I just fininshed building a Sig Four Star 40 with a Saito 56 mounted on a anti vibration Dubro aluminum motor mount , and a 6 oz tank. The plane balances just ever so slightly nose heavy with the rx battery 4 inches aft of the T.E. and 1.5 oz of lead in the tail . I took it up yesterday for the maiden flight and it was very,very nose heavy .I trimmed in all the up elevator that I could but it still would not fly any where close to level flight . I cut the flight short and was'nt pleased with the way it handled . Should I adjust my elevator throw to get more up trim or will this just make flying harder when the fuel gets low ? The motor mount really puts the engine out front which I know adds to the nose heavy problem . Should I try a fiberglass motor mount which is a little lighter and would allow the Saito to be moved aft 1/4 to 3/8 inches ? Is there a remedy for this ?

Change mounts, as you are thinking and see what happens.

I, too would change the mount. Dave Brown makes a nice one that works well with the 4-Star.

I think your problem is not all engine mount, though. You stated it "balanced ever so slightly nose heavy" but was "very, very nose heavy" for the maiden. I think either your tailplane incidence is off, you have too much up thrust, or the balance is way, way off, if you put in all the available trim and it still flies nose down. I see guys at the field with .90's on their .40 size without having balance problems. I have that DuBro mount on one of my planes, works great for vibration, but it does stick the engine out there, especially a four stroke.

Yes with an empty fuel tank it balanced slightly nose heavy,3 inches from the LE in the middle of the wing spar . How do I check tail surface incedence and should I also Check the wing incedence ? To much up thrust can cause a nose heavy condition ? Still dripping behind the ears so all your suggestions are greatly appreciated .I hope to get the 4* problem fixed without augering in first , it seems like it will be fun to fly !

See if you can borrow an incidence meter and make all of the checks. Wing, stab and engine. Carefully recheck the CG, fuel tank empty. Make sure elev is at Zero with stick neutral. Make sure both ailerons are at neutral (not both up or both down). Check control throws again as well.

Try again. If the plane is in CG limits it won't matter if the engine is at the firewall or a foot in front of it. Well OK, it will a little but it will still be in balance.

Great , that gives me hope that I can fix the problem, will find or buy a meter and check it out ! Do you check incidence with the plane level in relation to the thrust line ? I guess if I buy one the instructions will tell me that ! Thanks again !

Just checking, you are balancing the airplane inverted as it is a low wing a/c. Are you using a spinner or a heavy spinner nut by some chance? I also put lighter dubro wheels on mine to lighten and move the the cg aft.

Yes the CG was checked with the plane inverted , aluminum spinner and light foam wheels . Yes, it's almost level,just slightly nose down at the middle of the wing spar 3 inches from the LE. I think I must have some how changed the tail or wing incidence or the eng. thrust . I used the aileron deflection gauge supplied with the kit so the ailerons are nuetral and the elevator was level with the stab . Maybe I had some epoxy under the stabilizer that caused a problem ,but I thouhgt I had it clamped tight . I think the meter idea will shed some light on it. Who makes a good incidence meter?

Get the great planes incidence meter and throw away the meter and zip tie a digital level on top of it... Its the best incidence meter there is. Extremely accurate...

The meter http://www2.towerhobbies.com/cgi-bin...&I=LXPW71&P=ML
The level http://www.sears.com/sr/javasr/produ...26+Protractors

I found Hanger 9's Angle pro Digital Throw/Incidence Meter for about sixty bucks it has a digital level and seems user friendly.I'll post what I find when the brown truck brings my meter.

If youve balanced good [with tank empty] then it sounds like a tail section problem. When you get your inc. meter , check the horizontal stab. Good luck!

While you're waiting for the BIG BROWN TRUCK, take a minute or two and try this......

Block your airplane up to sit level and solid. I do this on the garage's cement floor. I line up the fuselage to look level, but it works with the wing level too if the fuselage doesn't have some obvious "level" lines to it.

Take an accurate metal yardstick and measure all the incidences. It takes about 2-3 minutes to do. It costs zip unless you don't have a good metal yardstick or have to buy a house with a concrete garage floor.

Truth is, if you block the airplane so the wing is level, all the measurements are easier to read. But you then need to figure where to measure the fuselage. It's actually fairly intuitive to sort out what to do and where.

BTW, if you are a newbie, then you need to learn to eyeball a few things. Hold the airplane at the rudder and look squarely at the TE of the wing. Hold the airplane so that you're seeing half the wing above the ailerons and half the wing below the ailerons. You really should then only see the TE of the ailerons. If you see more of the top of an aileron than the bottom or anything like that, you need to adjust the aileron connecting rods.

What you're seeing your model do in flight can often be caused by having the ailerons rigged "both one way". It can happen from your connecting rods being off, or from warp in one or both ailerons, or warp in the wing. It can also happen when you bolt the wing on and it doesn't seat in the saddle flat. And you check that easiest by sighting down the model from the rear.

While you are checking incidences, check the engine to make sure it is not pointed down.

Well I checked the tail and wing incidence everything was fine, the problem was the engine thrust line was WAY OFF. I decided to go ahead and switch to a fiberglass engine mount . Hope to get back up this week . I will check all incidences on every plane before I get it in the air . Thanks everyone for the good suggestions on what to look for .

Was the firewall "way off"? You said that you "built" the plane so I assume this was a kit? If so, you now see the importance of attention to details.

Good luck. It should fly fine once you compensate. be sure you check side thrust too.

I know your not now...but for anyone else reading this, dont just "trim it" out...

I did that with my nexstar after a tiny crash that added some epoxy weight up front. I went out this weekend to fly it and just trimmed it back straight...which took alot of trim. Can you say "snap roll" at slow speeds...like 20 feet above the runway....it almost cost me my plane...after i added a little tail weight to balnce it dead on, a recentered the trim, and she flew beautiful again...

lesson learned...

Just back from flying my reworked 4 star 40 it flew GREAT ! I replaced the aluminum engine mount with a fiber glass mount and removed the aluminum spinner, which reduced the weight , and moved the Saito 56 aft 5/8 of an inch,rechecked c.g. , removed 1.5 oz tail wt. and moved rx batt. forward 5 ", plane balanced a touch nose heavy .Next I had to shimm the motor mount 3 degrees up, to get the 2 degrees down thrust that was built into the kit ? Love the 56 F.S., sounds great and plenty of power , flew for 10 min. only used 1/4 tank of fuel, it was a little to windy for me so I got her down and and just watched my hands shaking for 10 more min. What fun !