Ichy

Got my new Yak last week and have started to put it together. I am posting here so if you see me doing anything stupid (like I did with my WH Extra 300) let me know! Using a motor that I have not seen here before.

Ichy

This motor is 48 cc. I purchased two of these for my other project, a Don Smith plan 120" WS Douglas Invader.

Ichy

So, I need to break in these engines, plus this is my first experience with gas. Now about that stupid thing! I tried to fly the Extra 300 with this motor. Let's just say it did not work. Being a twin cylinder it does not put out the power that the 50cc singles do. But I do like them because there is almost no vibration.

I am hoping the Yak being 4 pounds lighter and with the smaller wing will be a much better choice this time. The packages arrived with the usual wear and tear that UPS is known for. [:'(] Only two miner issues, which I can fix, I think, I hope! The first is the canopy which has a broken part at the top back. But if I move it back and cut off the rest I think it will be OK.

Ichy

Second problem is on the cowl. Hard to see but there is a dent and a crack in the paint.

Ichy

Started looking at how to mount the motor today. With the 1.75" stand offs that I ordered with the motors they make the prop stick out 0.75". If I move the cowl back and cut off an inch (which would get rid of the crack as well) I am now at 1.75" If I do not use the standoffs I need to make something that is at least 0.25" so that the cylinders do not hit the motor box. So the question I have for you are, how much clearance should I have between prop and cowl, 0.25 inch? I could mount the motor right on the fire wall but would have to notch the sides of the box, which would weaken it right? But that would also move the weight back that much more. Probably only talking 1/8" or so. And what about heat from the cylinders on the wood?

whaturi

what motor is that? weight? what prop?

Ichy

Sorry, forgot to mention that! http://www.ywengine.com/yw48b2.htm Comes from Korea. I bought these several years ago now and the dealer here in the states has this up on his web site: http://ywengines.com/

Tired Old Man

My Feedback: (1)

Leave the engine sticking out the cowl. Protruding farther out on a round cowl plane helps with propeller efficiency.

Ken Bryant

My Feedback: (10)

First issue I see is weight, that engine has to weigh more than a single 50 let alone a DA 50.

I think I would try to move that engine as close to the firewall as possible. If you have to cut wood just add reinforcment to the remaining areas. For instance you can Pin/Dowel firewall. Also you can add reinforcment to the inside of the firewall with angle bracing.

Another possibilty is to MOVE the firewall back. Tom wrote about doing it in another YAK thread. Really not to tough as long as you dowel/pin it.

That nose weight is going to be your biggest battle I think.

rctom

I suggest that you mount it without the standoffs and see where yur weight/CG is. If it balances at that point then shorten the cowling and you're done. If it's tail heavy then you'll need to move the engine out, maybe make some plywood spacers to get the proper spacing.

TF

Ichy

I'll continue on with the rest of the plane, then determine c.g. FYI the difference in weight is 120 grams plus a little for the muffler(s) compared tot he DA50R. About 0.26 pounds heavier.

Ichy

Gettin' close! I cut some dowels for standoffs at one inch just for kicks (and a starting point). Got most of the assembly done. Placed the electonics and stuff inside (not secure just general location). Then started to bolt on the mufflers and found they hit the engine box. If I leave the motor at 1 " then will have to cut off about 1/4 inch of the bottom of the box which will not effect anything. If I have to move the motor back any farther then major surgury. Placed the rudder servo inside but did not do the cables yet. Tonight I'll borrow my wife's finger and see where it balances!

Oh, and before I forget my manners again, Thanks for your help!

Ichy

And the winning number is ......... 3" I am pleasently surprised. I will continue to finish putting things together and trimming the cowl and canopy and such. Will remeasure again when that is done. The batteries are back at the end of the tray as is the throttle servo. I am going to order a better prop. What do you think of a carbon fiber spinner? Is it worth it?

The bird man

A lot of folks are using these.
http://www.espritmodel.com/index.asp...OD&ProdID=4628
They are inexpensive and I hear they are lighter than their CF counterpart!

Tired Old Man

My Feedback: (1)

Very good spinners. Take an impact pretty well too[:@] Truly, they are great spinners and the cost of a 3-1/2 to 4" spinner is not much different from a no name aluminum one. Absolutely less expensive than a Tru Turn and a lot lighter.

Ichy

Thank you for the spinner tip! Just ordered one.

Ichy

OK! Well got my new prop, a XOAR 20 x 8. Got the spinner, but I don't think I purchased the right size, 3". Should have been a 3.5" which is what I had in aluminum. What was I thinking?

Got the motor mounted using the 1 " wood spacers. Had to cut a portion off the bottom of the engine box like I said earlier. I have about 1/8 " clearance between exhaust and wood. Enough?

I am using an optical engine kill switch from Electrodynamics (salvaged from the Extra 300) which is installed along with the engine electronics. Fuel tank and plumbing is in. Started on the pull pull rudder stuff. Sorry this is taking so long. I hate work! [:@] But there is not that much to do. I am going on vacation next week so will order the new larger spinner. Should be here when I get back!

So ........ How do you catch a unique bunny? Easy....... unique up on it!

How do you catch a tame bunny? Tame way, unique up on it!

Sorry, could not resist! [X(]

rctom

Groan!

Ichy

Darn, they are out of 3.5" and 4". They do have a 4 1/8". Is that getting too large? I would like the center section to be as wide as the prop hub cause the motor has 6 bolts to also hold the prop, so gotta drill the back plate for those as well.

Got other things to do for awhile anyway, so will get back on this in a couple of weeks or so. Take care!

Ichy

Almost to the point of balancing. Got the canopy trimmed, and you can't tell it was ever damaged. All the electronics are in 'cept the batteries. The cowl has been cut down 1 inch and is full of holes for the exhaust and spark plugs. Put white electrical tape on the wires to sorta hide them. Well I tried anyhow! Still waiting for a spinner. Right now it is too cold to work in the garage and too cold and windy to fly anyway. [:'(]

With this type engine do you think I need to put in baffles for better cooling? As you can see the heads do not stick out. Sorry but I did not take a good pic of the exhaust openings.

Ichy

Bet ya thought I fell off the earth! Naw, just waiting for a spinner and good weather. Haven't gotten either. Have been looking for a 3.5" spinner from espirtmodel.com, but they have not had any in stock. So got tired of waiting and purchased a trueturn instead. Got the engine fired up but did not have my tach with me. Sure sounded good! Now have to wait til the snow clears out. Hope to do final balance this week.

Ichy

Snow is gone, sky is blue!

Weight is 15.7 pounds. I have an optical isolater for the servos with a 6 volt 2700 MAh battery. The receiver has a 4.8 volt 1650 mAh. Both Nimh.

Too heavy?

rctom

Not at all.

The 80" Wild Hare Yak is way underrated and highly misunderstood.

The plane will fly well even at 17+ lbs., but I have discouraged people from using a big heavy engine because there is no real reason to do that and I think they will be much happier if they keep it light.

You've added probably 5-6 ounces of battery above what is needed, no big deal. It will still fly fine, I doubt you will even notice it.

TF

Ichy

Thank you Tom! Took the moring off work because today was maiden flight! Took one glamor shot and one taxi picture. Sorry no video. Had a hard time getting the engine started today. My arm hurts now! But, it did start and ran up to 6800 rpm (20x8 Xoar). I had someone much better than me fly it. Needed just a little bit of trimming but it sure looks and sounds nice in the air. It is not a barn burner but should work out fine for my type of flying skill level. Motor has less than a gallon of gas through it so I should be able to get more out of it.

Maybe because I put together the Wildhare Extra 300, and had some building experience, that this one went together very nice. I am more than happy!

Nice background today for flying.

Tired Old Man

My Feedback: (1)

Looks good!