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Saito FA40a domed nut

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Brian Dorricott 112/11/2018 15:21:46
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Quick question Saito FA40a with wooden prop and a nice brass domed nut , does it need the supplied washer or just the domed nut ? Total brain fade here can't decide .

Alan Gorham_12/11/2018 15:32:12
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I'd be tempted not to use a wooden prop as they can often be lighter than composite types and a combination of the hub compressing over time and the high torque impulses when the engine fires can lead to the prop nut being kicked loose.

Brian Dorricott 112/11/2018 15:35:36
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Hi Alan only went with wooden because it's eventually going on Tiger Moth , any others that look right on a Moth ?

Jon - Laser Engines12/11/2018 15:36:59
4794 forum posts
179 photos

I would go without the washer if its got a shape to it. If its flat then leave it.

A wooden prop will not be a problem but Alan is right, you need to keep an eye on the prop nut. My saito 45 runs a wooden prop on my nieuport and i check the nut every now and then. Its rarely loose, but i do tend to go for it when tightening it up!

Alan Gorham_12/11/2018 15:52:29
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Observation of a club mate's struggle with an OS 48 Surpass a few years ago would suggest that a lightweight wooden prop on a single cylinder four-stroke with a decent power pulse can indeed be a problem and it's not nice ducking flying prop nuts in the pits!

Jon - Laser Engines12/11/2018 16:30:25
4794 forum posts
179 photos

the os 48 was notorious for throwing props. My dad got through almost a prop a week in the early days when it came out. I have an OS40 that will throw anything if you arent nice to it, and my enya 53 throws props if you dont warm it up before giving it full power. In most cases, its the engine that is the issue and not the prop.

In any case i use wooden props on all of my 4 strokes over 180 size as well as on the saito 45, saito 50 and a laser 70. None give any trouble.

The heavy brass prop nut will counter any loss of flywheel, using a larger prop will help as well. Something like a 13x5 or perhaps 14x4 or 5 will work nicely on the tiger as its not exactly a rocket ship!

cymaz12/11/2018 17:28:21
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8662 forum posts
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I tend to loosen nuts on wooden props when not in use and at the end of the flying day. The changes in humidity and temperature shrink and swell the wood....they may work loose if left done up.

Alan Gorham_12/11/2018 17:29:47
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957 forum posts
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It's a classic case of YMMV Jon.

I wouldn't fit a wooden prop on any of my smaller single cylinder 4 strokes after seeing what I have seen, plus I only hand start my engines and I like the flywheel effect a heavy glass prop gives.

I would/do use a wooden prop on my OS Gemini though.

Percy Verance12/11/2018 17:36:14
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Jon

Odd you saying the old 48fs was bad for throwing props? I had two of them back then (early 90's) and I can't ever recall them throwing a prop.......

Why so bothered about the appearance of the prop Brian? You can't see it when the model's flying....... wooden props are lovely to look at, but touch the ground even slightly and it's landfill. Even long grass can break them.. I once saw a bloke try one on a waterplane. It lasted about halfway into the take-off run before water spray shredded it.

 

 

Edited By Percy Verance on 12/11/2018 17:40:55

Jon - Laser Engines12/11/2018 18:17:35
4794 forum posts
179 photos
Posted by Alan Gorham_ on 12/11/2018 17:29:47:

It's a classic case of YMMV Jon.

I wouldn't fit a wooden prop on any of my smaller single cylinder 4 strokes after seeing what I have seen, plus I only hand start my engines and I like the flywheel effect a heavy glass prop gives.

I would/do use a wooden prop on my OS Gemini though.

im not sure what that is exactly so cant really comment. But i hand start all of my engines where possible. Its only the ones buried in cowlings that i leccy start. The wooden propped saito 45 is always hand started unless its freezing cold and i cant be bothered! Either way, my approach to wood props is simply to do it up tight and then leave the blasted thing alone. If there has been big change in temperature/humidity then fine, give the nut a tug and see what happens. Its really not a big issue though.

Percy, my dads first engine threw props all the time, the 2nd didnt. The engine was only replaced as the crankcase fell apart on the first. He suspected the early batches had something wrong but was never able to prove it. At the time others were having the same issue with the same engine, then it all went away.

Paul Marsh12/11/2018 19:29:39
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3706 forum posts
1053 photos

I would recommend to anyone using a four stroke, not to use wooden props for the reasons stated. The only times I tried doing so, each time, I had the prop smash itself to pieces when the throttle was advanced, even though set slightly rich, a nasty pinking sound just before the prop self-destructed, sending shards of wood everywhere.

So my advice: No wooden props, ever!smiley

Engine Doctor12/11/2018 19:34:55
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2300 forum posts
27 photos

As already said wooden props can compress then come undone and can be dangerous. Why not paint a composite prop totlook like wood for your Tigermoth ? I've done a few for scale models and they look very convincing .

Percy Verance12/11/2018 20:05:38
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8108 forum posts
155 photos

Hi again Jon

My first .48fs was an early one Jon, bought in 1990. The second I bought used a couple of years later. I used Model Technics castor based fuel (lots of it!) back then, always running ever so slightly rich. No dead sticks and never any other trouble. Nobody seemed bothered about the perils of castor or the advantages of synthetic fuels back then..... not that I remember much synthetic based fuel being around at that time. 

I never felt the OS 52fs ran as well as those first 48's, but maybe that was me......

 

Edited By Percy Verance on 12/11/2018 20:08:52

Jon - Laser Engines12/11/2018 20:21:11
4794 forum posts
179 photos
Posted by Paul Marsh on 12/11/2018 19:29:39:

I would recommend to anyone using a four stroke, not to use wooden props for the reasons stated. The only times I tried doing so, each time, I had the prop smash itself to pieces when the throttle was advanced, even though set slightly rich, a nasty pinking sound just before the prop self-destructed, sending shards of wood everywhere.

So my advice: No wooden props, ever!smiley

so why is it that none of my props have exploded?

Honestly posts like this really irritate me as they do nothing other than spread completely false information. Its nothing personal Paul, but this recommendation is complete nonsense.

There is a potential for wood props to be compressed and come loose but only if normal maintenance procedures are ignored.

Running rich will also not help and may in fact cause the prop to come off due to the engine not running smoothly.

You can all ignore me if you like, but as a manufacturer of 4 stroke engines im telling you wood props are fine if used correctly.

Paul Marsh13/11/2018 19:12:22
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3706 forum posts
1053 photos

Maybe on your Laser engines( i have 5 of them, one a V-twin), using a wooden prop isn't a problem. I've got over a thousand engines, and found that wooden props don't work well. On petrol, yes, fine, most two stroke, ok, maybe not totally suited, but am only saying what works for me.

Also, using a heavier wooden prop would help, but most I;ve ever got were very light. As for running rich, as you know, running a 4 stroke lean from new isn't the best idea...

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