Engine alignment

[Sam Longley]

On 09/12/2023 at 12:04, kc said:

There is a school of thought that says that side and downthrust are remnants of free flight and are not needed with RC.  Much easier if the motor has no down or sidethrust - cowl fits nicely etc.

I do not like the idea of using trim on the radio as this will vary on power output & will upset  trim for rolls in IMAC etc. The Avanti should be a well balanced plane if built correctly . Then i can play with trim as i like. I am not an advanced pilot, but I will get better with the right set up & gear to start with

[Martin McIntosh]

Sounds like a very complex solution to a simple job. Chop the bearers off and use a proper mount.

[Nigel R]

Nylon mounts only need self tappers but your brass shim will work perfectly well.

[Martin Harris - Moderator]

Sets of angled plastic shims used to be readily available from SLEC.
 

Worth a rake around if you have a LMS. 

 

https://www.slecuk.com/index.php?route=product/search&search=Thrust&category_id=0

[Peter Jenkins]

2 hours ago, Sam Longley said:

I do not like the idea of using trim on the radio as this will vary on power output & will upset  trim for rolls in IMAC etc. The Avanti should be a well balanced plane if built correctly . Then i can play with trim as i like. I am not an advanced pilot, but I will get better with the right set up & gear to start with

 

If you aim to fly precision aerobatics then you should understand that setting downthrust to exactly 1.5 deg is not the end of the story.  You then need to fly the aircraft to make sure that the downthrust is correct for your aircraft.  The chances are it won't be.

 

However, before you get there it is more important to set up the CG to its optimum position.  Any other trim adjustments then follow.  If you change the CG after you have made the other trim changes they will all then need to be re-done.  CG position is the single most powerful trimmimg tool at our disposal.

[Peter Jenkins]

Sam, I've sent you a PM.

[kc]

SLEC sell a set of  thrust wedges for engine mounts at £1.39 set   - a pretty good buy I reckon.       Much better than adjusting the firewall or engine bearers.

[Sam Longley]

12 hours ago, kc said:

SLEC sell a set of  thrust wedges for engine mounts at £1.39 set   - a pretty good buy I reckon.       Much better than adjusting the firewall or engine bearers.

Thanks for the link. Have ordered a couple of sets

[Sam Longley]

13 hours ago, Peter Jenkins said:

If you aim to fly precision aerobatics then you should understand that setting downthrust to exactly 1.5 deg is not the end of the story.  You then need to fly the aircraft to make sure that the downthrust is correct for your aircraft.  The chances are it won't be.

 

However, before you get there it is more important to set up the CG to its optimum position.  Any other trim adjustments then follow.  If you change the CG after you have made the other trim changes they will all then need to be re-done.  CG position is the single most powerful trimmimg tool at our disposal.

Re C of G people often forget to balance the wing tips as well. One ARF plane I bought needed a surprising amount out on the tip.

[Peter Jenkins]

1 hour ago, Sam Longley said:

Re C of G people often forget to balance the wing tips as well. One ARF plane I bought needed a surprising amount out on the tip.

You can make some adjustments when the aircraft is static but the only definitive way to check this is during flight testing and then finalusing any further adjustments.

[Martin McIntosh]

Shimming a mount is fine but adding  washers to engine lugs not only can distort the crankcase as I said above but the screws will no longer be at 90 deg and the heads will definitely shear off in time.

[Sam Longley]

2 hours ago, Martin McIntosh said:

Shimming a mount is fine but adding  washers to engine lugs not only can distort the crankcase as I said above but the screws will no longer be at 90 deg and the heads will definitely shear off in time.

Not if you put counter shims above the crankshaft plates to match tapered shims below the engine bearers

 

Edited December 11, 2023 by Sam Longley

[Nigel R]

Must admit, 1/4 ply firewall at correct angle, plus glass nylon mount, seems like an answer without issues.

[Sam Longley]

52 minutes ago, Nigel R said:

Must admit, 1/4 ply firewall at correct angle, plus glass nylon mount, seems like an answer without issues.

 

52 minutes ago, Nigel R said:

Must admit, 1/4 ply firewall at correct angle, plus glass nylon mount, seems like an answer without issues.

Problem is that it does not fit the design & it does not allow for changes in the downtrim of the engine without resorting to shims.

[Don Fry]

Fair enough Sam, your plane, your choice. If others think it suboptimal, that’s their choice as well.