Seagull Yak 54 and Saito 120R

[Martin Fraser]

Good morning folks,

 

I’ve just put this Seagull Yak 54 together having read Ross Clarckson’s excellent build thread of 2010 and can concur with his observations.

 

I’ve installed a Saito 120R radial in it, partly to run it in and to see how it performs and sounds as it was intended to drag the Fairy Swordfish about one day. I know it won’t sound like a 28L Bristol Pegasus 9 cylinder engine but if it’s too sporty I’ll have to rethink it.

 

It’s a nice fit within the cowling and with the RX battery up behind the fuel tank, the c of g balances 75mm back from the wing tip. I’m still waiting for an exhaust collector ring from Morris Mini Motors so that might add a bit more nose weight.

 

However, I’m a bit concerned about heat build up. The full size has a heavily louvred cowling so I might have to open up the moulded louvres in mine rather than hack great holes in it.

 

Cheers, Marty

[Jon H]

You need to fill in all of the gaps between the cylinders with baffles. This will improve the cooling significantly and reduce the exit area required. 

 

This is a photo of baffles installed on a full size radial engine

 

[Martin Fraser]

Wow, those baffles are really snug up against the cylinder fins. I'll have to devise something in thin alloy.

 

Thanks for the heads up Jon, Marty

[Jon H]

In the interest of simplicity i would glue balsa into the cowl so its all integral and minimises faffing about when you take the cowl on and off. 

 

This is the setup i used on my Laser 240v in my Hurricane. I filled in the gap in the V as well, i just dont have a photo of that. 

 

[Martin Fraser]

Very neat Jon, 

Thanks, Marty

[Frank Skilbeck]

You could ask MMM to ship you one.of These

[Martin Fraser]

Ah! good call Frank, I had forgotten these were available.

 

Many thanks, Marty

[Martin Fraser]

Hi All,

 

Still waiting for the exhaust collector ring so I'm pottering about with some small jobs on the Yak. Following on Jon's advice and Frank's post for a cowling baffle I've found some thin ply and knocked up my own which is a snug fit within cowl. 

 

We share our field with about 500 head of sheep and they don't half leave their calling card on the strip. Whatever they eat, it's fast setting and a nightmare to clean off!

I had to hose down the underside of the Fly Baby's wings last week. So with this in mind (I've not fitted the spats yet) but made some mudguards out of carbon fibre to try and keep the worst of the sheep sh1t off my new toy. 

 

Cheers, Marty

[Jon H]

Baffle looks great and will work well. If you want to get dead fancy you can glue images or 3d printed half cylinders in the gaps the real ones for cosmetic appeal. 

[Frank Skilbeck]

15 minutes ago, Jon - Laser Engines said:

Baffle looks great and will work well. If you want to get dead fancy you can glue images or 3d printed half cylinders in the gaps the real ones for cosmetic appeal. 

Or stick some bits of wood on to simulate some dummy cylinders, if you don't fancy cutting them Sarik do this wood pack. But at least paint them black.

[Martin Fraser]

Hi folks,

 

I've been doing a few ground runs on the Yak and trying to get a feel for the Saito radial. I've bit the bullet and installed a 3 pot onboard glow driver powered with a 1s 6000 mAh hard case lipo. My starting technique is to block the exhaust, cold crank with the starter until it sounds juicy and then heat the plugs. A few blips with the starter and it normally fires and ticks over.

 

As others have found, number 2 pot is a bit slow to join in from cold but once warmed up by 1 & 3 it runs well. See FLIR images at the end of the video. I've installed a temp probe on No1 cylinder head and have had a reading of 117*c after a good full bore 30second run. I've no idea if this is good, bad or ugly but as a precaution I've opened up the moulded in louvers on the cowling to provide a bit of through flow.  If it pulls this well once in the air I'll be very pleased but that isn't going to happen until the weather improves.

 

Cheers, Marty

P.S. I don't make a habit of standing in front of a revving engine.  

Edited February 7 by Martin Fraser

[Paul De Tourtoulon]

2 minutes ago, Martin Fraser said:

. I don't make a habit of standing in front of a revving engine.

Ok,  four strokes are renown for prop throwing, so you were in front to try and catch it ?.😜

[Jon H]

8 minutes ago, Paul De Tourtoulon said:

four strokes are renown for prop throwing

 

Are they? Not had any engine throw a prop on me since about 2007, and even then it was my fault!

 

Martin your engine sounds pretty good but i would take the time to make sure your slow run needle is as lean as possible. Do this with the glow support off. It will not cure the no2 issue, but it will help. I recently did some mods to a saito 170 radial and was able to make changes to the induction which improved the engine a fair amount. I also confirmed my suspicion that a geometry issue with the master/slave conrods causes each cylinder to have slightly different cam timing which is why they all run differently. I did have some other ideas for improvement, including an air bleed for the no2 cylinder, but it ran well enough and was totally reliable without glow support so i just left it alone. 

 

As for the cooling, i would leave it for now. The cooling will not work very efficiently on the ground as its lacking the slipstream it will see in the air. Once in the sky it should work much better. 

Edited February 7 by Jon - Laser Engines

[Paul De Tourtoulon]

1 hour ago, Jon - Laser Engines said:

Are they? Not had any engine throw a prop on me since about 2007, and even then it was my fault!

My Enya 90-4c throws props now and again, my OS 120 compressor all the time in summer, a  club members saito 100 all the time, till I put another thicker head gasket on it, this week another members OS 120 two days ago,  a four stroke only needs to be flooded when starting or a bit of dirt in the fuel line making the mixture to weak for it to throw one when at full throttle.

 

Take heed, Four strokes are renowned for throwing them, and some of the Saito Triples have fuel problems with different cylinders, there are plenty of videos on them, and also 'inlet kits' that seem to cure them, Google 'saito radial problems'.

[Martin Fraser]

3 hours ago, Jon - Laser Engines said:

 

Are they? Not had any engine throw a prop on me since about 2007, and even then it was my fault!

 

Martin your engine sounds pretty good but i would take the time to make sure your slow run needle is as lean as possible. Do this with the glow support off. It will not cure the no2 issue, but it will help. I recently did some mods to a saito 170 radial and was able to make changes to the induction which improved the engine a fair amount. I also confirmed my suspicion that a geometry issue with the master/slave conrods causes each cylinder to have slightly different cam timing which is why they all run differently. I did have some other ideas for improvement, including an air bleed for the no2 cylinder, but it ran well enough and was totally reliable without glow support so i just left it alone. 

 

As for the cooling, i would leave it for now. The cooling will not work very efficiently on the ground as its lacking the slipstream it will see in the air. Once in the sky it should work much better. 

 

Hi John, Yeah I'm sure there is a bit more room for improvement with both low and main jet tuning and also fuel choice. At the moment I'm running it on the same juice

(Opti 4st 15% nitro) I run my Saito FA -60T on but I've got some Prosynth 12% that I might try it on once I get it to the field.  

 

Thanks for your input, Marty

[Martin Fraser]

40 minutes ago, Paul De Tourtoulon said:

My Enya 90-4c throws props now and again, my OS 120 compressor all the time in summer, a  club members saito 100 all the time, till I put another thicker head gasket on it, this week another members OS 120 two days ago,  a four stroke only needs to be flooded when starting or a bit of dirt in the fuel line making the mixture to weak for it to throw one when at full throttle.

 

Take heed, Four strokes are renowned for throwing them, and some of the Saito Triples have fuel problems with different cylinders, there are plenty of videos on them, and also 'inlet kits' that seem to cure them, Google 'saito radial problems'.

 

Hi Paul, The only time I've had a prop throw its self was with my OS91 4c when I back flicked it with a chicken stick, probably prop nuts not torqued up quite enough. But point taken and I would never let anyone else in front of it while starting or running.

 

Cheers, Marty

[Jon H]

3 hours ago, Paul De Tourtoulon said:

My Enya 90-4c throws props now and again, my OS 120 compressor all the time in summer, a  club members saito 100 all the time, till I put another thicker head gasket on it, this week another members OS 120 two days ago,  a four stroke only needs to be flooded when starting or a bit of dirt in the fuel line making the mixture to weak for it to throw one when at full throttle.

 

Take heed, Four strokes are renowned for throwing them, and some of the Saito Triples have fuel problems with different cylinders, there are plenty of videos on them, and also 'inlet kits' that seem to cure them, Google 'saito radial problems'.

 

i dont think i can remember the last time i saw any engine at any club i have flown at throw a prop. 

 

Clearly you chaps are doing something wrong if you are throwing props that regularly. Like i said, i havent had one escape in probably 20 years or more and none of my engines have locknuts even. I do however keep an eye on my prop nuts being tight as many are wood and this can alter with conditions, but this is just normal maintenance.

 

A flooded engine may have its prop spun off by the starter, but that's your own fault for flooding it and it can happen to a 2 stroke just as easily (more so in fact). As for the dirt in the fuel line, why is your fuel dirty? Even so, the prop should not fly off as the engine will simply suffer a lean cut and stop. 

 

As for the saito inlet kits, one came with the 170 i was to working on and i didnt use it. The design was fundamentally flawed and would not do what it was advertised to do. It would have had a negative impact on the engine in a number of ways and i would not recommend them. Dont get me wrong, the saito effort is not spectacular either, but the so called upgrade is not well thought out at all. 

 

2 hours ago, Martin Fraser said:

(Opti 4st 15% nitro) I run my Saito FA -60T on but I've got some Prosynth 12% that I might try it on once I get it to the field.  

 

I dont care for either fuel but absolutely stick to the opti given the two fuels you have available. Going forward though i would try a lower nitro fuel and see how you get on. I ran the 170 on the 5/15 fuel i use in everything and it would idle happily just over 2000rpm without any glow support. I left it like that for a few minutes and it still throttled up on all 3 so i considered that a win. some years ago i had a 450r3 and ran it on 5 nitro with 15 synthetic and 2 castor (it was before i saw the light). I was able to match or exceed the performance of chaps in the US using 20 and 30% nitro and i didnt need the glow support they did to keep an idle. These radials are not that responsive to nitro so it will not offer the advantage it might in another type of engine. High nitro fuels demand a greater physical quantity of fuel in the engine and this cools the cylinders making a flame out more likely. The lower nitro fuel will allow the engine to remain hotter at idle and this will aid in keeping the glow plugs alight. As i have mentioned before i run my OS 4 cylinder using the 5/15 fuel and have not lost a cylinder on it in the 3 or 4 years i have been flying it, and my ASP 160 twin uses the same juice and gives no flame out problems either. 

 

 

 

[Ron Gray]

3 hours ago, Paul De Tourtoulon said:

Four strokes are renowned for throwing them

That is utter rubbish Paul, unless you are just referring to your club that is 🙃

[Paul De Tourtoulon]

10 hours ago, Ron Gray said:

That is utter rubbish Paul, unless you are just referring to your club that is 🙃

No, I have witnessed it for years, the first time around 1984 at a local club, it's president at the time with an OS .61, ( I even remember his name) maybe I see it a lot as I spend so much time flying, 4 afternoons since Saturday, with between 4 and 8 members flying four strokes, I used 3+ liters of fuel this week and used 20 + last year ( I do also have a lot of petrol engines ) and just ordered 25 liters of Methanol fuel.

 

Ron, I flew in most meetings in a 200-kilometer radius from my model shop from the 1990s till 2010, (mostly Helicopter demonstrations ) as the owner of a model shop I have seen a lot,,,also from 1984 when I was building and selling my own kits on the model fields.

 

 As for fuel, most 4 strokes will run happily on 7%/12% nitro, oil, I won't go into that, but if it's coming out of the exhaust there is enough.

 

I have flown Prosyntese 10% for years and mixed the 5% with the 10% to give 7.5% nitro. ( thanks David ) great stuff.

 

Ps, I forgot to mention that an OS 120 threw its prop in the air on a 2m P.51, Saturday, and luckily found in the grape vines, flown by a competent modeler who has an online model shop, after closing his one in Montpellier around 20 years ago, so not a beginner, I first met him in the late 70's when I was flying my Multiplex Filious on a Cox,,,

[Ron Gray]

That explains a lot Paul, but then, don’t you also like castor? Now if you had said that 'for me and my friends, 4 strokes have an annoying habit of throwing their props' then that would be fine, but a glib statement that infers all 4 strokes throw their props is, as I said, utter rubbish. 

Edited February 8 by Ron Gray

[Paul De Tourtoulon]

As said, 4 strokes do throw props, 'however', looking at the number of pilots and flights within the year it is a very small percentage,

I just worked out my 25 liters that I ordered and mixed together, maybe a bit too much Castor, but you can't have enough of a good thing,,,😂

9.6% nitro

12% synthetic oil

3.6% castor

 

Sorry Jon,,,

 

 Ps, 2 strokes and Petrol, 4/2 strokes don't seem to throw props.

Edited February 8 by Paul De Tourtoulon
Ps

[J D 8 - Moderator]

            Ever seen a 2stroke throw its prop and then go on as a shaft run? I have and scary stuff.  Most of us scarpered away including the owner but a cool headed member reached in from behind and pinched the fuel pipe shut.

[J D 8 - Moderator]

     I have a CL flying friend who never did his prop nuts tight enough I learned, so first thing to check on a model of his.  He just could not bring himself to lean on the nut enough.

 Even a 1/4 inch bolt/shaft can take a lot of torque that you will not exceed with the right size spanner in hand.

[Martin Fraser]

13 hours ago, Jon - Laser Engines said:

I dont care for either fuel but absolutely stick to the opti given the two fuels you have available.

 

That confirms my experience with Prosynth Jon. My LHS ran out of the Opti juice so I tried their 12% in the wee Saito 60 twin and it just didn't perform or sound the same despite retuning. I think that's why I've still got half a gallon of it left over.

 

Cheers, Marty

P.S. Snowing in Denbighshire today!

Edited February 8 by Martin Fraser

[Paul De Tourtoulon]

Sorry if I am going on, but I was talking to the club members this afternoon at the model field, they all

Confirmed the prop throwing on their 4 strokes, and reminded my why the most of them were supplied with a locknut,

 

 It's even in OS instructions,,

 

,Safety Propeller Locknut assembly prevents the propeller from being thrown - even if it becomes loose in operation. Particularly suitable for medium to larger four strokes and essential for engines that are prone to kicking the prop free due to a backfire.

 

 Reminds me of kick-starting old 4-stroke motorbikes.😨