I have recently built at Thunder Tiger Seamaster 40 plane to fly off my lake in Montana. I have had a couple of flights with it so far and have found that to fly the plane level I need to apply almost one half up elevator. I have moved the CG to the furthest back recommended location which seems to help a bit, but even when I am reducing throttle to come in for a landing I need to use a significant amount of up elevator to keep it level. I am using a OS 46fx and the battery is mounted behind the servo compartment.

Do I need to adjust the angle of the engine thrust as well, or should I continue to move the cg towards the rear? The plane was an ARF so I assumed that the stock thrust angle is correct.

I usually have a lot of spectators watching me (my previous float flying experiences were highly entertaining!) and the porpoising flying nature of this plane is not making me look to good!

Any insight would be appreciated.

I really don't think the C.G. is the main culprit. Check wing incidence, but I suspect it may be the incidence of the horizontal stabilizer. The leading edge sounds as if it may be positive to the thrust line. This would have the same effect as inputing some down elevator.
The following is from the Seamaster Assembly Manual. If you proceeded as outlined, the horizontal stab should be O.K. If not, it must be rectified.
"Mark the center on the bottom of the stabilizer at both the leading edge and trailing edge. Turn the fuselage over and block up the wing saddle so the top of the fin will rest on the bottom of the stabilizer. Make sure the wing saddle remains parallel with your work surface. The trailing edge of the fin should line up with the trailing edge of the stabilizer (hinge lines). Making sure the stabilizer is in proper alignment (use your center marks plus a triangle to make sure it is perpendicular to the fin), use a pencil to mark where the fin meets the stabilizer. Being very careful NOT to cut into the balsa wood, score and remove the covering material 1/16" inside your marks. Epoxy the stabilizer to the fin, maintaining proper alignment."

You can access the manual with this link:
http://www.modelflight.com.au/manuals/seamaster.pdf

Bob

My planes started to fly a lot better after I bought an incidence meter and began using it.

I use TWO incidence meters on mine, I found the the plane wants to turn to the side the meter in on if you use just one.

If it crashed after adding just one incidence meter, would you call that an INCIDENT or an ACCIDENT.

Bob

Thanks Bob. Is it possible that the fin was not shaped correctly? I assumed it would be cut and formed to the correct diminsions and would not have to be shimmed or reduced to get the stabilizer flat.
Assuming that the problem is as you suggest, how can I change the stabilizer incidence now that the plane is assembled?

Thanks,
Drew

The only answer is to remove the horizontal stabilizer and reposition it to the correct incidence (0-0). A little careful cutting with an Xacto should do it. If it can't be cut at the joint of the stabilizer you can measure below the stab a specific amount, say 1/2 inch, and place your cut at that point on both sides of the fuselage. When the stab is removed it will be easier to remove the remaining wood. The fuse can be repaired with another piece of wood and CA'd in place. It should be as good or better than the piece you removed.

Now you can reset the stab by sanding the replacement wood in place at the correct dimension.

Never assume everything on an ARF is at the correct settings. Always check before any final assembly because once you glue it, it's almost permanent until the Xacto or Zona saw comes out.

Basically what you are doing when putting together one of these models is Assembly and Rigging. It also occurs on full sized aircraft as well, when one is disassembled.

If this keeps up, I'm going to have to file an incidence report.

Incidently, how did the single incidence meter work out?

Bob

The SeaMaster is a "T" tail.....

You're right! Replace the word "fuselage" with "vertical stabilizer".

Bob

I have A Seamaster and love it. But mine is going to get some up thrust. From full throttle, timmed out, and cut power it starts to shoot to the sky.

I think I read that someone did this also

My CG is right at the mid point the book said

I had a minor crash in mine yesterday, my first time flying it. I'm pretty sure it got so much water in the fuselage that the CG was moving all over the place! I will go over all the possible leak points, and see if I can stop it from filling up again. It flies really well, but was pretty touchy, at least to me, having just moved from a trainer.

Mine does that also. However, it does it when I abruptly reduce the throttle from full to idle for landing. I soon determined that after the zoom, the trim was just right for approach speed. So, I just got to idle more slowly or when I drop the throttle quickly I apply some down elevator until it slows down. I too was going to put in a degree or so of upthrust but I would have to go to a lot of trouble if I kept the engined cowled. I just decided to live with it.

I have a Neptune (Seamaster knock off) and it behaved just like this. I found that I could eliminate it by mixing elevator with throttle with the computer radio CAP7 Futaba. Do you have a computer radio? I also added flaperons and find they a really nice for making very steep aproaches at slow airspeeds. I can descend at 45 degrees, power at idle, pullout at the last second, retract flaps and land in 15 ft. The water really slows the airplane fast.
Offgridman

Thats what I did put mix in and flying it that way for now... Im just getting use to it also .....but still love the plane!!

Think of the engine location, if you increase power the tendecy is to pull the nose down. When you trim for full power and you reduce power the tendency is to zoom. I'd think messing with the thrust line is where I'd start first. get that right and you may be suprised how much it effects your flying.

The engine is up on a pole trying to pull the nose down unlike one mounted to the nose. on the nose a little out of line will only effect it in some manuevers. On that pylon a little thrust line change is going to really change the trims with every power setting. I agree if you can mix the throttle with the elevator it should give some relief but try shimming the thrust line and see if that helps.


Pete