Scale Pitts S1-T, S1-S, and a Challenger.

[Jaketab]

Ace,

Not to get into an Ackerman discussion, but sometime back I was fortunate to discover a Pull Pull calculator that measures all different parameters including the slack in the wires. As long as the wires are not crossed and both pivot axis is on the hinge line (no offset) then there is minimum slack in the wires. The slack calculates to .004" with a 2.25" servo arm and a 3.125" rudder arm. I do plan to use an SWB servo tray similar to the one posted above. I have this same set up on my Delro Turner W4X with no slack in the wires. The shakey part for me is getting the rudder horn exactly centered and in line with the hinge line.

Thanks - J Tab

 

[Jetpainter]

@Wacobipe what brand is that tray?

 

[Jaketab]

Jetpainter - from looking at the pic, the tray appears to be a Seacraft.

 

[Jetpainter]

Jetpainter - from looking at the pic, the tray appears to be a Seacraft.

Thanks! I was on my tablet and couldn't see the file name for the picture or read the markings on the tray. Now that I see it on my desktop it's plain as day.

 

[acerc]

Ace,

Not to get into an Ackerman discussion, but sometime back I was fortunate to discover a Pull Pull calculator that measures all different parameters including the slack in the wires. As long as the wires are not crossed and both pivot axis is on the hinge line (no offset) then there is minimum slack in the wires. The slack calculates to .004" with a 2.25" servo arm and a 3.125" rudder arm. I do plan to use an SWB servo tray similar to the one posted above. I have this same set up on my Delro Turner W4X with no slack in the wires. The shakey part for me is getting the rudder horn exactly centered and in line with the hinge line.

Thanks - J Tab

Being an ex auto mechanic I understand Ackerman well. I usually use the rudder horn to mark the dimensions for the servo arm to follow. Then I make a servo arm to suit my needs. The servo arm can be made with different lengths to control the throw range, just have to follow the same dimensional lines previously drawn. In the pic the three black circles are where the rudder servo horn pivots and connections are made. The red circles are where the rudder links were, the difference was my measurement for 100% servo operation with proper rudder deflection. As long as the control connection runs on the line there is no slack in any position.

 

[acerc]

Woo Hoo! My shop will be here tomorrow, it will take about a week to get it enclosed and set up. So! I have ordered the items I know I will need, servos, battery, and the Rx. I have decided I am going to give theGP123 a shot. The mfg shows better performance than the DLE 120 and with the recommendations from you guys I feel comfortable it will do the job nicely. More to come soon!!!

 

[Jaketab]

With lower wings framed up, I'm ready to start on the upper wings of the 58% Pitts.
Any major difference - advice or precautions before beginning ??????

Thanks - Jaketab

 

[acerc]

I have always found leaving the abutting ribs, inboard, unglued until the two halves can be butted together very beneficial in perfecting the joint.

 

[Jaketab]

Ran into a slight problem before starting the upper wings on the Pitts 3.04.
The building rails are warped (twisted) to the point I do not feel comfortable using them to build the upper wings. The rails appear to made from a dark wood (possibly walnut). It takes more force then a nail can provide to keep them flat on the building table. I was able to salvage 2 of the rails for the shorter lower wings.
Because the upper wings are longer, the full length of the rails is needed. If the rails are nailed flat on one end – the twisting or warping of the rail prevents the other end from laying flat on the table.
Picture attached. Hard to document with photo.

One solution may be to cut out the good center sections and use 2 good sections of the rails end to end to make 1 full length rail????

Jaketab

 

[acerc]

I would not splice them. If it were me I would try soaking overnight, alcohol works real well if you can make a tube for it. And if those do not feel right I would pick up some Poplar and cut new ones.