skysfallin

My Feedback: (10)

Slow and Steady, I have a brand new 120AX that has not been run yet . I am going to the field tonight after work ( thursday) to run some fuel through it and hpoefully get it in the air. With some of the people talking about vibration issues I hope the Dubro ISO mounts will help keep this under control. The 91FX with solid mounts that I had in the plane had very little vibration and I was hoping the 120 would be the same. Im going to breakin with a 15x10 APC prop and then play with some other pitches later. I dont think I should have a heat problem now as my cowl has a fairly large hole in it from changing the engines and mufflers. I have a Pitts style Bison muffler on both engine. I like the way they sound and you can keep the muffler in the cowl. I have since bought another cowl from Horizon and will fit it to this engine after all the testing is done. I'll let you know tomorrow how it turned out. Gary

skysfallin

My Feedback: (10)

Slow and Steady, I ran some fuel through the engine last night and got in two flights. I have to say the Dubro ISOmounts are a hit with me. The difference between the 91 and the 120 is noticeable but not anything to be concerned over. Dubro says to add a couple drops of fuel to the bushings to make them more pliable which should let the engine move more and cancel out even more vibration. I installed mine dry but will add some fuel tonight and fly on saturday and see if it makes a difference. As far as heat goes I did not notice any indication of the engine over heating but there again I have a rather large hole in the bottom of my cowl because of the engine and muffler change. Even with the Pitts style muffler you have to cut about a 2x2 inch hole to get the cowl on far enough to get over the pipes, so I think that should be a large enough outlet hole to remove heat, and I am also running a bit on the rich side right now. I am always impressed how well OS engines run right out of the box. The power difference between the two is very impressive. I still have to change the thrust angle but its coming along. I first thought this plane was a challange but now its an obcession. Gary

Slow and Steady

Gary, The word obsession was not what came to my mind, but I can understand, since the plane continues to fly better and better. My only issue now is the lack of power from the 91 FX. I look forward to your experience with the 120 AX. I am toying with the idea of investing in a Saito 125, which I saw once in this plane and it seamed to give the pilot alot of authority. Thanks for the info and good luck!

colin g

has anyone purchased the new colour scheme seagull yak , and if so what set up used and flights made? any quality difference to blue and yellow version?.

skysfallin

My Feedback: (10)

Slow and Steady, while the 120 is not the most powerful engine you can put in this plane it does perform well and will hover and pull up out of a hover. I have no issues with overheating of the engine and I am using the Bison pitts style muffler, however as I said before the hole in the bottom of the cowl is about an inch and a half square. I should think this is plenty of opening to get the heat out. If you look inside my plane there are five battery trays having moved the battery that many times to get the balance to where this plane would be predictable in flight. I have about twenty five flights on it now and is pleasurable to fly at this point. In the beginning it was horrible. But now I have no lead in the plane and all is good. Now I can start pushing it harder and enjoying it even more. Gary

Slow and Steady

Thank you Skysfallen, My 91 with an APC 14 6 is flying much better, I think the engine may have finally broken in to peak performance. However, I just may have to change out to the 120 ax, using a pitts instead of the orignal muffler, which may have blocked airflow. Thanks again for your response.

Dave Bushong

TKG I have a Zenoah g20 and would like your input about the Seagull and the g20. Would you recommend this set up?

I have been flying a Goldberg Yak 67 with the g20 but I have heard from others that the g20 and the Seagull are a good match.

Dave

CAT POwer

My Feedback: (61)

Dave, where do you fly at ?
Manfred

Dave Bushong

Manfred,

I fly in Johnson City. We have a great club there. (TRI Cities = Johnson City, Kingsport, Bristol)

http://www.flyjcrc.com/

CAT POwer

My Feedback: (61)

Dave, I used to fly at the old Bristol club site.

Aerobatx

My Feedback: (1)

One of the best things you can use for strengthening landing gear are bicycle spokes.

Drill a hole down near the wheel pants on one gear leg, then cross over to the other leg near the fuse with the threaded portion, drill another hole and put a nut. Then do the same thing on the other gear leg.

flycolorado

Finally, I maidened mine today, the sitter called in sick and I had it ready to go (it gave me an excuse to take a day off work)! Flew well with the only problem being my CG, it's at 5 1/2", I think i'll change it to 6" it was porpousing pretty bad, way to sensitive to elevator input. The only trim needed was about 3 clicks of up elevator. I'm a little curious as to why it feels tail heavy in the air but once I got it back on the ground the elevator was noticably "up". I hope it's not an incidence thing. The motor is an SPE 26cc gasser I bought online from China (I know, boooo), I had a BCMA version on it when I first started posting on this forum but I ended up putting the one I bought from China on instead (ran much better out of the box). It's still breaking in and I've got it pretty rich still so my 16-8 is only turning 7000. I flew mostly at 1/2 throtle, simple circuits a few rolls to see if the wings would fall off Landing was longggg... due to a high idle but very very soft! Ground handing is terrible, I'm going to change the tail wheel (I've got the kind with springs) to give more solid control. I bought it for as a Sunday relaxing flyer with potential, I think it will work out nicely for me. I'll "Tweak-Fly-Report" when I get a chance.

Crewdog

Okay am I missing something on this one? You mention that you feel it's tail heavy and you want to move the balance point further AFT??

flycolorado

Yes, if I'm not mistaking that should make it more nose heavy. Right?

Crewdog

The center of gravity is not necessarily a fixed point; its location depends on the distribution of weight in the airplane. As variable load items are shifted or expended, there is a resultant shift in CG location. The pilot should realize that if the CG of an airplane is displaced too far forward on the longitudinal axis, a nose-heavy condition will result. Conversely, if the CG is displaced too far aft on the longitudinal axis, a tail-heavy condition will result. It is possible that an unfavorable location of the CG could produce such an unstable condition that the pilot could not control the airplane.

http://www.free-online-private-pilot...d_balance.html


Okay, the above is clip of the article as contained in the web address. It's an article on weight and balance as outlined for private pilot flying. The article is a good read, but does point out the issue at hand as quoted above. These priciples apply equally from full scale airplanes to our models.

As well if you have any other plans or instructional booklets laying around take a look. Especially one for a 3D type plane. Most will tell you to start with the CG father forward and work your way toward the rear of the envelope as you feel comfortable with the plane. Others will list measurements with the forward CG for beginners/sport flying and more aft CG's for experts/3D flying. I hope this helps?

Crewdog

Moving the balance forward may improve the smoothness
and arrow-like tracking, but it may then require more speed
for takeoff and make it more difficult to slow down for landing.
Moving the balance point aft makes the model more agile
with a lighter and snappier “feel� and often improves knife
edge capabilities.

This quote is from an Easy Sport construction manual. I'm not trying to beat you up on this one, just wanted to make sure I had my facts straight. Happy Flying.

CD

flycolorado

Sorry, I totaly miss stated myself you are right. I had the right train of thought it just de-railed while I was typing. Yes move the CG further forward by adding weight to the nose (ie the ignition batt) more like 5" from the leading edge. You may have saved my plane! (I hope I would have figured it out on the CG machine).

Thanks 

PS. I just turned 40 a couple of weeks ago, can I blame it on old age yet!

Crewdog

UUMMM let me think, NOT, lol. I'm ahead of you in the age department, but then aviation is what I do for a living. So when I read your post, it jumped off the page at me. I drew a couple of diagrams before I responded, as I wanted to make sure I was correct. Then when you came back the second time, I "went in search of" lol. (The ole adage of "get the book out"). At that point it was time to find "data" to back up my words.

In the end, I like you, am glad we have the issue straight and you didn't loose the plane because of an error in balancing. There are enough other gremlins that are there to get us, don't need to ad that one to the list.

Hope moving the CG forward helps you. I have mine about ready to fly with an OS 120 4 stroke. The last thing I have to check is the engine thrust line. From the posts of others here, this plane seems to be critical in reference to the engine offset. I'm not sure, but you may want to check that on your plane too? Seems like most are running at or close to zero degrees of up/down thrust offset.

Fly Safe,

CD

tkg

My Feedback: (1)

FWIW the Yak flys way different with out the cowl. Before you get to far into the first flights get the cowl on.

CAT POwer

My Feedback: (61)

flycolorado, did you balance the Yak with the cowl and spinner at 5.5" ...?.. then removed the cowl/spinner to run engine ... maiden the YAK .?..
That is 6+ oz weight missing up front and it changed the CG to @ 6.2" to 6.6" at wing core,

CAT Power

flycolorado

I did balance with cowl in place but no spinner (I have no plans on using one). I knew that taking off the cowl for first flight would remove a small amount of weight. I find it negligible compared to the amount of fuel I can cary and burn that will change the CG as I fly.

Tonight I threw it on the CG Machine to verify 5 1/2" CG and it was still right on. I even charged the batteries to add weight... That's a joke folks.

I will continue to fly without the cowl until I've gotten the motor completly broken in and I'm used to the motor's quirks as it's no fun to remove the cowl to adjust the needles. I've not implemented any of the cool ideas for needle valve adjustments yet. For now I'm ok with flying without the cowl.

I ended up moving my ignition bat to the front of the fire wall and still that only slightly improved my balance. Next I moved my reciever pack to the radio tray and that gave me about a 5 1/8" CG (5" with the cowl). I'm calling that good for the next flight.

My next inspection is with the incidence meter as I appear to have some slop in the wing bolts that allows me to install my wings slightly off the thrust line of the plane without careful attention (I could even favor one up and one down if I wanted to [X(]). My plane was missing the wing bolts so I simply used standard nylon wing bolts to hold the wing on. Are the "factory" bolts self centering (counter sunk)? I've noticed that more expensive kits come with dowels to align the wings and these kits do not. My plan is to see what moving the rear of the wing up or down and tightenting the bolts does to make the wings out of alignment with respect to the horizontal stab and finding the sweet spot. Anyone else who has noticed this please chime in to save me the time.

By the way, I've got my CG Machine set up to it's widest setting so it is an inch or so away from the fuse and this will change my reading from those who are taking it where the wings meet the fuse. I'm used to doing it that way so im comfortable with it. I also don't trust the wing stipes as they can ba applied differently from kit to kit.

Thanks for the help...

CAT POwer

My Feedback: (61)

flycolorado, I got a 10oz tank right under the the wing tube .......there of my thinking with the cowl/weight... sorry.
CAT Power

flycolorado

No problem, I bought a gas tank made for boat and tried that as well but I didn't like the way it came out so I used the factory tank up front.

CAT POwer

My Feedback: (61)

flycolorado, I checked the incidence angle on 2 Seagull Yak's and both are 0.0 wing to elevator and 2deg neg (down) on engine.
Also a tail heavy plane would most likely need down elevator to keep the nose down ...you are up on elevator .. nose heavy ???...Incidence angle off ???
Also in 1 of the pic's you have posted it shows your rec. battery close to the rudder servo, mine is where Bill has his Page20 this thread.

Ohh btw I been building my Yak almost as long as you .... that going to "work" thing and the never ending "honey do list" keep getting in the way....lol

CAT Power

flycolorado

Flew a couple times today and it seems to be much better. I only moved the ignition bat to the front and left the reciever batt in its current location. Biggest difference was Ihad too much throw on the elevator and needed some expo. Ihave one last issue that I need help with though. It seems to be stuck to the gound on take off. I'll get it going to what seems more than fast enouph to rotate and it just won't then suddenly it will pop off the graound (of course by now I've got full up elevator). The only time I've ever seen this is on tricycle gear planes with the wing incidence negative. I'm pretty sure I was flying the tail when Itried to rotate but I cant remember for sure. Other than that it was a great day! By the way, the CG is still close to 5.5". The SPE 26CC is slowly starting to develop more power, I've still notpeakedit out yet though.

By the way CATPOwer, I checked the incidence as well and it's 0. I have no down thrust in the motor though, it's bolted flat to the firewall.