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Old Aug 14, 2013, 06:49 AM
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Australia, QLD, Brisbane
Joined Dec 2004
22 Posts
Build Log
F 111 Twin 90mm EDF

I have just taken the first steps in what is going to be my most ambitious project to date, an F 111 that I intend to power with a twin edf setup, probably in the 90mm size. A little background on the project and myself before I begin though.

I have been flying for about 16 years covering almost the full spectrum of aero modelling: Helis, large scale warbirds, ICDF jets, turbines and large scale aerobatics. Recently my interests have shifted over to the build and design side of modelling with a couple of large gliders and a composite electric soarer for the days when a tow plane isn't available.

This project first started around the late 90s when members of the club I belong to now (RAAF Amberley) were approached to repair an old wooden display model of one of the F111 squadrons. The model in question had some damage to it and it was decided that the model could be used as a plug to produce a set of moulds for a composite fuselage withe the wings and tail planes to be foam cores. The decision was also made at this stage to correct a few of the scale deviations when preparing the plug. Fast forward a lot of hard work and the moulds were produced along with the promised replacement display models which left the club in possession of the moulds and not sure what to do with them. A model was made from them and fitted out with an OS 91/Ramtec combo with the intentions of having it taxi around at an airs how before finally getting it ready for flight. Long story short the model was never finished for flight as the wing swing mech may not be up to the job, it is based on a single servo design. Having now seen the finished model it is an impressive thing and I HAD TO HAVE ONE, which is how I have arrived at the point I am at now.

The moulds have been borrowed and I am in the process of waxing them up in preparation for laying up my first fuselage. I am intending to pull a couple of them out of the moulds so I have something to try and fit parts to before getting the flying version ready. Without running a tape measure over it I can't be certain however I believe the model is around 1/12th scale and looking at it I am sure I can a twin 90mm edf power system into it. I am also working on a screw jack built from a modified servo to drive the wings and looking at how I am going to drive the tail plane halves as I am intending taileron control as the primary means of control. There looks to be plenty of space in he fuselage however I need to keep an eye on the weight..

Now for the questions, I really don't have any large edf experience so any assistance or suggestions that people can provide would be greatly appreciated. I am also looking at the wing spar setup and the pivot arrangements however I would consider any assistance that can be provided in this area also. I will try and get a couple of photos of the finished model up to show what it builds into and hopefully I can get the first fuselage out sometime early next week, stay tuned for updates.

Danny
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Old Aug 14, 2013, 06:57 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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be sure to use pva on the molds after you wax (saves wear and tear on the molds ,and you can prime the molds with primer so you wont have any "pin holes" to deal with when you go to paint the model. at 1:12 scale 2x 80mm fans may work.Jet fan 80mm would be nice.do a serch as there is a guy that was making a F-111 on hear ...think i saw it for sale in the classifieds a few days ago ,he had a great wing swing and scale retracts for it .
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Old Aug 14, 2013, 07:01 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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it's a 1:10 scale and on the 2nd pg in the EDf classifieds Dan Savage was building it ,i think there is a thread on it too.
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Old Aug 15, 2013, 08:37 AM
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Australia, QLD, Brisbane
Joined Dec 2004
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I had a look at the model mentioned, looks very nice and the price seems pretty good to me, I am not in the CONUSA so I will have to keep going with mine. I have the moulds waxed and pva'd now so I will be looking to lay some glass over the weekend. I will be priming the moulds before I lay the parts up to as per the suggestion above, pinholes caused me headaches on a previous build.

As waxing and a bit of pva aren't all that exciting to look at I still don't have any pictures, hopefully this weekend once something worthwhile looking at starts to appear.

I have also done some research on fans, still looking at weights and I think I will be looking at 90mm fans running 8s per side. I have been looking at the extreme alloy fans running the wemotec 11 blade fan, does anyone have any experience with these fans?
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Old Aug 15, 2013, 09:07 AM
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Brisbane, Australia
Joined Oct 2004
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Hey Mate,

Your probably better off going with the new wemo EVO rotor. slightly more efficient than the older wemo rotor, but a heaps better sound.

I have the older style wemo 90mm rotor in my f-86 and have a high blade count ChangeSun fan ( somewhat similar blade count as the EVO) in my Hawk and the sound that comes out of the model are chalk and cheese!

Are these the molds that Mark had in his workshop for years?

Thanks

dave
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Old Aug 15, 2013, 07:42 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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may i suggest a layer of 2 oz. cloth followed by a layer of 3.6 oz. plain weave cloth .thats what i use in my F-20 and seems light and strong enough.i use a bit of 3.5 oz C/F in the nose gear area ....the price of C/F is through the roof right now so i may just use another layer of 3.6 oz glass instead of C/F .
still think 2x 90mm might be too heavy .you need to look at you inlet FSA ,the 80mm might do better. the evo rotor is being used at 80mm by a few guys out there .im sure mark at extreme can fill you needs for fans
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Old Aug 17, 2013, 01:29 AM
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United States, CT
Joined Jan 2013
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Sounds like a great project, Danny!

I think that you should be able to fit 90mm fans into a 1:12 scale 111. I'm working on a 1:16 scale EF-111A, and the shrouds for the 64mm fans I'm using are actually 72mm in diameter At 1:12 scale, this is 96 mm. I end up having one degree of down thrust with my EDF units as high as they can go. There is plenty more room if you are willing to move the engines down, but you would need to make an S-shaped exhaust duct instead of a simple thrust tube, or end up with more down thrust. You might also want to take a look at your wing incidence since this probably factors into how much (if any) down thrust you want.
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Old Aug 17, 2013, 01:56 AM
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As Air Sally pointed out, the FSA is an issue for a 90mm fan if you make scale inlets. I'm at 85% with a 64mm fan so you'd be below this with a 90 mm fan. Weight is also an issue. The actual jet had a wing loading similar to an F-104.
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Old Aug 17, 2013, 05:20 AM
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Australia, QLD, Brisbane
Joined Dec 2004
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Thanks for the input guys, as I have said this is new ground for me so I need all the guidance I can get. I am looking at the inlets at the moment and I for a 90mm fan I would need around 4300mm2 to be at 85% FSA. I have not really looked at the fuselage yet and I find it a bit hard to visualise properly when looking at moulds.

I have also looked at weights and as Air Sally has pointed out, twin 90 mm fans might be too heavy. I will wait until I have the fuselage out of the mould before I start even trying to guess weights. I have the wing templates made and there really isn't a lot wing there.

Glass parts are currently curing in the moulds, should be right to trim soon. Once they are trimmed I will seam the fuse and hopefully tomorrow afternoon, a baby pig will be born.
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Old Aug 17, 2013, 04:21 PM
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Quote:
Originally Posted by spektre57 View Post
I find it a bit hard to visualise properly when looking at moulds.
I likewise find it hard to visualize the molds looking at the fuselage. I'd love it if you could post some pictures of your molds.
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Old Aug 18, 2013, 03:40 AM
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Australia, QLD, Brisbane
Joined Dec 2004
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A baby Pig is born!!!

This update will be short however I wanted to get a couple of pictures up to show exactly what it is that I am talking about. The first pic is first fuselage that I have pulled from the fuselage, expertly held and displayed by my apprentice. The overall length is just over 1800mm from the back edge of the fuse to the nose, as you can see I still have the exhaust cones to mould.
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The next pic is the moulds that the fuselage come from, not shown are the exhaust cones, main and canopy hatch. I will be waxing these up in preparation for the next one over the next few days.
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Next up is a shot looking forward at the intakes, the radius of these is 95mm so I can now work out what FSA I can cover with this.
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Lastly I have a pic of the first model taken from the mould and built for the airshow celebrating 30 years of RAAF F 111. This has an OS 91/Ramtec and has never flown. Certainly looks the part though.
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Old Aug 18, 2013, 03:42 AM
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After reading about your ambitious project I think you are going to build a nice static model. 12th size is much too small for such a complex model as F-111. It will become a "steel reinforced flying concrete block" as far as I'm concerned. If you said 5th - 4th scale you might succeed. If you build it from foam, maybe, but composite, twin 80-90mm, 8S set up, folding wings, assuming retracts as well in such small size, forget it! I hope you will have it ready for static display at our up coming Coffs Coast EDF Jet Meet in March, if not bring down something else. Tomorrow I'm topdressing our strip with 12m3 and 100kg of fertilizer to make it better for boys with their toys, Joe.
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Old Aug 18, 2013, 05:33 AM
Chris
bundaberg
Joined Jun 2004
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Joe so many times you tell others if they don't have anything positive to say , don't bother to contribute to your threads ! Why not then show the same respect to others? spektre57 , keep going with this project, there are many of us who would really like to see this succeed.
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Old Aug 18, 2013, 06:52 AM
Do it Right, the first time!
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United States, MN, Hermantown
Joined Dec 2008
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This was originally intended for the poll thread ( large EDF's) in the Jet Talk forum, but it will work here. He is quite the I man, it's ALL about him. If your plane isn't the size of a semi truck , it ain't big enough.

Very SAD!
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Old Aug 18, 2013, 07:15 AM
Da' Cajun
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Lake Charles, Louisiana
Joined Jun 2009
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Quote:
Originally Posted by thespit View Post
Joe so many times you tell others if they don't have anything positive to say , don't bother to contribute to your threads ! Why not then show the same respect to others? spektre57 , keep going with this project, there are many of us who would really like to see this succeed.
↑ this

...I doubt though, that personalities so boorish will see their own hypocrisy and dial it back.


Fantastic project!!! - BTW
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