I am modifying a glider and will be putting an engine in it. P-factor of course is an issue and although I do not know what the right amounts of right thrust to put in and down thrust for this model in the picture, I do know it for a similar model. My issue is how to properly measure how many degrees I currently have so I can make adjustments and wanted to see if anyone had methods they used to measure.

I can tell you what I have come up with, but wanted to see if there are better ones out there. An example of the engine mount Iam using is pictured below. Any particular ways I can accurately measure the true degrees that this firewall is set at in relation to the fuselage. Since the fuselage is not flat it is hard to have a right angle reference. I have been using a method where Irun a board flat against the area where the wings connect to the fuselage and then Iuse that as my right angle to measure the nose. Then I adjust the protractor until it sits flush against the whole face of the firewall. Then I check the measurement. That is currently how I do it. But new ideas are always welcome since that really only works ok for checking Yaw. The down thrust might require someother methods.
</p>

You could try one of these:

http://www.rcuniverse.com/magazine/a...rticle_id=1030

$219:00 !!

I bought a digital clinometer (spirit level with a display) from E-Bay a while ago. It measures in 10ths of a degree, with a zero-ing function. &pound;18
I have used it for incidence, thrust-lines and for optical measurements at work. I haven't used it for control throws because I think measurements of the linear surface deflection offer better resolution on larger models at least.
With a bit of setting-up of the centre-line, I reckon it would do a good job for this model.

Alternatively:
Attach a thin piece of stiff wire to the tail end to act as a pointer.
Support the model at the nose so that the pointer is close to the ground.
Use a spirit level to level the fiewall by moving the tail to the side. Mark on the floor, the end of the pointer.
Let the model hang so the centre line is vertical. Mark on the floor, the end of the pointer.
Measure the distance A between the marks.
Measure the distance B from the floor to the firewall.
The sidethrust angle is ARCTAN(A/B)
For a 3 degree sidethrust and a model with the nose 1M off the floor, the deflection would be 52.41mm, easily measurable to 1/2 mm.
At low angles like these, you could do direct scaling: 17.47mm per degree metre. ie 2 degrees = 34.94mm at 1M length or 69.88mm at 2 meters length

I didn't say it was cheap

Yeah I have to admit it is expensive.

Not sure I understand exactly what psuguru was saying. But appreciate the response. The meter seems like a good idea in the future.

tarrigo,

What you are doing is just fine.

Hang the fuselage only from several points in the tail, one at a time (plastic or wood cloth hanger clip and a piece of string will work).
Keep the hanger clip at that point from which the model hangs in a perfectly vertical attitude (visualize the cental line of the fuselaje), from a side view as well as from a top view.

Next, make a small hole at the point where all the lines converge in a school protractor.
Hang a plumb with a string that is tied to that hole.

With the fuselage still hanging, place the protractor against the firewall, in line with the horizontal tail.
The string of the protractor will indicate the side thrust built-in the firewall of the model of reference.
Then, rotate the protractor 90 degrees to be in line with the vertical fin.
This time, the string of the protractor will indicate the down thrust built-in the firewall of the model of reference.

Nothing is cheap anymore.. [&o]

Hey, did you ever find that dual ducted fan setup for the Diablo?


CGr.

Now you did it..

As beginners forum moderator, I may have to moderate this a bit.. we just can't have advanced math in a beginners forum... oops.. sorry..

CGr

4th form stuff, me old mate.
Or at least it was when I were at skewl.
'sprobably PhD level now.

Some models have zero right and zero down. Others may have three or more degrees. I do not know what is common for powered gliders.

Will you be using a cowl, or will the engine (or motor) be open?
If it's open, you can do this the easy way. Just use washers or other shims behind the mount to adjust the angle until it flies the way you like.

If using a cowl it's harder because you need the prop shaft to be in a certain spot.

Niether the amount of right thrust or down thrustis particularly critical. You can just eye ball it. As long as you can see that the motor is offset a skosh, you will be fine.