juvaknin

erland, nice pull-pull solution for your elevator... looks great,
you replaced the fule tank to bigger one? if not, replace it.. the original fule tank it's too small for this big engines...

juvaknin

Here is the last pic i have... me and my Yak-54...
hope next time i'll have Video to share....[8D]

Docvan46

SJN:

I'm envious of your planes, including the ones behind the plastic. The Yak looks like it's on hold while you work on the jet!

Is the jet a true turbine, or is it a ducted fan?[sm=thumbup.gif]

Docvan

Falcon26

juvaknin Thank you for your great pictures and sharing the joy of your first flights and the great information
I have been thinking of a Satio 150 but after seeing that you needed 800 grams or so I am now thinking to better use the weight
saito has a 200 ti Twin 54oz. and a new 220 single 43oz. would you or any of the rest of the guy's think this would be over taxing the air frame and would you think a 17" 0r 18" prop be to big (669 mm - 708mm) would have proper ground clearence I would like your input because on another forum there was a 43cc gaser that caused stress cracks I have great much more comfort with adding active weight than static weight

juvaknin

Falcon26,
i don't think you need this big size engines?!
it's too much... the saito 180 is great for it.. the 150 it's almost almost great...
it's heavy airplane... veryone knows that i didn't find problems when i added 800 grams at the front... the saito 180 fly it great...
this airplane is made of fiberglass and the build of the firewall "inside of the airplane" is very "thin", so i think bigger engine will make you some "cracks" on the front with the time....... put the weight, and make CG arround 140, and enjoy it!!
i recommend on Saito-180! (mine still new and flying very "rich".. and still have lot's of power.. i can't wait to see how it will fly with "max engine power"...)
i also didn't had time to wight the airplane empty of fule... i'll check it and write it to you..

SJN

Docvan, it is simjet 3000 turbine powered.
I have a build thread here: http://www.rc-unionen.dk/nytforum/to...TOPIC_ID=12505

I still need to do some painting on it...but it has flown, as you can see in two of the pics

juvaknin

I don't remmeber who asked me about the total weight ...
so i checked it ... my Yak Total weight is 7.5 Kilograms (kg) without fule in it....

erland

Ouch, 800 grams extra. It looks like i will get away with 280 grams. To get rid of some of the 280g I guess I could lighten up
the back of the plane some. May be by changing some of the linkage to carbon fiber and the rear wheel.

/Erland.

juvaknin

erland, i don't think if you will make the back of the plane lighter, it will give you that much diffrents in flight (with less front weight)...
everyone who got this YAK54.. know that this is heavy plane.. it's nice plane to fly but not for extreem 3D like hovering and stuff... it's good for basic airobatics flights... so i don't think you should start searching wherer to save some weight....
belive me, i added this 700-800 grams.. but it's fly great.. with over-power...
and importent thing... i saw in your gallery the yellow cawul , you must make more opens there! else your engine will get hot and will give you cuts in air....... make bigger hole at the buttom and open 2 lines arround this little slots over there..

ropowell

Juvaknin & Falcon26

I want to add some comments regarding weights and engine sizes. As you know, I have a Saito 150 in my aircraft which balances around 140 mm which seems pretty good in flight. My total weight is 13.5 pounds empty which includes a glow plug heater system and battery AND MOST IMPORTANT, NO BALANCING WEIGHT. I did move the engine forward 18 mm from the point shown on the drawings so the rear face of the prop hub is 188 mm forward of the fiberglas firewall. I mounted my radio battery forward of the firewall (centerline is 115 mm from fiberglas) and also mounted the throttle servo forward of the firewall.

According to Saito, the 150 weighs 890 g and produces 2.5 horsepower. And the 180 weighs 880 g (yes, lighter!) And produces 2.8 horsepower.

As I calculated in a previous post, my wing loading is 32.9 oz/sq ft and my power loading is
13.5/2.5 = 5.40 lbs/HP
Juvaknin, if your aircraft weighs 16.5 pounds, then your wing loading would be approximately 40.2 oz/sq ft and your power loading would be 16.5/2.8 = 5.89 lbs/HP.

THEORETICALLY, the lower the wing loading, the lower will be the stall airspeed and of course, the landing speed. Also, the lower the power loading, the higher should be the climb rate and the potential for hovering.

Now I of course know that there are MANY variables entering into performance of an aircraft but just based on the above calculations, I believe that it is prudent to not rule out the 150 as a good engine choice. It appears to me also that the 180 would be a better choice IF you don't have to penalize it with a lot of balancing weight.

Hope this has been of some interest.

juvaknin

ropowell, good saying..
i'm not going to try any "extreem 3D" with this yak.. so it's just good for me that way...
but tell me, if you moved the engine forward 18 mm, the cawul is fit?? the engine is not too much in front??

about the engines, as i said, if anyone already have the Saito-150 engine.. keep it.. it's not "BAD" for this Yak Airplane.....

juvaknin

ropowell, your yak weight 13.5 pounds, with servos and everything???

SJN

You guys have inspired me to get some action on mine again

I just found out, that the klunk line inside my tank, had fallen off.
I hope this was the problem with my engine all the time.....quitting at half tank....i feel so stupid for not checking it earlier.

I just started the engine up on the table, and it seems to run fine
Just need to get a better 20/8 prop for it. The Dynathrust is not very stiff, and it makes vibrations.


I hope to fly it again in the weekend when I have some spare time.

Falcon26

ropowell thank you for the added information I would like to know the placement of your equipment to achive no added weight and 13.5 lbs I plan on a glow heater for mine as well does moving the engine
18 mm forward crowd the front of the cowl opening and have you moved any other equipment forward as well I would like all tips possible as I am now ordering all the rest of what is needed to complete the Yak for flight

I don't expect the this Yak to be a 3D Super Star but after 30 some years of building and flying from indoor to this type of aerobatic plane weight and function are a quite important part of the fun factor

so once again thank you for all the great input and keep it comming so I can post my progress pictures to the maiden flight pictures and video thanks again

juvaknin

ropowell and Falcon26,
as i remmeber, i read somewhere that this company (CMPro) Airplanes are not the same...
as i remmeber the same Airplanes have "diffrent" weights!!.. and some of them have not small diffrents at all.........
(i'm talking weight "out of the box" without any building........

erland

Hi again,
Here is a list of the things I have done to minimise the weight needed in front.
- I only have 1 elevator servo (instead of 2) and have moved i forward to just behind the undercarriage mounting. For this I use pull-pull.

- I have my batteries as far in front as possible under the cowl.

- I have my throttle servo in front of the firewall.

- The engine is moved forward 15mm (from what the plan specifies). I guess I could move the engine a bit more forward, but I don't know how it will affect the flying characteristics.

I have added 280g in front and my CG is about 140mm from LE (not so sure as I use the thumb method for balancing).
If I had a Saito 150 instead that is 10g heavier, it would not make much difference as I still would need 270g in front.

I guess what Juvaknin say that there is some difference of the fuselage weight (and balance) in each delivered kit may be a reason why we all get different CGs.

/Erland.

juvaknin

Yep, as i know almost every kit have diffrent weight....... (and not only on the YAK-54 Kits....)

ropowell

Juvaknin & Falcon26,

Here's some additional info as requested. Yes, the AC weighs in at 13.5 pounds ready to fly except for fuel. Also, I was incorrect in saying that I didn't add weight for balancing. I forgot that to move the engine forward, I added a 4" x 4" x 1" block of plywood in front of the supplied plywood block with some small standoffs to get downthrust and right thrust. I used some heavy screws for securing this so I really did add weight! I also used a piece of 1/4 " plywood (about 10 sq in in plan) to mount the radio batteries alongside the engine so this too added a bit of weight.

As for the fit of the cowl, I mounted the engine horizontally and the cylinder cutout is just behind the front radius of the cowl. The rear of the spinner ring is about 3/4 " from the front of the cowl and actually looks quite similar to the full scale YAK. I'll send some pictures later.

Most everything else is rather standard except that I modified the use of alighnment pins for both the stab and the wing. Instead of the supplied pins, I used 5/32 in. wood dowels for the wing and a 1/4 in. dowel for the stab. I also eliminated the springs by using an additional drawup bolt. I have two elevator servos installed as per plans and a single rudder servo with a pull-pull system.

I was supposed to fly this morning but while checking out the AC, I discovered that my rudder servo had stripped a gear (one shouldn't bang the rudder on doorframes!) so I didn't go. I'll let you know when I'm back in the air.

If I missed any questions, let me know.

juvaknin

ropowell, yes you forgot to tell us you will add Video!!
if you can, upload video... (i'll will upload video, but i have time to fly only mabe next week... so it will take some time...)

erland

Just weighed my Yak.
It weights 6.2 kg which according to excellent unit converters on the net gives almost 13.7 lbs.
This is including my extra 280g (.62lbs) in front.

So it seems pretty OK.

/Erland.

juvaknin

so it's looks like i have the heavy Yak-54 there is.......

erland

My guess is that Sonnich is heavier as he has a gasser in his.....

juvaknin

erland, you made your test flight yet??

SJN

Mine is the heaviest!

It weighs 7,1kg or 15.6 lbs

But, that is with several repairs because of the engine quiting in flight, and having to land in rough terain.
I think I have added about 200-400g of epoxy and cloth

juvaknin

i'm not pround on it, but sorry SJN "Mine is the heaviest"!! 7.5 Kg!!!
if i'll have time, i'll try to move my engine arround 18mm to front.. and then i'll be able to remove some weights i used.....