Composite-ARF 3M Yak 55 sp Build

[eagle1]

Finally after 6:00pm I finally got brown to bring my engine to my front door, then I had to go out on our "Date Night" to eat then go look at living room furniture, after a full belly and an empty pocket I am able to mount the DA-170 on the front of this beast!
I measured and marked the firewall yeasterday, then checked it with the engine, I ended up with 7mm to the pilots left of the centerline instead of 5mm, I drilled the first hole, did not work, engine was toooo low, so I drilled another hole 4mm higher on the fire wall, Bingo, right on the money, I need a little more shimming of the engine, I have 1in standoffs but only have 2mm clearance on the right side, the mounting bolts I have are not long enough for thicker standoffs, so I have to wait until tomorrow to buy the right size bolts, so tell me what you think I think it is looking more like an airplane now.
I have to go mount the cans and see if everything will fit juuuust right. so we'll see if I can get this bird ready for Sunday, it's looking tight right now

[Tex]

Eagle take your time and make sure its all tight, thats a bad azz plane. Looks sharp.

[pepatrick]

You are going to want to use 2" stand offs. Get 3.5" bolts. This gives you enough room to go through the mount, firewall and fender washers. Then I used lock nuts to tighten it up...I tried to follow Comp-Arf directions for mounting the motor..and had to fill my holes back in. I put the plane on its tail (wife holding the plane)...climbed up a latter set the motor on firewall and tied a string around the prop shaft. When the string was the same size on all ends..that was my center point...It came out perfect... Your plane is looking great...cant wait to hear how you like it.

[eagle1]

even though I use blind nuts I always use nylon lock nuts on the inside so there is no chance of it coming loose, I think I am going to use 1 3/8 '' stand off, I think two inches will hold the engine too far for my liking, now if the planes likes it or not I will have to find out, with 1 in stand offs it puts the left side about 2 mm from the cowl, adding another 3/8in will put it about a half inch from the left side, I also have to ad a little left thrust, according to the threads on here, so that will put the engine perfectly in the center, I have the prop drilled and balanced now, I am laminating some balsa with glass weave for the upper and lower baffle plates, I have thought about it and I want the engine to get as much air as I can give it, cans are going to come out in perfect after I space the engine right, then it is on to getting the baffle in place, can mount in place, when that all dries it will be time to balance the plane and mount all the electronics , then............MAiden, we will see if there is enough daylight and night tomorrow to get it ready for Sunday, but no worries I will make sure it is right before I fly, if it cannot be completed by a reasonable time SAt I will wait until next weekend, thanks for your help pep I hope your flies this weekend also let me know how it does

[pepatrick]

I tried 1 3/4 standoffs and it was not enough...Thats why I went to 2" Maybe Compy has moved the firewall forward on the yaks now...Mine would not clear at 1 1/2...so hopefully it will work for you. Also..these Comp Yaks are not consistent with the thrust lines. John (J&J) had to add down thrust in his. I have added no thrust to mine and it is straight as an arrow on the up lines. I would not add anything to it until you fly it. One thing is for sure...You will love how axial this plane is. Im dying to get this 170 fired up and try it out, but it looks like it may have to wait until Sunday...I think it is going to be too windy here...

[JCS]

Hi

I use 40 mm stand-offs. With a spinner that's enough clearance for the prop. Without it's a bit tight, but still no problem. I did mount the engine straight to the firewall, thus no changements to the angle were made. With that setup the plane goes straight in up- and downlines given that the CG is correct. The CG can have a big influence on the upline-tracking.

Jean-Claude

[eagle1]

where is your cg?
I was told that the cg in the instructions was more for 3D

[JagerBomb]

Just as a suggestion. You need a minimum of 1.25 inches of clearance between the prop and cowl. Less than that will make the prop much less efficient. instead of using standoffs you should make a spacer from plywood slightly larger than the backplate on the engine. This will dampen vibration instead of accentuating it

[JCS]

	Quote: Originally Posted by eagle1
	where is your cg? I was told that the cg in the instructions was more for 3D

For Freestyle I fly the CG some mm behind the CG range mentioned in the manual. For IMAC I add approx. 850 g lead to the nose. But I don't know exactly where the CG is located with the nose weight. I will have to check that next time when I get the plane out.

As for the clearance of the prop: JagerBomb is correct. The more clearance the better.

Regarding the stand-offs: I let manufacture some custom stand-offs with extra big backplate. Thus the vibrations are reduced to a minimum. Regular stand-offs might have a too small backplate.

Jean-Claude

[Hammbone]

	Quote: Originally Posted by JagerBomb
	Just as a suggestion. You need a minimum of 1.25 inches of clearance between the prop and cowl. Less than that will make the prop much less efficient. instead of using standoffs you should make a spacer from plywood slightly larger than the backplate on the engine. This will dampen vibration instead of accentuating it

This is what you want.
I used a ply spacer that is @ 2-1/8" thick.

Jim

[eagle1]

I ended up with 1 1/2" of ply plate"standoff" under the engine, the balance for 190mm has everything ahead of the wing tube, I have almost everyting rady for the maiden flight, I have the choke rod in place , cooling slots in the bottom of the fuse for the cans, cans mounted , upper and lower baffle plates, I have to order more servo wire and redo the elevator extensions unless I can figure a way to mount the PBR in a place where I can have the ones I already made work, I have to make the extensions for the rudder servos, I installed the throttle servo against the front bulk head shaft down standing on its end, I have to glass the landing gear plate in place then mount the pbr, I worked on the plane til 2 o'clock last night trying to get it ready, I could have but it would have been half a$$, so next week will be the maiden, sorry I tried, I will have it started tomorrow and take some completed pictures of the plane.
Remember i am going to fly this for 3D

[rdgood]

Hummm,

- this is just my thought on this,
but I would think that you considerably weaken the bottom fuse where you put the cooling holes are.
Jager bomb may have some input here. I would think - ya might want to reinforce with an extra layer of cloth where the holes are. If Im all wet here - please ignore my comments...

Thanks,

Ronster

[pepatrick]

I have seen these hole elongated much larger than this for tuned pipes on this plane. Eagle1 should have no problems with this configuration. There is not a lot of stress on this area and these things are pretty reinforced in the landing gear area anyway...lots of carbon..If you shine a very bright light through the fuse where the gear is, you will see there is a hidden layer of cabon that heavily circles where the struts go in.

	Quote: Originally Posted by rdgood
	Hummm, - this is just my thought on this, but I would think that you considerably weaken the bottom fuse where you put the cooling holes are. Jager bomb may have some input here. I would think - ya might want to reinforce with an extra layer of cloth where the holes are. If Im all wet here - please ignore my comments... Thanks, Ronster

[pepatrick]

A lesson learned today. The DA-170 is an awesome motor, but does not do well the Vess 32B prop. It was so loud I thought my cannisters came undone and was running straight through the pipes. It ripped unlike anything I have ever heard, but had gobs and gobs of power. So..I borrowed a freshly drilled 32 x 10 Mezlik prop from John (J&J tailwheels) and it became the beast that I knew it would. Unfortuanately I blew out the left outter aileron servo (8711) and had to get her down. This is the first time I have had any problems with the 8711s. The Vess 32B is awesome on the 150, but the 170 just has too much power for it. So..a brand new Vess 32b (only 3 flights on it) drilled for a DA-170 can be had for very cheap..

[pepatrick]

Try this for the PBR...it turned out really well. Pardon the hosed display..A new one is being sent and will replace this one.