rgreen24

My Feedback: (6)

Anyone out there running this motor figured out the best way to add downthrust to a front punted motor? I need some more downthrust on my Spark and wanted to see if you guys had some tricks. By the way, I am using 4 bolts. Three on the bottom and one of the top.


Thanks in advance

patternflyer1

My Feedback: (11)

I use washers/spacers and learned through Jerry Budd, even aluminum cans as spacers if need be.

Edit: Or you could adjust your wings and stabs obviously.

Chris

VerneK

Robert,

If your front motor mount plate is glued into the fuse (solid mount), your options are limited. To add downthrust, you'll need to shim the motor away from the mount on one side. In your case, from the bottom. The easiest way is with washers. However, you'll need different thicknesses of washers unless you abandon the bolt closest to the bottom. If you stick with a bolt on the top, you could put a washer on each of the bottom bolts between the motor and the mount. It's not ideal, but that would cant the motor downward. If you stay with the mount pattern you currently have, you'll need the thickest washer on the bottom with slightly thinner washers on the two bolts above that. The top bolt will have no washer in either case.

I'm sure it's possible to mathematically figure out how much thicker the bottom washer needs to be than the two above it, but that's above my pay grade....

A secondary problem to all this is that the spinner at the bottom will be closer to the nose ring on the fuse than it currently is so you'll have to make sure it doesn't rub.

Hope this all makes sense.

Verne Koester

rgreen24

My Feedback: (6)

Thanks Verne and Chris

jgg215

Dont see why you have three bolts across the bottom and just one on the top. In the past I've used pieces from cheap feeler gauge sets to do the offsets. Makes it easy to increase or decrease the thrust setting.
John

Jetdesign

My Feedback: (8)

Some ideas I've had (I have a Pletti Advance) are shim washers, or a 'spacer' made of light wood to match the mount and sanded to the thrust angle.

I have been thinking of bolting my front mount to the plane so I could make adjustments there. If there are only two bolts (similar to the available mounts for the motor) there would be very little adjustment needed at the front of the plane, and a small adjustment to the rear mount.

Are you using a rear mount as well? Will take some adjustment there, too, if so.

rgreen24

My Feedback: (6)

I added a washer to each of the bolts on the bottom and got the desired downthrust I hopefully need. Will let you know how I works

wagen017

Any idea what downtrust that one washer has given you?

Volkert