how to modify a tutor 40 wing for twin engines

[snakeyme 0]

i knows theres multiple threads from me on this, but alot of members seems to be wondering how im going to do this conversion.

So ive started this thread to explain exactly how im going to do this and be pre-warned this post is going to be huge!

 

Firstly, the preparation;

im gunna mark on the underside of the wing the exact location of the fuselage.

Then deciding what size your engines are going to be (im using 40's), find the propeller size and measure the distance from the tip of 1 blade to the centre of the propeller (ill be using an 11" diameter prop), then add 2" to this measurements (again as my prop is 11", half of this is 5.5" + 2" = 7.5").

Using the above measurement, measure the distance from the fuselage markings as this will be my prop center point and that is also where the center of the engine needs to be, mark this point on the underside of the wing on both sides.

Using a normal engine mount for the size of engines, measure the width of these mounts, work out the dead center of the mount and mark this on the wing (starting from the prop center point mark outwards) and make sure that these marking go from leading to trailing edges of the wing.

Cut 5mm wider than these markings to open up a hole in the wing.

Then u will need to measure the hight of the engine from tip of the glow plug to the absolute bottom.

Using a stiff ruler, measure up the wing thickness against the engines hight.

Find out what 1/3 of the hight of the engine is (from top to bottom) and this is where you want the bottom edge of the wing to be.

 

Second, the engine mounting;

Using the previously measured mounting, build a box around this mounting using ply wood to start with and then once this box has been built, use box balsa strips and glue/bond them to the corners of the box, making the balsa longer than the engine is high.

gentley break the joint between the left wing and right wing.

get some carbon or alu rods or tubes.

using the same size drill bit as the outer diameter of the tube or rod to be used, drill a hole through the wings d sections making sure u go through atleast 2 d sections past the engine locations and through the engine boxes.

place the engines into the boxes and secure in place using nuts and bolts.

Place very long lengths of fuel tubing to the carb and silencer (can cut to length later on).

Finish building a strong box around each engine making sure there are holes for fuel tubes, the exhaust outlet, (you may need to fit a pipe to the carb leading to outside the box for clean air to get into the engines) and of course for cool air to circulate around the engine during flight.

Shape this box to any shape u wish but taking aerodynamics into account.

You have 2 choices here, you can either fibre glass or sand the wood smooth on the engine cowlings (the boxes you previously made) and paint to desired colour.

Lift the cowlings into the wings and thread the rods/rods through the wings (forgot to mention that these need to be long enough to go through both left and right wings) and dry join the 2 wing sides back into place.

If your happy with the way the wings join, epoxy the joint and leave to dry.

 

There you go, 2 engines mounted on a tutor 40 wing, well in theory anyway.

[arun 0]

This is an extremely courageous project! I'm watching with interest as you make it sound so simple It wasn't clear where you were going to put the fuel tanks, are they going in the wing?

[snakeyme 0]

i have 2 choices with the fuel tanks, i can either mount them in the fuse and relocate the servos or as you said, in the wings.

 

To fit the tanks into wings is fairly simple,

Choose ur size of tank,

Cut a hole to size of tank,

Build a wooden cage around the tank,

Epoxy cage into the wing (best placed between wing and fuse).

If needed, build a hollow bulbous shape compartment on the underneath of the wing for extra room.

[snakeyme 0]

forgot to mention the 2 main principles of flying rc models;

 

1.) Center of Gravity, make sure that doing this does not affect this and the balance of the plane as if it does, the plane wont fly reliably and if it has affected the CofG, then rebalance this by adding weight where needed.

 

2.) aerodynamics, this is also very inportant as aerodynamics is the phrase given to how air passes around, over and below the plane to enable flight, make sure that all structural work/changes are smooth and aerodynamic.

 

There is a simple way to test your aerodynamics which ill explain below.

Get a small hand held fan (or similar device that pushes air),

Next you will need either smoke (or steam) or something like fine dust (crush some pencil centers and place in a shall dish),

Put the fan infront of the smoke or dust with the plane behind it,

Switch the fan on to see how the smoke/steam/dust flows over the plane and if u can, use a high speed camera to record it so u can review the footage afterwards.

[snakeyme 0]

just an update guys, ive started the work and have put the markings in place and have cut the holes in the wing.

 

I have taken pics of the progress so is there anyone i can email them to who can put them on here.