Diamond Geezer Posted July 10, 2022 Share Posted July 10, 2022 Hi I have just changed the engine in my acrowot mk2 to an sc 61 now it’s quite nose heavy any idea how I can add weight to the back of the plane without it looking to unsightly.tia. Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted July 10, 2022 Share Posted July 10, 2022 How much extra weight do you need? Increase in engine weight x distance from COG to engine mount = distance COG to tail x weight required. Can you move the receiver battery back behind the COG? Quote Link to comment Share on other sites More sharing options...
Diamond Geezer Posted July 10, 2022 Author Share Posted July 10, 2022 Hi Shaun cant move battery or rx any further back and I need to add 100 grams. Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted July 10, 2022 Share Posted July 10, 2022 100g is around 9cc of lead so a cube 2.08x2.08x2.08 cm approx of lead or 3x2x1.5cm Can you cut a slot in the underside in front of the tail wheel and epoxy it in? Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted July 10, 2022 Share Posted July 10, 2022 (edited) Here's a bit of lateral thinking: Pour 100g of fine lead shot down the fuselage into the tail then inject superphatic glue into the fuselage with a syringe and needle, wait until its sets propping the fuselage upright. This is assuming that you used snakes for the control runs. Edited July 10, 2022 by Shaun Walsh Quote Link to comment Share on other sites More sharing options...
Diamond Geezer Posted July 10, 2022 Author Share Posted July 10, 2022 Great minds think alike thx Shaun👍🏽 Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted July 10, 2022 Share Posted July 10, 2022 I'm a little suspicious of the 100g figure; I believe an SC61 engine weighs about 600g with muffler, but what was the engine it replaced? The next size down, a 55, would weigh about 450 grammes without muffler (the only info I could find on the internet), so the engine weight difference you're trying to compensate for is maybe 100g, but if it's placed at the extreme rear of the aircraft much less will be needed due to the greater distance from the c of g. Having said that, if your 100g figure is the result of a physical check (e.g. a spanner temporarily taped onto the tail), you can safely ignore my comment 😃 1 Quote Link to comment Share on other sites More sharing options...
Diamond Geezer Posted July 26, 2022 Author Share Posted July 26, 2022 Hi all using the rule of thumb for cog one third of the of the wing chord which is 12” so at 4” 100grams of weight which I put in but then I searched for the cog on the web and it’s supposed to be 3.25”so then had to take it out again so the rule of thumb would have made my plane very tail heavy indeed. Quote Link to comment Share on other sites More sharing options...
kc Posted July 26, 2022 Share Posted July 26, 2022 Consider moving the elevator servo to the back with a very short pushrod for better control and getting weight further back. Perhaps move rudder servo and Rx battery too. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted July 27, 2022 Share Posted July 27, 2022 Make it too heavy and it will loose all its good flying characteristics and become a brick. 1 Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted July 27, 2022 Share Posted July 27, 2022 17 hours ago, Diamond Geezer said: Hi all using the rule of thumb for cog one third of the of the wing chord which is 12” so at 4” 100grams of weight which I put in but then I searched for the cog on the web and it’s supposed to be 3.25”so then had to take it out again so the rule of thumb would have made my plane very tail heavy indeed. cgCalc is very useful for working out the correct balance point. Quote Link to comment Share on other sites More sharing options...
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