Dave: I am not at all sure what the impact of the change on the loading of the engine mount "Force Couple" to the firewall migkt be but I have the "GPAS" 5-pt mount and the "Thrust Line" would certainly move up to or above the Pt. of attachment line of the (3) upper motor-mount attatch points.
The biggest issue to Steve @ GPAS seemed to be that of prop clearance. That may well have been because I wished to hold the rpm to 3400 max and the resulting prop rpm would need to be sufficiently longer to get the job done that ground clearance would be an issue. This was not clearly spoken but it is my inferance to what he said. Don Burlington IA 52601 -------------------------------------------------------------------------------- ----- Original Message ----- From: "Dave Arbogast, CISSP" <k...@arb.net> To: "KRnet" <kr...@mylist.net> Sent: Tuesday, February 20, 2007 11:46 AM Subject: Re: KR> Thrust Line issues > Funny, my instructor called them the "Trauma - hawk" because of the T > tail being less responsive to prop wash when you need it the most - > stall recovery. > > Raising the trust-line I would think increases the loads on the upper > half of the firewall. Maybe not enough to worry about, but I sure like > the idea of more ground clearance for the prop. > > -dave > > Colin Rainey wrote: > >>Don and netters >>Something else came to mind the other day when considering the effects of >>raised or lowered thrust line. During flight training to become CFI's we >>were always told that the reason the Piper Seminole was made with a high "T" >>tail as compared to its sister plane the Piper Seneca which had a >>traditional tail (and 2 more seats, but that is another story) is because >>the Seminole was really ear marked for the training market, and so Piper >>wanted the tail in "clean air". This was supposed to make it safer to flight >>train in. I am told that the same designer, later worked for Beech and >>designed the Duchess, which is why so much of the configuration resembles >>the Seminole. >> >>My point for this post is this: while in most cases planes are designed with >>the empennage "in the prop wash", some very successful designs are not. >>These planes seem to experience less pitch change due to the change in the >>amount of prop thrust over the elevator/stabilator, and the change is more a >>function of airspeed/airflow. If by raising the thrust line, one lessens the >>amount of prop wash over the elevator of a particular KR2 or S, that builder >>may find a nice softening of the effectiveness, without becoming dangerous. >>Then again it may favor one side only, causing good nose up authority, but >>lose some nose down authority. >> >>I would also think that if the builder then used a longer prop taking >>advantage of the greater ground clearance, he might not have any change in >>the behavior of the plane to speak of at all. >> >>Just some ideas for thought. I was once considering a PSRU or re-drive as >>some call them, for my 1915 cc VW original engine. Had I installed that, I >>would have been 4 to 5 inches higher. This may be an issue many builders >>have contemplated or evaluated. >> >>Colin Rainey >>brokerpi...@bellsouth.net >> >>_______________________________________ >>Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp >>to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net >>Post photos, introductions, and For Sale items to <A >>HREF=http://www.kr2forum.com/phpBB2/index.php >>please see other KRnet info at http://www.krnet.org/info.html >> >> > > _______________________________________ > Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net > Post photos, introductions, and For Sale items to <A > HREF=http://www.kr2forum.com/phpBB2/index.php > please see other KRnet info at http://www.krnet.org/info.html >
