Sam Longley Posted December 10, 2023 Author Share Posted December 10, 2023 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 1 Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted December 10, 2023 Share Posted December 10, 2023 Sounds like a very complex solution to a simple job. Chop the bearers off and use a proper mount. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted December 10, 2023 Share Posted December 10, 2023 Nylon mounts only need self tappers but your brass shim will work perfectly well. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted December 10, 2023 Share Posted December 10, 2023 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 Quote Link to comment Share on other sites More sharing options...
Peter Jenkins Posted December 10, 2023 Share Posted December 10, 2023 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. 2 1 Quote Link to comment Share on other sites More sharing options...
Peter Jenkins Posted December 10, 2023 Share Posted December 10, 2023 Sam, I've sent you a PM. Quote Link to comment Share on other sites More sharing options...
kc Posted December 10, 2023 Share Posted December 10, 2023 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. 1 Quote Link to comment Share on other sites More sharing options...
Sam Longley Posted December 11, 2023 Author Share Posted December 11, 2023 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 Quote Link to comment Share on other sites More sharing options...
Sam Longley Posted December 11, 2023 Author Share Posted December 11, 2023 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. Quote Link to comment Share on other sites More sharing options...
Peter Jenkins Posted December 11, 2023 Share Posted December 11, 2023 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. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted December 11, 2023 Share Posted December 11, 2023 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. 2 Quote Link to comment Share on other sites More sharing options...
Sam Longley Posted December 11, 2023 Author Share Posted December 11, 2023 (edited) 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 1 Quote Link to comment Share on other sites More sharing options...
Nigel R Posted December 11, 2023 Share Posted December 11, 2023 Must admit, 1/4 ply firewall at correct angle, plus glass nylon mount, seems like an answer without issues. 2 1 Quote Link to comment Share on other sites More sharing options...
Sam Longley Posted December 11, 2023 Author Share Posted December 11, 2023 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. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted December 11, 2023 Share Posted December 11, 2023 Fair enough Sam, your plane, your choice. If others think it suboptimal, that’s their choice as well. Quote Link to comment Share on other sites More sharing options...
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