Kang,
Thank you for the interesting information. Obviously with a smaller diameter the Froude efficiency will drop slightly but the efficiency related to P/D ratio could be improved, certainly in the later stages of the flight if the VP lowers the blade angle. Has this been discussed at all?
John Barker - England
From: Indoor_Construction_at_yahoogroups.com [mailto:Indoor_Construction_at_yahoogroups.com]
Sent: 03 April 2015 03:35
To: Indoor_Construction_at_yahoogroups.com
Subject: Re: [Indoor_Construction] ECh Day 2
Both Cornel and Zoltan's model used a spacer of 200 mg, so for the airframe, they are flying the old rules models. Zoltan moved his rear hook from 1-2" behind the wing to just in front of the rear wing post. Popa did the same. A spacer is still used to make up the length between the hooks. Cornel's rear hook position remained in the same place as his old rules model.
Their models have very fast climbs to 160 to 165'. I estimate that in the first minute, they reach 100'. Once to the top, the models have very efficient cruise and descent. The combination of an aggressive climb and efficient cruise/descent is what most people struggled with. For models that don't have the right combination, when trimmed for a good climb, the trim would be under elevated in cruise and descent. If the cruise trim was good, then the model would stall in the climb. The difficulty is likely exacerbated in the new rules models that don't have the right combination of stick bow and twist. The right amounts are necessary in the climb and cruise portions of flight. Models with short hook-to-hook distances modified from old rules motor sticks have trouble getting the right combination.
Exceptional rubber and winding really really hard are the final requirements. When you fly to 160' and dead stick on the descent, you know that more turns are needed. All of the top fliers put a huge number of turns in their motors.
As always, exceptional times come from exceptional trim and rubber. The high performances are due to pushing the limits rather than to the new rules. The limits can be pushed because with the smaller motor, the new mine, at 180', is akin to having an unlimited height.
Zoltan used a new small 16.5" diameter prop. Cornel's was ~18.3" and shortened from his old rules prop of ~18.9". Last year, Brett and I used 18.3" props. Cornel's average RPM was about 46 and Zoltan's about 55. It is likely that a smaller prop with thinner rubber, climbing at lower torque, makes the climb easier to trim. But is the smaller prop more efficient in the climb than the larger prop? I don't know. If it's true, it's not for reasons obvious to me. Is the smaller prop more efficient in cruise and descent? I don't think so, but I also don't really know.
---In Indoor_Construction_at_yahoogroups.com, <tapio.linkosalo_at_...> wrote :
Most people seem to be pushing in the 20 to 23 minutes range, yourself included. I recall you mentioned before that you fly with your old rules models, using 2/3 motor and 1/3 ballast, is this what others are using too? It seems that Zoltan and Cornel and Popa have cracked the new rules, discovering something to adapt their models to the new rules? What is that? In previous message Karol mentioned that people are desperate for smaller props, so is that together with thinner motor the answer for longer flights?
I am impatiently expecting a report / an analysis of the models of the winners!
-Tapio-
Received on Fri Apr 03 2015 - 03:01:38 CEST
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:48 CET