials not just balsa.
Nov 21, 2011, 09:17 AM
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Awsome! Looks like I'll be modifying a few planes this week to clear canopies! Just don't have the ambition at the moment to make a bunch of pine plugs, and balsa is just too much money to make one off molds out of.
Nov 22, 2011, 12:15 AM
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mintie's Avatar
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Quote:
Originally Posted by gmwahl
Awsome! Looks like I'll be modifying a few planes this week to clear canopies! Just don't have the ambition at the moment to make a bunch of pine plugs, and balsa is just too much money to make one off molds out of.
Yip give it a go ....I had a chat to my flying buddy and he used white foam and brown paper and it worked fine.

keep us posted on you results. as I will with mine.
Nov 22, 2011, 01:16 AM
Registered User
Thanks mintie! I'm carving a plug right now for a skyraider canopy and will cover it with masking paper. Easier than wood so far by a long shot. Only need it to hold up to a few pulls.
Looking forward to the rest of your build. Take care.
Nov 26, 2011, 12:21 AM
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mintie's Avatar
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Cowl now finished and fitted.
Motor and ESC mounted
Hinging ailerons at present then give them a squirt of paint
Half way through building my vac box so as to build the canopy.
Put it out on the grass today while working on the 140 and took some outside pics.
Last edited by mintie; Nov 26, 2011 at 01:10 AM.


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