Airframe Suggestions for Saito FA-125a 4-Stroke

[Futura57]

I’ve just acquired a boxed unrun Saito FA125a 4-stroke for a very, very good price. Now I need to decide what to do with it. I know, I know, I couldn’t help myself.

 

I’m thinking a scale mono-plane, maybe a WW2 warbird. I’ve never had a decent sized one before, so now is my chance. But it could equally be a civilian aircraft, I honestly don't have a strong preference at this stage. I'm hoping I will know the right design when I see it.  My first thought was a Brian Taylor or Dennis Bryant warbird plan, but they seem to be around the 60-inch wingspan mark for 60 2-strokes or 90 4-strokes. I reckon the Saito 125 is really a step too far for these, so I’m looking for something a little bigger. I would consider scratch building from a plan, plan + wood pack, or a full boxed kit. I’ll even keep a look out for a second-hand airframe, perhaps even a decent ARTF. Probably with retracts too. I’m not necessarily looking to achieve a super scale finish. A good stand-off scale design would be fine. Slab sided or stringers I don’t mind. Ultimately, I’m open to suggestions. But it must be a practical flying model for bumpy grass take-offs and landings. If my choices are few then scaling an existing plan wouldn’t be out of the question.

 

I’m not likely to start this project until late 2024, so I’m in no rush to decide. If you have any suggestions, I’d like to hear them, ideally with a link so I can check out the specifications. Thanking you in advance.

 

 

 

 

Edited December 28, 2023 by Futura57

[David Ovenden]

I have a saito 125 in a Seagull Chipmunk.  It flys beautifully   its not a warbird but was used by the military. No retracts but it does have flaps and landing lights

Edited December 28, 2023 by David Ovenden

[Jon H]

The just shy of 70 inch brian taylor models would fly fine with the 125 on a 15x8. There's a Spitfire, Hurricane, P51 and Bf109e to choose from. Personally i am not a fan of the BT models. Although they look great and fly well they are extremely old designs now and require substantial reworking to be viable. They are also very lightly built and will not withstand the rigors of week in/out club flying. 

 

120 class engines sit in a strange place as they are a bit big for the 60 ish inch warbird and a bit small for the 70+ warbird unless they are light. 

 

On the artf front the seagull/escale seafire is nice. A clubmate has one and it looks great in the air. Its more scale in looks and performance than many of the ARTF offerings. The 63 inch seagull P47 would be a good choice too and i think they even offer the P47 as a kit these days. A number of customers are flying them on Laser 100's with no bother, so your 125 will be plenty. P47's are not the prettiest of models but if you are looking for an intro warbird  with a full house of gear/flaps they are excellent. Large fuselage for getting all the gear in, wide track undercarriage with big wheels, nice fat wing, large flaps and generally very stable as WWI fighters go. I recommend them to everyone i come across looking for a first warbird. 

[Don Fry]

Balsa USA Cub. Very nice flyer. Might even have one, NIB, for sale. Very good price. I’m going to be dead before I build my stash.

Edited December 28, 2023 by Don Fry
Honesty

[Futura57]

51 minutes ago, Don Fry said:

Balsa USA Cub. Very nice flyer. Might even have one, NIB, for sale. Very good price. I’m going to be dead before I build my stash.

 Hmm. I presume you are referring to the 1/4 scale J3 cub? On the face of it, possibly a bit too pedestrian for me. But never say never. At the moment I am liking some of the Seagull ARTF offerings as suggested. But it's early days so I will sit back and see what other recommendations come in. In the meantime feel free to PM me with some details. I am a sucker for a bargain 😉 Or you could put me in your Will 🤣

[Frank Skilbeck]

You could always build it as the clipped wing version.

[Paul De Tourtoulon]

17 hours ago, Jon - Laser Engines said:

On the artf front the seagull/escale seafire is nice

No too much power, mine has a Saito 100 in it and that's perfect.

 

If you are looking for an ARTF warbird go for a 20cc petrol one, like the ME 109, P 47, P 40.

[Futura57]

The Messerschmitt Bf109 is appealing except perhaps for the narrow undercarriage. But I do have over 50 years experience 🤔

[Paul De Tourtoulon]

1 hour ago, Futura57 said:

The Messerschmitt Bf109 is appealing except perhaps for the narrow undercarriage. But I do have over 50 years experience 🤔

33 cm apart on the Seagull one, maybe you just haven't mastered landing 'yet',,, 😂

[Low pass Pete]

How about a Seagull Christen Eagle.  Mine flew well on an OS 120FS so a Saito 125 would be perfect.  Would consider selling my airframe as the engine is now in a Seagull Chipmunk which is also fantastic.

[Paul De Tourtoulon]

Or the Black horse Pitts, mine has the 120 in it.

[Futura57]

On 28/12/2023 at 15:32, Futura57 said:

I’ve just acquired a boxed unrun Saito FA125a 4-stroke for a very, very good price. Now I need to decide what to do with it. I know, I know, I couldn’t help myself.

 

I’m thinking a scale mono-plane, maybe a WW2 warbird....

 

 

Alas, the Eagle and Pitts and are not monoplanes, which is what I am looking for. I have the Eflite Ultimate 3D biplane and I really don't like it that much. Interestingly, I've seen a fair few up for sale. I shall give mine one more season before letting it go. Biplanes are draggy and I don't go much for that style of flying which I find is heavily reliant on throttling. Perhaps it's because mine is electric. I know full well that large warbirds can bite, but I've flown enough of friends', and maidened a few, to not be intimidated by them, even with a narrow undercarriage - My take-off and landings are amongst the better ones at my clubs 😆

[Frank Skilbeck]

Was "sold" an old Seagull Christensen Eagle, a bit tatty with an old Kalt (re zenoah) 22cc petrol, it's an absolute delight to fly, probably nothing like a an Ultimate 3D biplane. The only real disadvantage over a monoplane is having to fit and remove 3 wings 😁 but they are fixed undercarriage so more tolerant of less than perfect flying strips.

[Futura57]

🤔This is tempting at £170

https://classifieds.bmfa.org/acadp_listings/sig-spacewalker-82inch

 

But may also be a bit pedestrian for me.

 

Edited December 31, 2023 by Futura57

[Futura57]

I've noticed a CM Pro Me109 up for sale on the BMFA Classifieds. 72-inch span for 2stroke 120-160 or 4stroke 140-180. Seems like a large engine recommendation for a six foot span model. Anyone know if my Saito 125 would be adequate? On paper it looks not. Thanks.

 

The Seagull offering at 64-inches span recommends a 4stroke 120, so I guess an extra 8 inches warrants a bigger engine on the CM Pro version. Maybe I've answered my own question 🤔 

Edited January 21 by Futura57
C.w. Seagull Bf109

[Jon H]

it will be fine if its not too heavy. And you can ignore most seagull engine recommendations as they really over do it. They recommend a 120 for their gipsy moth when they have flown successfully on engines far smaller. 

[Futura57]

6 hours ago, Jon - Laser Engines said:

it will be fine if its not too heavy. And you can ignore most seagull engine recommendations as they really over do it. They recommend a 120 for their gipsy moth when they have flown successfully on engines far smaller. 

@Jon - Laser Engines I've lifted the details below from the HobbyKing site. What do you think given the weight and wing loading? In old money I make that 33oz/sq ft (someone please double check) which I think for a larger model is not too bad. Do you concur? But is it on the lardy side for a Saito 125 to haul around?

 

Details;
Wingspan: 1850mm
Length: 1668mm
Weight: 5.8kg
Wing Loading: 103dm/2
Airfoil: NACA 2415
Wing Area: 56dm/2
Radio Req.: 5-7Ch (10 servo, standard size)

Engine: 160 2 stroke.

[Jon H]

i never work out my wing loadings so i have no idea. 13lbs for a 72 inch warbird isnt bad though and it will fly without doubt. You might lack a little grunt in the vertical, but it will loop with ease. There's a video on youtube of one with an fg20 saito and it looks like it goes alright. Another with a saito 150 which is very quick. 

 

The only thing to watch is the supplied spinner as they have been known to explode, so you may want to source an alternative. 

[Eric Robson]

I had a CML 109 with a Saito 125a and it flew very well, it would not go vertical but loops were better with diving to get the speed up. The undercarriage did not like our field and needed beefing up on the mountings. 

[Futura57]

Thanks guys. I just got a response back from the CM Pro Me109 seller on the BMFA Classifieds. He is adamant it needs a 160. So, on reflection, rather than risk £250 and a 150 mile round trip I shall keep a lookout for a second hand Seagull offering perhaps, at a good price 😁

Edited January 21 by Futura57

[Jon H]

5 hours ago, Futura57 said:

He is adamant it needs a 160

 

As he has never flown it how does he know? Also its not his problem after he sells it! 

 

I think i have told this story before, but its lost so ill tell it again. Some years ago a club mate had a Hangar 9 60 size F6f hellcat with a 90 4 stroke in it. It whizzed about alright, but he was struggling with it and asked my help. His complaint was a lack of power, and what should he do about it. New prop? Bigger engine? etc. So i took it for a fly and after a lap of the patch i said it didnt seem short of power. His response was 'but i cant even loop it, theres no power at all'. He was then shocked when i did a loop about 300ft in diameter. 

 

He was used to light sport models which respond to a 'bank and yank' flying style. This relative brick did not and his aggressive style did nothing but scrub speed by cranking large angles of attack on the wing. With the speed scrubbed off he lost vertical, which meant he lost potential energy on the way down, which he then recovered from hard and scrubbed more of his energy away. He was just too ham fisted with it. 

 

Preservation of energy is very important flying warbirds and its a skill many never seem to learn. Its a shame as a warbird flown with energy management in mind immediately looks more scale as its exactly what they do in the full size. 

 

I have also flown my flying test bench (85 inch brick of a model of about 20lbs) on everything from 120 to 450 glow and it was aerobatic on all of them. Sure it took a while to takeoff using the 120, but once up it was still perfectly able to loop. 

 

Still, if you arent sure then give it a miss by all means. 

[Futura57]

I do concur completely with your story @Jon - Laser Engines and I was a little taken aback by the seller's assertion. I've flown a few warbirds in my time and maidened them for others who have promptly put them in. I shall let the 109 go for now because the seller would not take an offer. Also, it is collection only. I reckon it could easily be around a couple more weeks. So, if I don't find anything else that yanks my chain I may well just pay the asking price. Then I need to make the 150 mile round trip and spend £25 on petrol to collect it.

[Paul De Tourtoulon]

16 hours ago, Futura57 said:

Wing Loading: 103dm/2

Nothing for that size of wing / plane, I always work out wing loadings, and in metric it's right up my street, I had a Leister model centre Hawk it was a small wing and I still remember it's frightening wing loading of 136g /dm2 it was fast but the swept back wing and it's profile made it a doddle to land.

 

Yes wing profiles and shapes do make a Difference.

[Futura57]

@Paul De Tourtoulon as a rule of thumb I've always believed that larger models are more tolerant of a higher wing loading. As you infer, more wing loading equals more airspeed to compensate. For smaller models with a high wing loading it can be a challenge to get them off the ground or hand launch them fast enough.

 

There is a question, of course, of the 109's 5.8kg weight (or mass, depending on your interest in physics 😉) and the consequential induced drag. In this regard, is the Saito 125 up to the job of hauling it around?

Edited January 22 by Futura57

[Paul De Tourtoulon]

I can't remember the proper numbers but it was around 30g dm2 for under 1 metre wing span 65g for 1.5m and 120g for 2m.

I just weighed my Seagull 109 with it's Rcgf 20cc petrol and

it comes in at 5.7 kilos and a wing loading of 116g/dm2

 

I personally think that it's a perfect match.