.20 size taurus
05-04-2011, 03:12 AM
#4
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RE: .20 size taurus
You Taurus looks nice. It's funny how the Taurus lends itself well to a 50 inch span model.
I too made mine 50 inches and I know of others.
You'll like the way it flies.
Paul
I too made mine 50 inches and I know of others.
You'll like the way it flies.
Paul
05-05-2011, 03:53 PM
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RE: .20 size taurus
I fly at Prado, whitter and santa fe, once in a while I make it over to the baisn. Where do you fly?It would be nice to Fly with other people interested in classic pattern.There are not too many people around here( that I know interested in older stuff) Rob
05-07-2011, 04:54 PM
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RE: .20 size taurus
Hi guys,Here is where I am at. Still need to sheet the bottom of the wing,add the leading edge and wing tips,then a realy good sanding.I have picked the stock I will use for my ailerons. Thanks for looking Rob
.......i assume you used dope?
05-28-2011, 03:22 PM
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RE: .20 size taurus
Rob,
beautiful job!
500 squares is a pretty big wing for a 25 sized model but then again, in those days models were large for the power available. A 25 FSR ought to fly it in a very vintage like manner. I'd imagine a 46-48" wing with something closer to 440-460 squares would produce a more performing model with an FSR. An OS 32F might be a nice alternative if you find it lacking in power - about 1/5 more power available.
David.
beautiful job!
500 squares is a pretty big wing for a 25 sized model but then again, in those days models were large for the power available. A 25 FSR ought to fly it in a very vintage like manner. I'd imagine a 46-48" wing with something closer to 440-460 squares would produce a more performing model with an FSR. An OS 32F might be a nice alternative if you find it lacking in power - about 1/5 more power available.
David.
05-29-2011, 07:33 AM
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RE: .20 size taurus
Rob,
for some reason the FSR engines are not on this list:
http://www.osengines.com/engines/eng...continued.html
but I would imagine the 25 and the 28 to be pretty similar in performance. On the same prop, the 28 might turn 500 rpm more than the 25 or something in that range. A 32 changes things as you can turn larger props. 25-28's typically turn 9x6's while with 32's you can turn 9x7's or 10x6's as a sport 40 might. Also, 32's are about 1.0 - 1.2 bhp spec while 25-28's are 0.7-0.8 bhp.
Think of sub 30 size engines delivering about 600-650W (SI units) while 32-35 size engines delivering about 750-800 W. That's a significant difference as is the prop.
With that said, I would take the two FSR's on to a test stand, tach them and choose the one you prefer. The 28 might be the logical choice. If you find the plane lacking in performance (although it sounds reasonably light at 56 oz), you can always source a 32F or a 32 SX. The SX has about 1.2 bhp - they are strong on 10x6's and can fly a 4 lb model happily.
BTW, I discovered yesterday that a classic 32F is a couple of ounces lighter than a modern 25 AX (11 oz vs 9 oz)!
David.
for some reason the FSR engines are not on this list:
http://www.osengines.com/engines/eng...continued.html
but I would imagine the 25 and the 28 to be pretty similar in performance. On the same prop, the 28 might turn 500 rpm more than the 25 or something in that range. A 32 changes things as you can turn larger props. 25-28's typically turn 9x6's while with 32's you can turn 9x7's or 10x6's as a sport 40 might. Also, 32's are about 1.0 - 1.2 bhp spec while 25-28's are 0.7-0.8 bhp.
Think of sub 30 size engines delivering about 600-650W (SI units) while 32-35 size engines delivering about 750-800 W. That's a significant difference as is the prop.
With that said, I would take the two FSR's on to a test stand, tach them and choose the one you prefer. The 28 might be the logical choice. If you find the plane lacking in performance (although it sounds reasonably light at 56 oz), you can always source a 32F or a 32 SX. The SX has about 1.2 bhp - they are strong on 10x6's and can fly a 4 lb model happily.
BTW, I discovered yesterday that a classic 32F is a couple of ounces lighter than a modern 25 AX (11 oz vs 9 oz)!
David.
05-29-2011, 07:35 AM
#19
RE: .20 size taurus
ORIGINAL: doxilia
Rob,
beautiful job!
500 squares is a pretty big wing for a 25 sized model but then again, in those days models were large for the power available. A 25 FSR ought to fly it in a very vintage like manner. I'd imagine a 46-48'' wing with something closer to 440-460 squares would produce a more performing model with an FSR. An OS 32F might be a nice alternative if you find it lacking in power - about 1/5 more power available.
David.
Rob,
beautiful job!
500 squares is a pretty big wing for a 25 sized model but then again, in those days models were large for the power available. A 25 FSR ought to fly it in a very vintage like manner. I'd imagine a 46-48'' wing with something closer to 440-460 squares would produce a more performing model with an FSR. An OS 32F might be a nice alternative if you find it lacking in power - about 1/5 more power available.
David.
05-29-2011, 08:37 AM
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RE: .20 size taurus
I measured 460"sq so its a little less than I estimated. all up weight is just under 4 lbs, with fuel maybe just over. I am shopping for a OS .32 but I will test fly it with the .28 for now.
05-29-2011, 08:57 AM
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RE: .20 size taurus
ORIGINAL: UStik
Yes, it's really beautiful! But, David, scaling the original Taurus down to 50'' wingspan should give only 370 sqin wing area and then 3.75 lbs weight would make for 23 oz/sqft wing loading. That's as much as the Kwik-Fli Mk III in the background has and noticeably more than the original's 18. That alone makes this model not that vintage-like. The 25 FSR as a Schnürle ported engine could give even 2.4 lbs static thrust (with a 9x6) resulting in 0.64 thrust/weight ratio. That's really OK (Kaz had his throttled to about 0.675 for contest), you just might find the .28 or even a .32 more ''interesting'' (but adding to the weight).
Yes, it's really beautiful! But, David, scaling the original Taurus down to 50'' wingspan should give only 370 sqin wing area and then 3.75 lbs weight would make for 23 oz/sqft wing loading. That's as much as the Kwik-Fli Mk III in the background has and noticeably more than the original's 18. That alone makes this model not that vintage-like. The 25 FSR as a Schnürle ported engine could give even 2.4 lbs static thrust (with a 9x6) resulting in 0.64 thrust/weight ratio. That's really OK (Kaz had his throttled to about 0.675 for contest), you just might find the .28 or even a .32 more ''interesting'' (but adding to the weight).
However, Rob's model weighs 60 oz (not the 56 I mentioned above - I thought he said 3.5 lbs) at 52". A 46-48" model ought to way correspondingly less - maybe 50-56 oz. The wing loading ought to track provided the smaller models are built adequately light.
I do think that the 25 or 28 FSR will be fine though just not as interesting as a 32 as you mention. I was just trying to point out that the 25-28's are more similar to each other than the 28 is to the 32's. The 32 SX is in particular quite a bit more engine than the various 25's - not that one is needed - it just might be fun. I think I would plan for a 32F on a 52" pre-80's classic. 25's for 48" or under.
Just my perspective.
David.
05-29-2011, 08:59 AM
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RE: .20 size taurus
ORIGINAL: HVACMAN
I measured 460''sq so its a little less than I estimated. all up weight is just under 4 lbs, with fuel maybe just over. I am shopping for a OS .32 but I will test fly it with the .28 for now.
I measured 460''sq so its a little less than I estimated. all up weight is just under 4 lbs, with fuel maybe just over. I am shopping for a OS .32 but I will test fly it with the .28 for now.
that actually sounds more like it. A 48" model would have somewhere close to 400 - I'd guess close to 420 actually. But that doesn't matter.
The 28 will be nice. If you find a 32F, they are ABC engines and their carbs don't have the remote needle valve of the 32 SX - a bit of a nuisance in my opinion but good in glass cowled models.
David.
05-29-2011, 09:15 AM
#23
RE: .20 size taurus
I don't object, just wanted to make clear that an old (even better: really old) .25 would be fine but the high wing loading gives a different character of the model, anyway. If I see it correctly, the 460 sqin are wing and stab for 50" wingspan. (At least that's what my spreadsheet says.) The specified wing loadings were for the wing alone. Rob said 3.75 lbs giving 23.5 oz/sqft, now 3.95 lbs give even 24.6 oz/sqft. That's typical for the late 1960s and would make a matching 0.8 thrust/weight ratio advisable, so a .30 but a vintage one. If you take a modern engine better take a 25 or such for weight saving. (Not to spend most of the added thrust on the added engine weight.)
05-29-2011, 09:50 AM
#24
RE: .20 size taurus
Just tried in the simulator: The 24.6 oz/sqft fly quite well, the model is just as fast as the Kwik-Fli, even though not as smooth. It spins and snaps like crazy (due to the wingloading), but still not vicious. The .25 giving .6 thrust/weight is well enough for pattern. Should be fine! (As a side note: Phil Kraft found a .20 enough for his 0.66 scaled Flea-Fli, so a .25 should be right for the .71 scaled Taurus with the cambered airfoil, even at this high wing loading.)
05-29-2011, 11:09 AM
#25
RE: .20 size taurus
450 squares worked great for a OS 25 FABC. I later put a Webra 32 on the same plane and it acted like it was on steroids! I think the OS 28 FSR is in the middle of those two. My OS 28 FSR is noticably more powerful than my 2 OS 25 FABC's. I really think they should work great on your 20 sized Taurus. The 32 will be HOT. Should be alot of fun. They should all use the same bolt pattern, even though they weigh different why not try them all out!!!
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