|Nov 10, 2006, 10:58 PM|
Next Build? - Peter Rake 54" SE5
Oh no - not another SE5 you say The SE5 is probably almost overdone but after the success of my 36" version by Peter, and my subsequent selling of it to a friend, I invested a part of the proceedings in another, bigger SE5 to help me through my rather rocky road to flying a larger, faster more powerful model. I feel almost guilty starting another model while I have two unfinished (Hawker Demon and Bleriot XI) but both of those models have aspects which need more head-scratching and I'm still thinking about the way ahead with them. I also have two models which need maidens or successful first flights (Duigan and Ryans Daughter) plus an ever growing list of desirables for which I have plans - Walrus, Ant-6/TB3, Nijhuis Lancaster etc...........
So in the interim, I decided on a model that I know will fly, is not an own-design or conversion and is reasonably simple.
This SE5 is also deceptively large
At 54" span, it should weigh around 4 lbs, has about 7.5 sq feet of wing area and is over 18" high!
With Brian Allen doing a close-to-scale version, and Ian Easton having built and flown a hand-cut prototype of the Rake design, I thought another build may be superfluous, but I dont believe anyone has described a build of the Manzano Laser short kit. Correct me if I'm mistaken.
To start things rolling (but not too quickly) here is a photo of the bits from Charlie (or most likely - Vicki!). 16 sheets of balsa in various thicknesses, two sheets of ply part, plus a bag full of other heavy ply bits - looks formidable!
The good news is that the construction is almost identical to the 36" machine so it should present few problems. (at this stage anyway).
Now for some serious thinking about versions, modifications, detail level etc....... this is the largest/heaviest model I've built
|Nov 10, 2006, 11:30 PM|
Among the things I am thinking about are:
Level of detail - I love detailing models but at this scale (1/6), the possibilities are almost endless. Do it the same as my 36" version?
Choice of prototype aircraft - good to decide now as some construction will depend on the variant chosen
Various construction options - where and if to slightly modify Peter's design to suit the points above, covering options (Solartex too heavy, Litespan too light), motor and battery choice and mounting methods.
My initial thoughts are to do a version with the rounded radiator as per Peter's design - the Hispano-Suiza ungeared engine, 4 blade prop - early SE5a models, simple undercarriage fairings - early SE5/5a.............
Lots of research needed
I may have to talk nicely to Vintage1 to get a design for a 4 blade wooden prop - even if only for static - the original is 7' 9" diameter = 93" @1/6 scale = 15.5" - I'd need about a 500Kv motor to turn that!
My 870 Kv outunner will turn a 12-13" prop, but like Ian Easton's model, it may have to shrink for flying. Hmmm......
|Nov 11, 2006, 12:15 AM|
Detailing in this size can be a lot of work, but it is well worth the effort. As for how much, just keep going until you can't stand it any longer Remember, you never finish a scale model, you just stop working on it.
I think the most important thing is not to be in a hurry to finish and fly it. Treat it as fine wine, let it age and gather subtleties before serving. (Maybe I need to have a glass of the real stuff!)
|Nov 11, 2006, 01:37 AM|
For anyone interested (hint..hint), here is a photo of an SE5a 4 blade prop.
|Nov 11, 2006, 05:10 AM|
Ok ok.....bit of a hiatus here while Charlie cuts MY next model..I'll have a look at that prop this weekend if I can escape the gardening..
I would have thought you could bring the model in at not much more than 3lb to be frank..
RPM on a 15" prop? somewhere around 2500-3200..on 2s LIPO around 500 KV then..yup.
Nothing suitable in the AXI range then. Not without a gearbox.
MPJET 2820/10 is ALMOST there..14" prop possible on 2s LIPO.
Hacker A30 12XL..well it would be a rocket ship, but it would survive WOT..
Nope. Motocalc lists no brushless motors below 10oz and below 600KV.
And I can't find one elsewhere either.
Now you know why I have a load of modelairtech belt drives and astro cobalt 15's in my drawer..
Pat: Very happy to do a prop, but you will have to settle on a power plant first.
It looks like Tom Hunt is not doing belt drives any more - they have gone from his web site. Arrggh.
Oh well. best recommendation then might be the AXI 2820/12 with the new AXI planetary 3:1 gearbox. That gets us to 2700 RPM and a 15x15 prop on 3s LIPO at 20A nicely. Or a 2820/10 if it turns out 'porky'.
|Nov 11, 2006, 06:20 AM|
Vintage - I know you hate the idea but I'd be happy with a pattern for a dummy prop - I'd like to tart it up with brass bits etc so it has to be the right size and pitch (whatever that is on this machine). My motor is an E-Flite 25, which the spec sheet says up to 14X7 on 3S. 40 amp max.
I'll use and 11 or 12 X 8 or so for flying.
Maybe you already have a 4 blade plan I can resize to make a dummy?
I agree on the weight - Ian Easton got about 4lb with a 600race plus belt drive and Nicads. So 3lb should be possible.
No panic about the prop - way down the track.
|Nov 11, 2006, 06:33 AM|
That gearbox doesn't go on the 28xx motors, it's for the 22xx series.
Personally I think the 2217/16 or 2217/20 geared 3:1 would do it with a scale-ish prop at 3lb. They are really 180 watt input motors but you get good efficiency so more of that input power converts to output than it would with a Speed 600. And with a suitably big coarse prop you can get a lot of tractive effort and pitch speed for your watt.
But you will need noseweight so an Astro Cobalt geared would be a very good safe choice, if you wanted to run a more conventional model-type prop for flight.
According to the vintage prop website it's 93"x121" so scale is about 15.5"x20".
|Nov 11, 2006, 08:29 AM|
I think a 15x15 would do for flying as well as dummy, if we cold get down sub 3K RPM.
I am sure a 2212 geared would fly it too.
Anyway the FE8 11x11 is the same sort of prop..that would fly it AND look good. AXI 2820/12 on 2s LIPO.
To go to 15.5x 20 would be a very slow RPM prop.
I make it about 2500 RPM to fly a 3 1/2lb biggish model About 180W.
Mmm. AXI 2212/26 on 3s LIPO and 3:1 gears looks about right. Not overly burdened with power, but enough. 2000 RPM flat out
What we need is a belt drive beween 3:1 and 6:1 ...to really get these props whirring in scale fashion.I've been looking in to that already..
Oh. I had forgotten the 2212/17. Ideal mate! With gears..
|Nov 11, 2006, 08:59 AM|
This is going to be a great thread to watch! Just remember that details can be added after you have flown it, so this can be a lifelong event! I kinda felt the same way with the SPAD, being my largest plane. Still like it. Don't use Solartex!
I am partial to gearboxes and belt drives, which is what I put in the SPAD, but, even at 2.33:1 I still have over 5000 rpm on the prop. There are a couple of folks making gearboxes for the bigger motors these days.
I looked at a scale prop for the SPAD, it would have been near 17", and had about 1.2" of ground clearance I settled on a 14" to let it clear the grass I normally fly from.
|Nov 11, 2006, 10:15 AM|
Oh, here's an interesting motor.
suitable they say for an 18x10 prop on 3s LIPO at about 3300 RPM. 150Watts.
Specs don't seem to agree on what it actually is, though. Motocalc reckons nearer 32A to swing an 18x10 at 3300 RPM on 23s LIPO. Megamotorusa says 20A.....more like 200W than the quuted 150W.
I make it 3000RPM on a 15x15 4 blader on 2sLIPO. Same weight as a speed 600 roughly. About 40A..
Price is not unreasonable either. Not cheap, but mega is mega!
|Nov 11, 2006, 02:57 PM|
Talking about Scale
With all this discussion on motor/GB selection, I am still going to build the model for my E-Flite 25 - perhaps a bit powerful for this model but can be propped down for flight. The SE5 front-end can accommodate almost anything - Pete uses a flate plate to mount the 600/belt drive but this can be changed at any time - as I did with the 36" SE5.
I need to discuss 'scale' on this forum as few of my club friends even know what I'm talking about - faster is better is the norm and about the only consideration.
Thinking about what makes a model look scale = what makes it look real. On the ground, obviously size and proportion is the most important - and - staight-forward part. Straight linear or cubic scaling, but in the air?
As I understand, the intent should be to fly the model at a speed which makes it look the same as the real thing - this would be a simple linear scale. A 100mph WW1 fighter at 1000' should look like a 1/10 scale model at 100' doing 10mph. I guess this is a major problem for smaller scale - aerodynamics and physics is not scaled and most models would have trouble flying that slowly (safely) so we have to have much higher than scale speeds.
Is my thinking correct? So achieving good low-speed characteristics should be a requirement for small scale model (1/4 scale people dont have such a problem). Even a small 1/10 warbird at, say 50 mph would be doing 500mph scale!
Just trying to sort things out in my head - I was thinking about prop pitch, pitch speed and stall speed etc in relation to scale props
Enough raving on (sorry) - today is a flying day and it is reasonably calm but the ground is very wet after a shower so the Duigan is out.......
|Nov 11, 2006, 03:41 PM|
pmisuinas, I just checked on the Astrofight - seems the motor that was about the right power still came out over 750 Kv with GB. The bigger 25 model came closer but would probably be too powerful (and pricey). Worth a look though With a 15" prop, the options seem very limited. A static and seperate flying prop maybe the easy answer.
On the prototype, Ian Easton used a 12X6 / speed 600 / 2.3:1 on 8 cells - prop looks tiny but it flies!
|Nov 11, 2006, 05:07 PM|
Ok, drawngs done for 15.5x15 4 blader, with Charlie now.
Pat: there is no correct 'scale speed' because gravity and air density don't scale...
There are two scale speeds - 'rate of appraich' which is full size odel divided by te scale. Its iompossibly low for most models.
The second is 'aerodynamic scale' which is the square root of the scale factor. The model flies at the right angles and diametyers and so on with this, but looks 'fast' in the air.
If you use a high speed video and slow it down by the square root of the scale, THEN it looks PERFECT.
The best compromise is somwehere between the two, which is realistically as slow as you can manage actually. The model will need extra power to be 'flown' round loops its momentum should carry it round, and may need to be banked steeper and flown in larger circles than it wants to. With a touch of opposite rudder to keep the nose up..
The props WIP and I have been working on work more or less with the aerodymanic scale, though they are linear scale reductions. No I haven't totally got my head round it either.
If you want to fly with an 11x11 use the FE8 4 blader..that you will need to drive arounnd 4500 RPM.
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