Apologies if this is reposted but my first "send" never appeared on the server. I have a couple of questions that I hope to get answered. This was my first. The model is an Fascination-50 pattern ship. for those who do not know it. It is vertually a clone of the Venus 40. I built it for practising the sportsman and standard schedules. Now my Venus
40 whichis fitted with an ASP65 FS seems to be best on a master Prop sized
13 X 6. Any thing smaller and it cuts, but that is no problem because it is just about right anyway. My Fascination-50 however has a SC52 two stroke. I started flying it - bear in mind the engine was new out of the box with a 12 X 6 master prop but as a bit of curiosity set in I tried an APC 11 X 8. Apart from going like a bat out of hell I quite seem to like flying with it although the throttle has to be held back in level flight else it takes on all the airs and graces of a pylon racer. Now, guys out there. More knowlegeable than me. (Only been back after and absence of about 20 years) what props would you suggest?
Kind regards and thanks in advance to all replyees (new word?)
I would use an APC 12x6, maybe a 13x5. Chuck the master airscrew prop. Too much flex for me. Speed is not your friend in pattern. You want good steady pulling capability.
As for heating and re-pitching them, *I* don't think that is a wise move unless you have all the right equipment to measure pitch from root to tip before and after the new values are set. That is ignoring the fact that many plastics get a new bending modulus once you heat them up.
Your milage may vary and you may really be a rocket scientist...
I live in a rural area and have never seen ayone fly pattern. I have always thought that for precision aerobatics, lots of steady pull would be the desired power delivery. But I'm always perplexed when I see the listing for "Pattern" props in the catalogs, and they all seem to have outrageous pitch:
11x12, 12x12, 14x14, etc. (these are actual APC "Pattern Propeller" listings from Tower).
On Tue, 26 Sep 2006 20:21:31 GMT, "Six_O'Clock_High" unless you have all the right equipment to measure pitch from root to tip
I haven't (and won't) try the repitching myself.
I gather that the folks who do it know what they're doing. They fly a lot. If the repitching was weakening the props, I think they would have found that out by now.
I don't know what kind of equipment they use, either.
On Tue, 26 Sep 2006 21:08:27 GMT, "Robert Scott" wrote in :
I'm not sure.
One of the elements in competition is making sound standards. There used to be a reward given to planes that sounded quieter in the air. Now it's just a sound check on the ground.
In the earlier days, too, there were restrictions on displacement (.61 for two-strokes, 1.20 for four-strokes). There is no limit now.
Lastly, the old planes mostly used retracts.
It may be that the props with outrageous pitch helped with prop clearance, power, and sound. The planes flew fast and used momentum to draw vertical lines.
I get the impression that the new designs are turning props in the 16" to 18" range, more or less. As a general rule, they do seem to be pitched higher than for 3-D designs.
I've crashed all my patternish planes. I read the NSRCA e-mail, but I haven't got a plane now that will meet the specs for competition. I would like a gasoline-burner for economy, but getting enough power out of a gasoline engine in an 11-pound airframe is hard.
As is happening elsewhere in the hobby, many of the big dogs are going electric.
Marty, I don't know about the prop thing, but *I* wouldn't.
I have a BME 44 (they don't make them anymore) with a Pitts muffler and on an old Hangar 9 Cap 232 came in around 13 pounds 8 ounces. I know it can be built lighter...
I agree that a "steady pull" is what is needed and to digress one moment I wish the limit was set on the engines at say 10cc for 2st and perhaps evens the same for 4 st; this would develop the potentioal of these engines. Also very little consideration is given to the sound output level aprt from the ground sound level check. I seem to be ending up like all the rest with high piched props, certainly when compared to say 3D with the other extreme pitched props.
On Wed, 27 Sep 2006 04:33:27 GMT, "Six_O'Clock_High" an old Hangar 9 Cap 232 came in around 13 pounds 8 ounces. I know it can be
Getting rid of 2.5 pounds is hard.
There was a brief rumor a few months ago that the FAI might lift the weight limits for pattern competition. That would improve the odds of being able to use a gasser. It might also tilt the playing field in the direction of biplanes, if the 2-meter box is kept.
The very high pitched pattern props you have seen advertised were used when folks in pattern were trying to quiet down their two-stroke .61 powered models while running engines that were tuned to produce their maximum power at lower rpms than "normal" two-stroke glow engines.
The OS .61SF/RF/Hanno Special and the YS.61AR was designed to spin such props comfortably.
The SC.52, unless specified in the instructions as being designed to use larger/high pitched props, is probably struggling to keep from overheating while using the props you have suggest. You will most likely end up tuning your high speed mixture very rich in order to keep the engine's timing retarded enough not to over heat. I have heard that there are Sanye .52 engines available in England that are designed to pull larger load props and lower rpms. I'm not familiar with this particular SC .52 engine. So, if the props you are using are actually recommended by the distributor, never mind what I am saying.
Depending upon which class of maneuvers you are trying to fly, if your model is expected to climb vertically for extended periods, you will be better off using larger diameter, lower pitched propellers, such as a 12x4 or a 13x4. If your engine will pull the 13x4 without protest, I would work with it for a while and see if it will do the job for you. Unfortunately, such props do lower your models top speed. This might or might not be a problem for your model and your style of flying.
A 12x6 and an 11x8 are typically considered to be .61 sized props. Special porting/timing of a smaller engine can make these suitable choices, but I don't think there are many engines around in the .52 size that will handle them well. Just my opinion.
I just purchased an ASP .52 two-stroke and am curious to learn how it has been tuned. The Magnum, ASP and SC are all made by Sanye.
The subject of propellers, This comes up everytime there is a newer type of model plane category or newer flyers. It came up in the 50's when control line speed flying was the interst,it came yp when pylon racing became popular, it comes up now when the choice of engines style of flying. Please remember that a prop is nothing more then a wing,it has to move through the air to produce "LIFT"or for this info thrust. So to be efficient it has to produce "lift" with the minimum of drag,at very high speed through the air,... Now rpm is not all what is needed it has to produce lift or thrust, as the minimum of drag. Given any prop.for comparison if one relies only on r.p.m. he wont get t enough thrust needed to propel his airplane through the air, if too much drag the airplane will tend to yaw and also possibly dive to the left,( if we are refering to our standard revolutions now on our usual engines.) and not enough or too much pitch will result also in the speed forward to be affected. Now it has been an almost standard advertizing info, "OUR PROPS WILL REV UP 1,000 RPM MORE THE OUR COMPETITORS" well it all depends what is difference in the blade THICKNESS, and if it realy has the same pitch. ( a difference of 1/2" less average pitch will give a lot more RPMs. So the only way to verify the pitch is to have a pitch gage, it not need to be a very sofisticate thing, as what we wnat to find out is if there is a difference in the pitch, Also how much thicker is the average of the blade plus the width. So a wider blade that is thinner might give more thrust at a lesser RPM then a thicker one at higher rpms. Going back to Pylon racers,we know that those flyers will not release the model if they don't get 22 to 23 thousands on the ground,but if the crew doesn't give a tremendoud PUSH the plane may not get off the ground on the area allowed for take-off, but look at trhe sped they acheive once airborne So starting with the experience gathered over the years,one starts with the average established sixes for a given engine,matched to a given airplane, so if one wants lift power to lift a heavier plane what is needed is tha capacity to produce enough forward speed to make the wing effecient enough to lift the airplane. (providing the wing has the proper thickness and the proper airfoil, ) So a given engine, (.40) using a 10x6 at 12,000 rpm) from one maker may not produce the PULL to get the wing to lift the plane but changing to another maker might, also a wider thinner blade will produce more thrust then a narrow thicker one assuming the rpms are the same.
It is best also to look what is used at the club flying field and use the prop that is the most popular there for a start, Many times I have had to help out, the new flyer can;t get the performance needed to fly correctly, and going to my car and produced one of my most used prop, has resulted in a better flying plane in fact it attained the proper speed to get the wingf to lift the model with a more safe flyinf speed.I hate to add this, but many times the sales person ad the hoibbyshop is not informed enough in this subject amd will not sell the proper prop, he will sell the one that is advertized the most, but some times also some of the flyers at the field will fall for the ad.as as far as they are concerend it flies their plane well enolugh, and they have np idea that it can be improved.
"Ed Cregger" wrote in message news:G7uch.19659$ snipped-for-privacy@bignews5.bellsouth.net...
Searching the web for feedback on the Facination and we are touchin
home base here. I recently bought one to practice F3A after an absens of 10 years from competition and found that this is one sweet flyin pattern plane. I have started with a wood 11x8 but will soon b experimenting with larger diameters and lower pitches as I am using a OS 55 AX pulling this craft a little to fast for my liking. Welcome to be in touch on snipped-for-privacy@gmail.co
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