DaveyP Posted January 22, 2018 Share Posted January 22, 2018 Hi All, I'm building an old Premier products 4ch. trainer called a Preceptor. It is 60" wingspan and will weigh around 1.5Kg (3 1/4lb) Max. The instructions recommend a Merco 30 - 40 but I have a similar sized trainer which weighs the same and has an Enya19, soooo, is this under powered or will the Preceptor be over powered ? p.s. I have an OS 25 in the draw would that be suitable ?Edited By DaveyP on 22/01/2018 12:28:49 Edited By DaveyP on 22/01/2018 12:47:39 Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted January 22, 2018 Share Posted January 22, 2018 I used to fly my Ben Buckle Super 60 on an OS25 FSR and it wasn't short of power. Quote Link to comment Share on other sites More sharing options...
Nigel R Posted January 22, 2018 Share Posted January 22, 2018 A .19 in a 3lb plane would be in principal be fine. However. If it's a really draggy airframe, you might want a bit more power. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted January 22, 2018 Share Posted January 22, 2018 I would be tempted, given that it is an aileron trainer,to go a bit bigger, say a 30 size motor. But the 25 would do the job. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted January 22, 2018 Share Posted January 22, 2018 I would agree that a .25 would be a good choice. You could go up to a .32 which would be a very useful motor for later aerobatic models Such as my CAP 21 etc Quote Link to comment Share on other sites More sharing options...
roger graves Posted January 22, 2018 Share Posted January 22, 2018 Whilst the power of modern motors is greater than the old tech no one has raised the question of weight. As it was designed for the Merco I would suggest a similar weight engine be used or be prepared for large lumps of church roof to be bolted up front. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted January 22, 2018 Share Posted January 22, 2018 So dispite the aweful weather, and flying withdrawal symptoms, we are not even arguing. A 25 or a 30. Your cheque book, your decision. Quote Link to comment Share on other sites More sharing options...
DaveyP Posted January 23, 2018 Author Share Posted January 23, 2018 Thanks for all the replies, as I already have the os 25 that's what i'll use. I've no idea what a Merco weighs so will have wait and see where the c of g is p.s. I've worked out the wing loading is 13.5oz/sq.ft Edited By DaveyP on 23/01/2018 08:58:14 Edited By DaveyP on 23/01/2018 09:03:33 Quote Link to comment Share on other sites More sharing options...
roger graves Posted January 23, 2018 Share Posted January 23, 2018 here http://www.windyurtnowski.com/DaveDay/merco/am35.htm Quote Link to comment Share on other sites More sharing options...
DaveyP Posted January 23, 2018 Author Share Posted January 23, 2018 Thanks Roger, The merco on it's own weighs roughly the same as the OS complete with carb and muffler Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted January 23, 2018 Share Posted January 23, 2018 You are spot on with your estimates and engine size Davey, and well within the margins. I mean by the margin of full and empty tank that we fly with. The Seagull Boomerang 25 is in your range, and heavier, yet fly's well on the 25 and from full to empty tank on the selected C of G. Go for it Quote Link to comment Share on other sites More sharing options...
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