Hey everyone!

I'm building my 1st kit (4* 40) and everything is going well. However, I think I may be a little pickey when it comes to building this thing. For instance, with this kit, the engine mount has to be mounted to the firewall before it goes into the fuselage. I did this and am not happy with the way it turned out. The way I have it, the engine mount is about a 1/16 to 3/32 of an inch tilted to the right. Also, when mounted, the engine would be about an 1/8 of an inch below the thrust line that I had to draw on the firewall. I was thinking of making a new firewall out of 2 pieces of 1/8 ply epoxied together (like the plans say) and using a great planes adjustable engine mount instead of the 2 piece one provided by sig. Is this nessasary? Would the plane be o.k with the way I have it? Does the manufacturer build in room for "mistakes"? My feeling is that if I'm spending all of this time building this thing, I want it to fly right, not like a brick. Anyway, am I being too pickey? Should I just say the heck with it and see what happens? Or should I just go with my gut, take the extra time, and redo the firewall and engine mount? The problem is, that I'll probably find other things that I think aren't right and want to redo them too! When do I say "it's good enough"? Thanks

The only question I have is:

Did you drill the holes as the instructions told you to?

Sometimes engines are deliberatly offset to compensate for torque or other factors.

That's the bad part! The instructions just say to put the engine mount on without giving me a template or anything to drill to. They also show you how and where to draw the thrust lines but don't tell you why. I'm under the assumption that the engine shaft has to be centered where those 2 line intersect. That's part of my problem, I'm about an 1/8 of an inch below that line. Basicly, I eyeballed it. Has anyone else out there encountered this with a 4*? Is so, how did you deal with it? Thanks

Samsdad,
Don't worry about it! I havee not built a 4* but have built, bashed, and scratched a couple hundred models. The verticle displacement won't have a significant effect on flight. It may have a tiny effect on fuel draw due to the tank height relative to the spray bar. I interpreted your post to mean that the mount is rotated on the firewall compared to where it "should be." This is something that I do all the time to get the muffler where I want it to be.
Chuck

Thanks for the input Chuck. You did interperate my post correctly. The Mount is rotated on the firewal as compared to where it "should be". So, you're saying that it's ok that my engine will be lower (verticaly) than the drawn thrust line? That's good news. Should I still redo it to match the plans closer though? Thanks

As Chuck said, rotation doesn't matter at all. 1/8" difference on the fuel tank height may not matter either.

I wouldn't bother redoing it. If I did anything it would be adding a 1/8" shim between engine and mount. Something hard, but light, plastic or aircraft ply. If aircraft ply keep an eye on the bolt tightness if your not using lock nuts.

samsdad

The rotation will not upset anyhting and the 1/8" will not be noticable in flight. Suggest you finish the build and enjoy the flights. You're not building an ICBM that has to be in close critical tolerances. Build the plane as close to the plans as possible, but if the truth be known, it's more important to build straight and light. (within the weight recommendations)

it 's confussing when going from a trainner to a 4*
2% right thrust on trainners.
The 4 * has 2% down thrust built in I belive, but nothing mentioned
about right thrust.

How to mount or get the center line is on the plan.
I decided to add 2% right on my first 4*.
I also had the mount slightly off center to compensate for the centering of
the prop or spiner.
However, I ended up removing the right thrust
to make the plane trace truer. (added washers)

The 4* 40 is a great flier, wieght is a matter of taste to me.
The plane gets toss around pretty good in semi windy conditions.
I usually clip the wings 3-4" total and take out the diehedral and
it still floats

Depending on what engine/fuel tank you will be using , sometimes it'll
come out nose heavy. Posistioning the battery pack can be tricky
if you don't want to add lead to the tail.
I ended up mounting the pack in the cockpit and painting the canopy
to conseal it. This is after I've went with lighter wheels even.
If you have a flat battery pack you can plan ahead and mount
the servo tray a little bit forward. It will allow the pack to be mounted
aft of the tray under neath the rods.

if you're real pickie....
you'll notice the verticla stab is a just sitting on top of the horizontal stabs.
Not too healty if the plane decise to nose over on a landing on a dirt or grass field.
I added a tail a tail post and recutted the verticle stabilizer.
This way the fuselage is locking it in place like most other kits.
I also drilled tooth picks to the bottom of the verticle and have
extrude thur the horizontal into the tail piece.
I also added tri under the horizontal to stab.
The instructions will tell you to add tri ON TOP...which is not a pretty sight.
I also did away with the stock tail gear to relive stress to the rudder.

This will have more affect on the plane than the rotationing position of the engine
Be aware of the elevators. Makesure they're even.
Bend the rods to compensate before you glue.
The rod might be striagth.....but its the different angle that you drilled the holes for the rods.

I also had to notch #3 former , this will allow clearence for the airlerons torque
rods. You deffernently have to clip them.

I also leave the front bottom piece of the fuselage ungluded and make it a
hatch for the fuel tank and easy access to the bottom of the engine mount.
You never know when those engine mounts screws decide to get loose.
I usually use #8 machine screws with nylock nuts just to makesure.

It's also a good idea to put nylock nuts for the wheel axles.
It sucks to try to land without wheels.lol

I'm real pickie...
I mount a GP.40 extra 300 or .60 size landing gears on mine to give more clearance.
It saves me money on props later on.

If you're super pickie.
Those 1/4 balsa stock on the front part of the wing sucks.
I found myself many times having to cut film to reglue them back in place.
For some stupid reason , I'll pick up or grab the wing at that area.
The next 4* .40 will defferntly get some sprute or hardwood