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Old Sep 01, 2012, 09:00 PM
Firecracker!
BillO's Avatar
San Francisco & Santa Cruz
Joined Oct 2004
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Hey Joe, I plan to get a video for sure.

I do appreciate your comments Walt and I respect your experience. I have no EDF experience. If this plane gets over 3 lbs (> 48 oz), I agree that a bungee is in order. If it is 2 lbs and change, like 36 oz, what do you think?
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Old Sep 01, 2012, 09:14 PM
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Crystal River Fl.
Joined Jul 2008
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I've got a 70mm mirage that is 24oz? Without the battery, About 36 oz rtf, it launches pretty good, but you still have to be careful with this one even though it has a large wing area... I wouldn't want to go any more really... Is there any of your flying buddies at the field flying EDF's that you could talk to? You could build this one light as you can and try it, if it works out good then do the finish work on it. I always maiden my planes before doing any finish work on them, you may have to do some adjustments to them then do finish... There is not much doubt that a bungee launcher is safer than a hand launch, but they are something else to carry around and set up... Seems everything has its pros and cons... w
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Old Sep 01, 2012, 09:50 PM
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United States, WA, Vancouver
Joined Mar 2012
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hey Bill,

if landing rash is all you are worried about, instead of glass just spritz the bottom with 3M-77 then put long strips of packing tape on, its nice and slick and actually holds up well for belly landing, and is easily replaceable when it starts showing wear. I have foam rails that I glued on for both landing on and a nice handhold for launching
on a side note I just tried a 3S 1600mah 20C pack in the Phantom, with it almost to the bulkhead under the front of the canopy it makes CG, and it scoots her across the garage floor real well, I am gonna try flying with it and see what happens.

Joe
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Old Sep 02, 2012, 05:09 AM
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Hey guys this is all good stuff to keep in mind. Joe your comment about the ducting... Never worry there she has a sharp split inside. although it added a bit of weight and was completely acidental. When I removed the foam the drywall compound stayed in and was very difficult to remove so I shaped it instead. I haven't had a chance to get thrust measurements but will try later tonight. I have to spend time with the wee lad today so all model related stuff gets put off.

What I can say is that the thing wants to take off under half throttle from a 3s 2300 mah lipo. It also feels like a lot more thrust from when I had just the fan alone. I took measurements from my 70mm F18 when I made the duct. I just hope it works.
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Old Sep 03, 2012, 11:12 PM
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good deal Shane, keep us posted, if it "feels" like it wants to fly it probably will

Joe
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Old Sep 04, 2012, 01:59 PM
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Crystal River Fl.
Joined Jul 2008
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Hey Bill,,,, have you started this one yet?? w.
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Old Sep 04, 2012, 05:45 PM
Firecracker!
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San Francisco & Santa Cruz
Joined Oct 2004
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Hi Walt, I just got my fan in the mail -- it looks like a piece of sculpture! Now I can get the ducts drawn up and built. I wanted to do that before putting any of the other parts together so I can see how everything will fit. I'm thinking the intakes will be a bit narrower than on the plans to get them down to 100% FSA.

I'm learning Sketchup on this project, so things may not go along quite as fast as I would like. 3D is quite a bit more challenging than 2D!

I should be able to get some advice from guys at the club, but there is not all that much EDF activity there. I've only been to 1 meeting so far.

Shane, I would really like to see how your exhaust duct works out. Mine is probably going to look fairly similar.

Thanks for the tip about tape on the bottom of the plane Joe. I'm thinking I will launch underhand, kind of like throwing a bowling ball. I've read that this is more reliable and safer than throwing overhand. I will probably also get a cheap foam ARF to practice with first too. Something like the Phase 3 F-16.

As for my reasons for glassing, they come from my experience with flying both foam and composite slope gliders. The first is all around durability for transport/storage and flying. Bare blue foam is very fragile, easily dented, scratched, and gouged. Glass will also make the airframe stiffer, stronger, and cleaner aerodynamically, so the plane will be more responsive and faster with the same amount of power. I will also be able to have sharp trailing edges on the flying surfaces, which will reduce drag. Improved appearance is the last, though minor, advantage.
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Old Sep 04, 2012, 06:20 PM
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Crystal River Fl.
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Nice looking fan Bill. The phase III ef16 is the best buy out there for an EDF. It flies better than anything I have seen, a very wide speed envelope, cheap and a lot of fun! You might check hobbypeople.net, they have had it on sale lately for 79.95! Get the ef16 I'd get a 30c battery, and fly fly fly, have fun and learn how am EDF is different, but I have to warn you, the ed16 is not typical of most EDF's,, it flies much easier... W
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Old Sep 04, 2012, 06:41 PM
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Bill that is some fan! Sexy weeeeoooooo. I bet that thin gis going to have some sound. Walt I am not questioning the F16 because I'ce never flown it but to my thinking it just looks twitchy. It's a sight cheaper than my 70mm F18 from starmax but I have to say that the aditional cost for stability of flight is well worth it.

I've set aside the F4 for the moment (yet again) due to the horizontal stab. I want it all moving and have yet to come up with a reliable solution. I've also got to get that thrust test done as well now that the ducting is in. Hmmmm. I've seen the way the kerosene jet jocky's have done it and I might copy them. Could be a week or so. Till then keep em coming
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Old Sep 05, 2012, 10:52 AM
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Bill I did a rough measurement of thrust on a set of scales. It is by no means conclusive as all I did was hold the model nose down on the scale and hit the accelerator. I'm unsure if this is good results as I am new to EDF but I got 18-21oz of thrust over 20 seconds. This looks like 1lbs 2oz of thrust. Using 3s 2300 lipo. At the moment with out the wing the model is weighing in at 1 lbs.
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Old Sep 05, 2012, 02:39 PM
Firecracker!
BillO's Avatar
San Francisco & Santa Cruz
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Hmm, well that is a data point at least. Are you going to fly on 3s or 4s? Sounds like it might be a bit underpowered on 3s.
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Old Sep 06, 2012, 03:48 AM
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United States, WA, Vancouver
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Holly Christmas Bill!
nice fan unit! that otta make it giddy up and go.

here are some pics of one of my slope ships from a few years back, my SU-27 I cut from epp foam, strapping tape for reinforcement and covered with white UltraCoat then painted, dont ask what it weighed...I dont remember ever weighing it but it was fairly heavy and liked higher winds to fly in, anything over 25mph and it flew great, 30mph and up was a blast! the neat part was the thing bounced like a rubber ball on bad landings with no worries about hurting it

Joe
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Old Sep 11, 2012, 04:43 AM
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Lovely looking model There Joe. That's something I've wanted to try but can't get my head around. Slope soaring. Bill I will see what I get from a 4 cell tonight. What about your setup?
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Old Sep 12, 2012, 08:24 PM
Firecracker!
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San Francisco & Santa Cruz
Joined Oct 2004
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Joe, that is an awesome sloper -- you've really got some skills!

Shane, my setup is supposed to produce 52 oz of thrust on 4S. I'm hoping to lose no more than 20% with all the ducting, so I'm thinking around 42 oz installed. If I can keep the weight under 42 oz I'll be a happy camper.

On that front, I glassed the fin and stab. Based on that, I'm thinking glass will add about 6 oz to the AUW. The next big thing in my mind is how much will ducts weigh. I'm going to make the exhaust duct next...
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Old Sep 18, 2012, 01:08 AM
Firecracker!
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San Francisco & Santa Cruz
Joined Oct 2004
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Here are couple of diagrams of my duct design. The intakes are 100% FSA and the exhaust is 85%. I may move the side walls in 5 mm (width of 1 sheet of foam) to fit the intakes a little closer.

Hard as I tried, I couldn't straighten out the Sketchup side view of the exhaust, so I may just do that on the build. First up is the exhaust duct.

One question though: how do you connect the ducts and the fan shroud together? I'm thinking to just tape them together. Let me know if this is a bad idea...
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