Futura57 Posted August 25, 2023 Share Posted August 25, 2023 I have done some searching but cannot find what I'm looking for. By all means send me a link to an existing thread if it answers my questions... I have recently purchased a 50mm FMS 11 bladed EDF unit for 4S power with a view to designing an EDF version of my own design Top Quark aircraft. I have never owned or flown an EDF model before. I'm comfortable with inlet and outlet duct requirements, but I want to ensure the EDF unit can be easily removed and replaced in the event of a burnout or other unforeseen problem. The FMS EDF unit does not have any moulded mounting lugs on the outside of the casing. I'm not sure how well the plastic will take to epoxying some ply or carbon lugs or how well it will stand up to vibration or cause distortion of the circular casing. I see from some TN designs that the EDF units are tack glued at their bell inlet flange (I like that word 🙂 ) to a two part 6mm lite ply former, which can separate and slide out via a sealed hatch in the fuselage. I also note that TN generally pushes the thrust tube in through the back end of the fuselage during construction, tapes the join and hot glues it to at least the last fuselage former. What I'm not sure about is whether the thrust tube should also be glued to the back end of the EDF unit or just a tight fit. For easy removal I would prefer it if no glue was required anywhere, so I'm unsure what to do. Also, should the inlet bell flange (there's that word again) be sealed in some way around its mounting former? What else should be sealed air tight in a EDF installation? Any steer on the above would be most appreciated. Quote Link to comment Share on other sites More sharing options...
John Lee Posted August 25, 2023 Share Posted August 25, 2023 I built TN's Gnat & followed his instructions - a couple of blobs of hot glue to secure the fan to the former & a couple of short bits of Scotch tape to attach the thrust tube to the fan unit. I was somewhat sceptical but it all works 100% in practice. No other sealing or fixing. I've had to remove the fan once and it was easy to unpick the glue blobs. A heat gun could be used to soften the joints but I did not find it necessary. 1 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted August 28, 2023 Share Posted August 28, 2023 Futura57 In my experience replacing the EDF is less likely than having to repair the plane.😉 On this basis I concentrate on gluing the EDF in securely rather than worry about getting it out. I have several own design planes (including a Gnat a touch bigger than TN's) with 50 mm EDFs. None of the EDFs have failed but crash repairs rather more so. Quote Link to comment Share on other sites More sharing options...
john davidson 1 Posted August 28, 2023 Share Posted August 28, 2023 Hot glue does not penetrate balsa so can be removed by snipe nosed pliers,with a twisting action usually The first use of hot glue I saw was years ago in wood lathe work, attaching work pieces to the faceplate, the piece could then be detached when wanted, (no screwholes) REALLY hot sticks better to the plastic shroud Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted August 30, 2023 Share Posted August 30, 2023 Hot glue also softens and can be peeled off after applying iospropyl alchohol (IPA) , providing of course that the item can tolerate IPA. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted August 30, 2023 Share Posted August 30, 2023 Having owned and build a few EDF powered models I would note that you should not underestimate the suction that these things can generate. I have had it slowly pull servo cables out of the fuz into the inlet track, see someone else's edf suck unrestrained servo wires right through the fan and take all the blades off on a test run! My FT model can be seen to distort (implode) the fuz when the fan is on full tilt. Clearly more cheat holes are required! As above, just sit the fan housing on some yokes with a dob of hot glue and you should be ok Quote Link to comment Share on other sites More sharing options...
john davidson 1 Posted August 30, 2023 Share Posted August 30, 2023 And align it very carefully parallel with the fuselage datum Quote Link to comment Share on other sites More sharing options...
Futura57 Posted September 1, 2023 Author Share Posted September 1, 2023 I have to say I'm somewhat underwhelmed. Not so much by the few responses, but by the apparent low-tech approach to mounting EDF units. Not even opinions on why some EDF units have mounting lugs and some don't. Which is better, given that thrust-line alignment seems to be important.? Hey ho, Occam's Razor and all that 🤔 I've a while before confronting the issue so will continue to ponder and invite any further comments. Thanks. Quote Link to comment Share on other sites More sharing options...
Lipo Man Posted September 1, 2023 Share Posted September 1, 2023 8 minutes ago, Futura57 said: I have to say I'm somewhat underwhelmed. Not so much by the few responses, but by the apparent low-tech approach to mounting EDF units. Not even opinions on why some EDF units have mounting lugs and some don't. Which is better, given that thrust-line alignment seems to be important.? Hey ho, Occam's Razor and all that 🤔 I've a while before confronting the issue so will continue to ponder and invite any further comments. Thanks. I suspect you may be overthinking it - perhaps it really is fairly simple. My own design EDF plane (64mm fan) has the fan pushed into two foam sheet formers and held with a blob of hot glue. It’s got several hours cumulative flying time so far with no issues. Maybe the answer to why some have lugs and some don’t is that it doesn’t really matter either way? Quote Link to comment Share on other sites More sharing options...
PeterF Posted September 1, 2023 Share Posted September 1, 2023 I have used various techniques, blob of bathroom silicone sealant to hold fans into foam where there was no mounting lugs, having my son who has a laser cutting business make up some mounts for fans without lugs, screwing the fan lip to a bulkhead per a Chris Golds plan, and using lugs. All work OK. Quote Link to comment Share on other sites More sharing options...
PeterF Posted September 1, 2023 Share Posted September 1, 2023 Better image of the Fans screwed to the bulkhead from the Chris Golds Sperrin build. Too late to edit the original post. Quote Link to comment Share on other sites More sharing options...
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