Saito 82B revs

[Brian Dorricott 1]

I have a Saito 82 in an old funfly ARTF I picked up at a show and it flies happily on 1/2 throttle doing everything it should but when I open the throttle wide open the engine revs increase but it doesn't go any quicker !  I must take off the spinner and look at the prop size , does anyone have any ideas as to why ? It's not a problem but would like to know the reason as feels a bit odd opening throttle and nothing changing except the engine revs .

[jrman]

Worth checking that the split collet on the prop shaft is not slipping or that the prop hub is not too thin and allowing the nut to bottom out before tightening the driver and collet sufficiently.

[Jon H]

does it have a master airscrew prop? is so that is your likely cause. That or its the wrong size prop for the model

[Gary Manuel]

If the engine revs increase, the prop must be turning faster. If there is no increase in speed, the prop blades must be flexing rather than pushing more air. Better prop or better speed measurement is all that is required.

[Martin Arnold 1]

Exactly which old fun fly model, most of these are best with fine pitch prop as you don't want to over speed the airframe.

[Denis Watkins]

So much to check Brian, as a Saito 82B has a lot of grunt, and could easily pull vertical on a funfly.

Check, looking down the throttle barrel that this fully opens as full stick is applied

As this could be partial, and the revs go up but nothing else.

Count the needle turns to fully in, the screw out fully

And clean the needle

Put it back, using your count

Start the motor and tune to full revs

Check the plug, is bright and shiny at the element

If it is grey, then change this.

[Martin Harris - Moderator]

Funfly, thick wing?  Maybe it's the airframe limiting the speed?

[Frank Skilbeck]

Have you measured the revs, it could be that the noise is changing but the revs aren't going up by very much. 

[Brian Dorricott 1]

Small update 

Can't find make other than its Funfly 90 with 60-90 2 stroke recommended . The Saito 82b is on 14x7 prop so in the range for the that . Gave it a little service and a new plug tightened prop etc . I'll give it go again tomorrow and see if it's any different.  Quite thick wings but very light construction with a long long fuselage and quite enormous control surfaces , don't mind admitting I have the rates dialled down to about 50% ( wimp).

[Brian Dorricott 1]

Sorry just noticed Jon's question its Graupner Sonic G or G Sonic 14x7 in.

[Denis Watkins]

36 minutes ago, Brian Dorricott 1 said:

Sorry just noticed Jon's question its Graupner Sonic G or G Sonic 14x7 in.

 

14 x 6 is likely not to overload this motor

Am trying to say 14 x 7 is overloading this, and  13 x 6 would more likely make the model a funfly

[Martin Arnold 1]

Hahaha, what a coincidence !! By shear luck I have been  actually flying mine today !! It's a YT International Magic 90 Funfly, bit like a Cougar 2000 on steroids.

 

A 14x7 on a funfly is all wrong anyway, you don't want to overspeed them..... It's all about grunt.

 

Mine is powered by a Saito 115 with an APC 16x4W prop, It is going to be very marginal with an 82 and the best prop for that on a funfly is probably a 13or14x4w.

 

I just don't think the 82 has enough grunt for that plane, used to have a Saito 91 in mine but it was a bit marginal pulling out of the prop hang, hence the 115 which is brilliant, the motor is giving 18.12lbs of static thrust at 9700rpm and the model is 6lbs 12oz all up.

 

The photos were taken by a club mate today !!!

Edited May 30, 2021 by Martin Arnold 1

[Martin Arnold 1]

Remember this is a large funfly at 6ilb 12oz with 62in span and 19in cord, giving 8.18 square feet wing area !!

 

To put it in perspective I have a Saito 82  APC 13x4W prop, in an old Irvine Wild Card wich is 4lb 5oz 52in span and 15 inch cord giving 5.41 square feet wing area.

 

 

 

 

 

[Brian Dorricott 1]

Thanks for replies I think I need to reduce the prop a little and if not rethink the engine setup . Might keep the Saito in meantime until I get used to flying it . What's a nice petrol for that do you think ?

[Martin Arnold 1]

9 minutes ago, Brian Dorricott 1 said:

Thanks for replies I think I need to reduce the prop a little and if not rethink the engine setup . Might keep the Saito in meantime until I get used to flying it . What's a nice petrol for that do you think ?

The Saito 82 is an excellent motor, just think it's not big enough for the Magic 90, yes it will fly it, but not with the sort of authority the model deserves.

Not into petrols myself, so not sure on that one, currently run all four stroke glow about 17 or so Saitos with the odd OS and YS.

Have to say it really tickled me when I came back from flying my Magic 90 and looked at your post, I was only saying at the field the that they were "Unobtainium" !! And there's yours, so there are at least two still alive !!

[Brian Dorricott 1]

Martin lve not seen another Magic Funfly , found it at Weston Park 2 years ago right at back of one the traders tents complete with a receipt inside going back about 18 years . That puts it about 20 years since they were current ?

[Martin Arnold 1]

Yes Brian you're not far out there, acquired mine in the early 2000's from a club mate who used it as a test bed for a Saito twin, can't remember which one.

The were sold by YT International in Walsall West Midlands, who used to do a very good range of ARTF models back in those days, Had a Gee Bee Racer off them with a Saito 180..... But that is a complete other story.