TBM Magic Hand 87" YAK Detailed Build Thread

[john5909]

kevin , the yak's looking good. quick question on the fuel dot & filter ,my yak came without the fuel dot & fuel filter (tank not assembled or installed) missing wing bolts & missing the rod ends. john was mistified but did send the rod ends and the wing bolts,still out for a fuel dot and filter,do you know the size of diameter for the dot and filter? keep the pics coming! looking good!

[kevinf2501]

John

For the fuel dot I would go with a
http://www.troybuiltmodels.com/items/HAN115.html or
http://www.troybuiltmodels.com/items/MPIACC229.html

For the filter I dont use any inline filters and removed mine. I filter my gas through the Jersymodeler electric gas can. I have found the inline filters and carb screens cause more problems than they solve.

Kevin

[john5909]

kevin , thanks much for the info.

[maineflyer]

Looks good Kevin! How do the gear look?
Jeff

[kevinf2501]

More Progress. I glued in the firewall and then added the tri stock to reinforce the firewall.
When doing the tri stock all of it except 2 pieces have a 90degree angle these 2 piecee are for the bottom of the motor box as the bottom piece slops at an angle (See pic)
I also trimmed the tri stock and test fitted it around the standoffs and inter bolt holes before glueing. If you dont trim it out the tri stock covers the motor mount holes. (See pics)

The tri stock pieces do go in specific locations as they have angled pieces and different lengths, however they arent marked so if you like jigsaw puzzles enjoy . Once the epoxy cures I will sound it down flush with the motor box and make it look pretty.

I did leave the top of the motor box of for now so I can work inside to mount the motor and do the throttle servo and hook up the gas tubing.

[kevinf2501]

The landing gear and tailwheel mount fairly quickly. I really do like the wheel pants and the way the mount onto the gear with a molded inset. this also prevents them from turning.

The only issue I had with the main wheels was the bolt holes in the gear for mounting the wheels is not the correct size. I drilled the gear and the wheel pants to 3/16 and the bolt fitted in nice and snug. I used a 1/4 inch drill bit to drill out the rudder for the gear assembly. Be far enough into the rudder not to hit the robart hinge as the pin goes in a far way. I used gorilla glue for the pin so it would fill in and expand giving at a good solid install.

[kevinf2501]

Finally got servo's today. I have 3 CS170's (5955's branded for tower) and 2 5955's
So my goal is to get it pretty much finished this weekend.

Look for More Pics
Kevin

[kevinf2501]

The rudder pull pull instructions in the manual are easy to follow. The only thing not mentioned is the distance from the rudder to the clevis for the pull pull. The correct distance is half of the control arm width between the cables. If using the purple on included the width is 3". therefore the clevis on the rudder should be 1.5" from the center line of the rudder.

I used the purple arm provided and mounted it onto a composite Hitech servo disk that I got with my 5955 servos (just ground of the highspot) the red heavy duty hitech arm will work as well.
The ball joints are a little stiff and should loosen up with use. I used all the included hardware

[kevinf2501]

A note on drilling out the Elevators for the control horn bolts. the manual shows to use a 4mm drill bit. This is to big for the supplied hardware (3.7mm) I used a 9/64 drill bit (3.4mm) this makes for a nice snug fit when screwing in the control horn bolt. I uses some loctite when screwing on and tightening the aluminum supports to stop them coming loose and allowing the bolt to turn.

The location of the control horn bolt is specified in the manual. The manual shows to set a 103mm length for the control rods which is the correct length, however the supplied rods are to long and you will have to cut 10-15mm of the control rod to get to 103mm. The biggest servo horn you can use is a 1" otherwise it hits the bottom of the elevator.

I used all the hardware as supplied.

[kevinf2501]

A note on drilling out the Ailerons for the control horn bolts. the manual shows to use a 4mm drill bit. This is to big for the supplied hardware (3.7mm) I used a 9/64 drill bit (3.4mm) this makes for a nice snug fit when screwing in the control horn bolt. I uses some loctite when screwing on and tightening the aluminum supports to stop them coming loose and allowing the bolt to turn.

The manual does not show a measurement for the control horn bolt. I used 8 mm back (same as the rudder and elevator). As I am using 1 1/4" arms I used 1" offset from the mid point of the servo to locate the bolt. (8mm deep, 1 Inch across) The hardpoint is located towards the wing tip.

The manual says 85mm for the length of the control horn. Once again the supplied rods are to long and need to be trimmed. Mine came out to 80mm and are both identical. I think the geometry on the ailerons can be better. If I was using lower torques servos I would change out the ball link on the servo arm to make it lower. As I have 330oz of torque from the CS170 I am going to leave using the stock parts and setup.

[kevinf2501]

Well the motor is finally on. I spaced it off an additional 1/4" to move avoid a CG issue. I also took some 3hr epoxy diluted with denatured alchohol and coated the motor box inside and out a well as the wing saddle balsa. This adds some strength without any additional weight, not to mention some fuel proofing. I will post pics of the motor install once I get the cowl cut out.

[JPal101]

Kevin
Two questions, you spaced the motor out and additonal 1/4" what is the total stand off. Also, I noticed you used the stock Hitec servo arms. Why not the aluminum type. I will be building one of these in the next couple of days and appreciate all of the tips.

[kevinf2501]

The total distance from the firewall is 6 7/8th I will measure more precisely when I take the cowl of to finish the ignition and battery install. I will also upload pictures of the standoffs motor mounting etc as well a the standoff sizes.

As I have used tons of 5955 servos I have a ton of the composite 1" and 1 1/4" heavy duty control horns I typically cant/wont use on the 100cc and 150cc planes and use 1 1/2" SWB's on them. I really didnt want to use a $12 servo arm when the composite will work fine and is the right size for this project. Also the the hardware provided with the kit is not 4-40 and would require me drilling out the thread on the SWB arm making it unusable on other projects.

I would not use the standard plastic hitech servo arms however the composites will work fine and are rated for the 333oz torque the servo can produce. Using the composites also reduces the overall cost of the project. I believe Dubro makes heavy duty hitec arms that would also be suitable instead of more expensive aluminum arms.

Dubro composite servo arms http://www3.towerhobbies.com/cgi-bin...?&I=LXD670&P=7 One pack will have 2x1" and 2 x1 1/4" (JR & futaba also available)

Feel free to ask any further questions.

Kevin

[kevinf2501]

Here are pics of the motor installation, prop spacing to cowl and the measurement of the standoffs as well as the cowl cutouts

[JPal101]

How have you guys reiforced the landing gear plate, and did you salvage the stock gear and if you did how.