Alan Resinger · Nov 09, 2001 11:08 AM
#0 sourceSeveral months ago Chris Cox and I decided to build new models for the Saito 56 4S. Not wanting to re-invent the wheel after seeing what was going on in the Eastern US, we decided to build a proven design with a lot of 4S experience behind it. Chris had attended the last two WC as a member of the Canadian FAI team and had been impressed with the performance of the Berringers at the last WC in France. Several letters produced plans and several pages of information on the designs that Gilbert has been campaigning in Europe for the last 15 to 20 years. He has ben using 4 strokes all this time so he must know what he is doing.
We decided to build the Sportster model as we both liked the lines better than his Sukoi. The plans also had a detailed drawing of the venturi to be used in the Saito. With only slight modification in the wing construction method we are fast on our way to completeing these models. Gilbert stresses that the model has to be below the 1500 gram (that is 52.9 oz for you non-metric guys). This is not a beginners model and the weight is tough to attain.
Now getting to the propeller. Gilbert also can supply some parts for the model like a carbon cowl and carbon wheel pants. He also offers for sale a laminated wood propeller that is 13.5" in diameter and has a pitch of 7" at the root and 3" at the tip. I thought the pitching to be a bit unusual so I went back and read some of his design info. To quote, "The big diameter and low pitch at the the blade tip allows an enormous static thrust to be produced. On the other hand, in case of an undesireable overspeeding, the angle of attack at the blade tips becomes negative, so the propeller acts as an aerodymic brake." the prop is laminated and weighs just 15 grams lessening its gyroscopic effect.
At Clovis, CA several weeks ago Ted F and I were talking about the prop during dinner and were questioning the rational of the pitch arrangement. While in CA one of the other competitors ask me for plans for the Firecracker I was flying and upon returning home I dug through the plans box to find the set to be copied. I also got out the Firecracker article that was published in the Austrailian magazine Airbourne. Brian Eather has always impressed me with his knowledge of PA and in the article he writes, "I like large diameter props as they enable the model to fly slower (at the expense of some turning ability), they act as a brake in a dive and they load the engine sufficiently without having to use excessive pitch. I make my own wooden propellers of 13" diameter and with 5" pitch at the hub, 6 1/2" pithc at the mid span and 5 1/4" pitch at the tip". Seems to me like I'm looking at somewhat the same thing that Berringer is using with great success today. Maybe we haven't tried enough experimentation on the props we are using for non-piped engine set-ups.
How about some comment from our resident experts. Brett, Ted, David and Paul should have some feelings on the issue. Knowing the amount you guys fly, you probably have done some experiments and I'd like to get your impressions. I still think there is a lot we could do with conventional set-ups by improving props. With lots of people going to the 4S it is probably time to look into it.
We decided to build the Sportster model as we both liked the lines better than his Sukoi. The plans also had a detailed drawing of the venturi to be used in the Saito. With only slight modification in the wing construction method we are fast on our way to completeing these models. Gilbert stresses that the model has to be below the 1500 gram (that is 52.9 oz for you non-metric guys). This is not a beginners model and the weight is tough to attain.
Now getting to the propeller. Gilbert also can supply some parts for the model like a carbon cowl and carbon wheel pants. He also offers for sale a laminated wood propeller that is 13.5" in diameter and has a pitch of 7" at the root and 3" at the tip. I thought the pitching to be a bit unusual so I went back and read some of his design info. To quote, "The big diameter and low pitch at the the blade tip allows an enormous static thrust to be produced. On the other hand, in case of an undesireable overspeeding, the angle of attack at the blade tips becomes negative, so the propeller acts as an aerodymic brake." the prop is laminated and weighs just 15 grams lessening its gyroscopic effect.
At Clovis, CA several weeks ago Ted F and I were talking about the prop during dinner and were questioning the rational of the pitch arrangement. While in CA one of the other competitors ask me for plans for the Firecracker I was flying and upon returning home I dug through the plans box to find the set to be copied. I also got out the Firecracker article that was published in the Austrailian magazine Airbourne. Brian Eather has always impressed me with his knowledge of PA and in the article he writes, "I like large diameter props as they enable the model to fly slower (at the expense of some turning ability), they act as a brake in a dive and they load the engine sufficiently without having to use excessive pitch. I make my own wooden propellers of 13" diameter and with 5" pitch at the hub, 6 1/2" pithc at the mid span and 5 1/4" pitch at the tip". Seems to me like I'm looking at somewhat the same thing that Berringer is using with great success today. Maybe we haven't tried enough experimentation on the props we are using for non-piped engine set-ups.
How about some comment from our resident experts. Brett, Ted, David and Paul should have some feelings on the issue. Knowing the amount you guys fly, you probably have done some experiments and I'd like to get your impressions. I still think there is a lot we could do with conventional set-ups by improving props. With lots of people going to the 4S it is probably time to look into it.