X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 03 Mar 2010 08:47:18 -0500 Message-ID: X-Original-Return-Path: Received: from smtp-auth-01.mx.pitdc1.expedient.net ([206.210.66.134] verified) by logan.com (CommuniGate Pro SMTP 5.3.3) with ESMTPS id 4150619 for lml@lancaironline.net; Wed, 03 Mar 2010 08:38:09 -0500 Received-SPF: none receiver=logan.com; client-ip=206.210.66.134; envelope-from=rpastusek@htii.com Received: from HTBOB001 (unknown [63.164.254.188]) by smtp-auth-01.mx.pitdc1.expedient.net (Postfix) with ESMTPSA id 85F96847D6 for ; Wed, 3 Mar 2010 08:37:30 -0500 (EST) From: "Robert Pastusek" X-Original-To: "'Lancair Mailing List'" References: In-Reply-To: Subject: Pitch trim control - IV-P X-Original-Date: Wed, 3 Mar 2010 08:37:18 -0500 X-Original-Message-ID: <005b01cabad6$ad7034a0$08509de0$@com> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_005C_01CABAAC.C49A2CA0" X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: Acq60FGx9rI66PaaSAO3BHx6/r+0egAAzKpg Content-Language: en-us This is a multi-part message in MIME format. ------=_NextPart_000_005C_01CABAAC.C49A2CA0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Bill, I'm hoping one of our aero engineers will comment more intelligently on your discussion/questions below, but let me give it a start. At the speed our Lancairs fly, mass balancing the control surfaces is important. Even small imbalances can lead to flutter, especially as the hinges and multiple control system linkages wear a bit over time. I would encourage you to balance especially the elevator and ailerons as well as you can---after paint. A number of builders have had the same problem with getting enough weight in the tips so someone (Lancair?) developed a "bobweight" that could be added to the control arms in the tail. I have not actually seen one, but understand that it consists of a steel arm that attaches to the center elevator hinge assembly and extends forward toward the front of the fuselage. You can then add the necessary weight to the end to balance the total elevator assembly. If one of you has used this system, could you elaborate? Thanks, Bob There's an article in the EAA Experimenter about Paul Lipp's 235. Among other mods he describes spring-loading the aileron trim but using a trim tab for pitch. The way I picture it is that a trim tab maintains its relative effect with change in airspeed whereas spring loading will change. (The spring would compress due to the additional load on the surface, allowing the surface to deflect). I don't know enough about the subject to say one way or the other. My question is- do those with the spring-loaded pitch trim have to adjust trim very often as their speed changes? My reason for asking is that my IV-P elevators are going to need more lead than I can pack into them. I've been thinking about a spring-loaded system for trim so I can lose the weight of the trim tab and MAC servo. What I have in mind would be a fiberglass leaf spring that would act in both directions. Although I'd like to use a mechanical control I may end up using a linear actuator (Velocity builders might recognize that setup). Looking for comments- Bill Wade ------=_NextPart_000_005C_01CABAAC.C49A2CA0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Bill,<= /span>

 

I’m hoping one of our aero engineers will comment = more intelligently on your discussion/questions below, but let me give it a start.  At the speed our Lancairs fly, mass balancing the control = surfaces is important. Even small imbalances can lead to flutter, especially as = the hinges and multiple control system linkages wear a bit over time. I = would encourage you to balance especially the elevator and ailerons as well as = you can---after paint.

 

A number of builders have had the same problem with = getting enough weight in the tips so someone (Lancair?) developed a = “bobweight” that could be added to the control arms in the tail. I have not actually = seen one, but understand that it consists of a steel arm that attaches to the = center elevator hinge assembly and extends forward toward the front of the = fuselage. You can then add the necessary weight to the end to balance the total = elevator assembly.

 

If one of you has used this system, could you = elaborate?

 

Thanks,


Bob

 <= /o:p>

 

  There's an article in the EAA Experimenter about = Paul Lipp's 235. Among other mods he describes spring-loading the = aileron trim but using a trim tab for pitch.

 

  The way I picture it is that a trim tab = maintains its relative effect with change in airspeed whereas spring loading will = change. (The spring would compress due to the additional load on the surface, allowing the surface to deflect).

 

  I don't know enough about the subject to say one way = or the other. My question is- do those with the spring-loaded pitch trim have = to adjust trim very often as their speed changes?

 

  My reason for asking is that my IV-P = elevators are going to need more lead than I can pack into them. I've been = thinking about a spring-loaded system for trim so I can lose the weight of the trim tab = and MAC servo. What I have in mind would be a fiberglass leaf = spring that would act in both directions. Although I'd like to use a mechanical = control I may end up using a linear actuator (Velocity builders might recognize = that setup).

 

  Looking for comments-  Bill Wade

------=_NextPart_000_005C_01CABAAC.C49A2CA0--