Acro Wot XL Engine Choice

[Bob Cotsford]

Hmm, my AstroHog had an OS 46 FX which was plenty for the lightly loaded vintage model, and it balanced without any lead. When I had an AW XL with a 38cc 4 stroke petrol motor it was by no means overpowered, it's a different style of model for different expectations. The problem with big 2 strokes, whether petrol or methanol fueled, is the noise level. Hence a lot of owners opt for bigger, heavier 4 strokes, and as Paul said, why put a lighter motor in if you then need to add lead to balance the model?

[Richard Clark 2]

Posted by Bob Cotsford on 30/07/2020 15:54:59:

Hmm, my AstroHog had an OS 46 FX which was plenty for the lightly loaded vintage model, and it balanced without any lead. When I had an AW XL with a 38cc 4 stroke petrol motor it was by no means overpowered, it's a different style of model for different expectations. The problem with big 2 strokes, whether petrol or methanol fueled, is the noise level. Hence a lot of owners opt for bigger, heavier 4 strokes, and as Paul said, why put a lighter motor in if you then need to add lead to balance the model?

 

We can all attempt to justify our purchases. I was merely looking at it from a 'practical flying' point of view.

And as for quietness a four stroke twin has the same number of firings  as a two stroke single and is often unsilenced. I doubt the twins  are any quieter. That's why 'They' use noise meters. It avoids any subjectivism about sound frequency (eg two stroke singles vs four stroke singles) or 'more pleasant' . To non-modellers they all make a racket.

Edited By Richard Clark 2 on 30/07/2020 16:44:40

[Bob Cotsford]

I don't really think I need to justify my purchases to anyone . Dunno about 'they', I just got my models tested using the clubs calibrated meter and 4 strokes (even the Laser twin I used to own) always seem to come out quieter than equivalent power two strokes.

Maybe I'll just leave it at "different strokes for different folks"?

[Jon H]

Posted by Richard Clark 2 on 30/07/2020 15:21:45:

I think many people greatly overdo the power.

The Acro Wot XL is only six inches wingspan bigger, about two and a bit pounds heavier with the recommended large and heavy petrol engine and has a bit more wing area.

I think anything bigger than a 120 two stroke glow is totally unnecessary and largely accounts for the specified weight. Twins are even worse as even glow ones are usually pretty feeble for their size and weight. The lighter the plane the better it flies, particularly so with fully aerobatic planes.

Edited By Richard Clark 2 on 30/07/2020 15:30:52

I agree most over do the power in models but in this case the AWXL can take it.

Although its only a bit bigger on paper than an astro hog its twice the model in terms of bulk and it is (by class) an extra 300 where as the hog is an upside down piper cub. They just arent the same model.

The AWXL will fly on a 120, but it would be..pretty lacking overall. 180 4 stroke is always my recommendation for the model and while mine has that 40cc OS its also very heavy due to the weight of the engine and not all 40cc engines are created equal. The OS would easily loose a tug of war with a dle30.

In any case, when hooning around with a laser 180 powered example there was little between them in terms of overall performance.

[Stephen Smith 14]

My AWXL has ample power with its DLE40 twin

[Richard Clark 2]

Posted by Jon - Laser Engines on 30/07/2020 17:04:19:

Posted by Richard Clark 2 on 30/07/2020 15:21:45:

I think many people greatly overdo the power.

 

The Acro Wot XL is only six inches wingspan bigger, about two and a bit pounds heavier with the recommended large and heavy petrol engine and has a bit more wing area.

I think anything bigger than a 120 two stroke glow is totally unnecessary and largely accounts for the specified weight. Twins are even worse as even glow ones are usually pretty feeble for their size and weight. The lighter the plane the better it flies, particularly so with fully aerobatic planes.

Edited By Richard Clark 2 on 30/07/2020 15:30:52

I agree most over do the power in models but in this case the AWXL can take it.

Although its only a bit bigger on paper than an astro hog its twice the model in terms of bulk and it is (by class) an extra 300 where as the hog is an upside down piper cub. They just arent the same model.

The AWXL will fly on a 120, but it would be..pretty lacking overall. 180 4 stroke is always my recommendation for the model and while mine has that 40cc OS its also very heavy due to the weight of the engine and not all 40cc engines are created equal. The OS would easily loose a tug of war with a dle30.

In any case, when hooning around with a laser 180 powered example there was little between them in terms of overall performance.

 

The OS 40cc four stroke will easily be beaten by the DLE two stroke, as you say.

But equally the Laser 180 will be beaten by the OS 120 two stroke. The Saito 180 twin previously mentioned seems to be particularly light. But it's not very powerful for its size. Twins, be they two stroke or four stroke, usually fall down on internal friction, especially at these small sizes. And even single cylinder four strokes are at a disadvantage. The OS 91 two stroke is close to double the power of their 91 four stroke. The heli engines are even better, throttle very well, and they only need the head turned down (if you want it cowled), plus a prop driver. There's one in a 'classic' pattern plane of mine.

And as you also say the differences. won't be noticed much in the air.

Edited By Richard Clark 2 on 30/07/2020 20:08:39

[Richard Clark 2]

Posted by Bob Cotsford on 30/07/2020 16:58:03:

......Maybe I'll just leave it at "different strokes for different folks"?

I certainly agree with that.

But despite my first sentence mentioning what many people do my post was about the aircraft, not about people or "folks"

[Mike Sedge]

Just to add to the mix, I'm running on a DLE 40cc Twin and it works great, plenty of power and runs beautifully, will prop hang and knife edge without problems. A guy at my club said it would be overpowered but it seems a really good fit as far as I can tell.

[Tim Flyer]

I own and use an OS 120 AX two stroke as well as Laser 155 and Laser 180 4 strokes. The OS 120 ax is far weaker than my 180 4 stroke engines. I would say it compares closer to the Laser 155. My Acrowot XL uses a Laser 180. I prefer that to using my 155 in it .. I wouldn’t want the OS 120 AX in my Acrowot XL. It’s a model that can use power.  

Edited By Tim Flyer on 17/01/2021 19:07:30

[Richard Wills 2]

But equally the Laser 180 will be beaten by the OS 120 two stroke. The Saito 180 twin previously mentioned seems to be particularly light. But it's not very powerful for its size. Twins, be they two stroke or four stroke, usually fall down on internal friction, especially at these small sizes. And even single cylinder four strokes are at a disadvantage. The OS 91 two stroke is close to double the power of their 91 four stroke. The heli engines are even better, throttle very well, and they only need the head turned down (if you want it cowled), plus a prop driver. There's one in a 'classic' pattern plane of mine.

And as you also say the differences. won't be noticed much in the air.

Edited By Richard Clark 2 on 30/07/2020 20:08:39

The OS 91's will produce double the power of the 91 four stroke, only problem there is to get the hp you would need 15,000 rpm which means something like an 11x6 or 11x7 prop. Pretty useless thrust wise on anything larger than a 40 size aeroplane. On representative props 14" plus the difference is much less pronounced.

[Tim Flyer]

Well said Richard. I think Bobs comment is also very true . The engine is part of the balance of the plane and if it can be used instead of useless ballast that’s an excellent idea. My laser 180 perfectly offsets my tail mounted servos in my Acrowot XL, so I did not need any additional balancing weight. There are loads of good combinations and it would be dull if we all had the same

[Richard Wills 2]

It is a fantastic plane for loads of engines. I have swapped the 180 out of mine for a Moki 210 on a 19x10, now it has a fire lit under it. Loads of fun.

[Jon H]

Mine is lovely with the 240 pegasus. Its not fast..i mean its quick enough but not blistering, its not got unlimited vertical but its got enough. The thing that makes it though is the sound. 4 cylinders chattering away and the model is just so smooth and stable its a joy to fly. I dont thrash it, 5lbs of very long engine hanging off an artf firewall means i dont do any flick or snap type stuff, but for everything else its just a delight.

I will get a video of it at some point

[Rich too]

Posted by Jon - Laser Engines on 30/07/2020 12:08:25:

More cylinders means more fun

Very nice Jon 👍

[GrumpyGnome]

Yes, VERY nice!

Re overpowering, it seems a personal thing... I think if an aeroplane can hover/prop hang, it has excess power - may as well fly a helicopter but that is just an entirely personal thing. I know many of my club mates feel that unless a plane is capable of unlimited vertical climbs, it is underpowered. To me this seems at odds with 'real world'..

GG

[Jon H]

Posted by GrumpyGnome on 18/01/2021 07:42:11:

Yes, VERY nice!

Re overpowering, it seems a personal thing... I think if an aeroplane can hover/prop hang, it has excess power - may as well fly a helicopter but that is just an entirely personal thing. I know many of my club mates feel that unless a plane is capable of unlimited vertical climbs, it is underpowered. To me this seems at odds with 'real world'..

GG

I agree GG

I have a model that i use as a flying test bench but its nickname is the flying park bench due to its rather beefy construction. Its about 20lbs, 86 inch span and not exactly pretty.

Anyway i use it for testing engines (duh) and its had a Saito 450 radial, ASP400 radial, OS 240/320 pegasus, OS300 gemini, Magnum 240, ASP160, Laser 240, 300, 360, 180 petrol and 120 long stroke all fitted at one time or another

Although it might be surprising, the model was very pleasant to fly on all of those listed engines. Everything from about 2.4hp to around 5hp. Rate of climb suffered a little, but the model was still aerobatic even on the smallest of engines. Was it more aerobatic on the more powerful engine? yes. Was it a case of transforming the model from boring to fun? no.

The main advantage of the bigger engine was an improvement in c/g and in all honesty i noticed that more than the power.

[Mike Sedge]

The Beast!

Edited By Mike Sedge on 18/01/2021 10:49:04

[Mike Sedge]

Really enjoy flying this girl, very well behaved and on rails.

[Mike Sedge]

Haven't finished sorting the cowl out, going for a split one with magnets and screws. Got the design sorted just need to muster the energy to finish it off.

[Mike Sedge]

The DLE 40CC is not as loud as other DLE's I've used but it certainly fits the bill, love it!!!

[Mike Sedge]

Ran the engine up on the stand and the excess end of the restraint strap punched a hole in the side hence "The Beast" was born.

Edited By Mike Sedge on 18/01/2021 10:56:40

[Rich too]

I like that Mike. The engine will look great poking out of each side if the cowl and twins sound great. If you need lead up front why not fit a big motor - it’s your choice.

[Mike Sedge]

Thanks Rich, Yep couldn't agree more, didn't need any lead whatsoever and turning the weight to power certainly worked well in this case. It's a pleasure to fly and looking forward to getting cowl fitted, will post some pic's Once it's done.

Edited By Mike Sedge on 19/01/2021 06:48:50

Edited By Mike Sedge on 19/01/2021 07:01:48

Edited By Mike Sedge on 19/01/2021 07:02:58

[Robin Hood]

Just found your post. I'm in the final stages of assembling an acrowot xl with the same dle40.

Did you post the pictures of the cowl fitted or do you have any that you could upload?

[Martin Harris - Moderator]

Welcome to the forum Robin. I’m afraid Mike hasn’t been on here lately so he’s unlikely to pick up your request.