Acro Wot XL Engine Choice

[Former Member]

[This posting has been removed]

[Frank Skilbeck]

Interested too, I have an ASP 108 2 stroke glow looking for a home and wondered if that would be man enough.

[Jon H]

I think a 120 4 stroke would probably be the smallest for what i would call good performance. It will fly on less i am sure, but it wouldnt have much oomph. I am sure the 108 two stroke would be plenty

[Bob Cotsford]

I'd guess that a 108 2 stroke would be roughly equivalent to a very good 120 4 stroke glow or a 20-25cc petrol 2 stroke? No doubt it would get the AW XL off the ground but I doubt the experience would really be worth the hassle of starting the engine in the first place. I'd say that a 120 2 stroke would be the absolute minimum needed depending on how you like to fly. If you are a bit of a hooli then you might want more power.

Mine has a 38cc 4 stroke petrol and if noise wasn't an issue I would swap it for a 35cc 2 stroke petrol. As it is it flies very nicely with no real shortage of power, e.g. it will pull a reasonable height stall turn and largish loops, but the 4 stroke is a bit weighty for the airframe.

[Bob Cotsford]

Different strokes Jon!

Jon probably knows best but if it were me, I'd be tempted to stick a 180 4 stroke glow in.

Edited By Bob Cotsford on 26/04/2017 10:32:34

[Allan Bennett]

What is an Acro Wot XL? I don't see it on the Chris Foss web site, but I do see the Xtra Wot, which is what I have. Is it the same thing?

My Xtra Wot used to fly on an OS120FS, which was then replaced by an OS120AX to reduce the noise. Both were good for my relaxed flying style, and could take it vertical. The model is currently powered by a 2000-watt electric setup.

[Frank Skilbeck]

Allan here you go

[Bob Cotsford]

The Acrowot XL is the ARTF translation on the kit build XtraWot. As is the way with things, it's grown a little from the Xtra.

[Allan Bennett]

Ah, so it's under the Ripmax banner rather than Chris Foss, and 79" wingspan vs. 71" for my XtraWot. Thanks guys.

[Stuart Marsden]

This is all very interesting and shows, horses for courses. I would say to the guy putting in the Irvine 72, just to double check the C of G, as not enough power with a rearward C of Gcould be tragic, slight nose heavy is always. Best to start with. I have another issue which you all may help who already have this model flying. The previous owner and someone else I know says the elevator push rod vibrates like bell and wonder if anyone converted to move the servo to near the stabilizer and how they configured this?

[ChrisB]

A chap in our club has a DLE 30..ish in the front and its just ok. I wouldn't go for anything less than 30cc.

[Bob Cotsford]

Posted by ChrisB on 26/04/2017 21:38:11:

A chap in our club has a DLE 30..ish in the front and its just ok. I wouldn't go for anything less than 30cc.

[Former Member]

[This posting has been removed]

[Tim Flyer]

Interesting thread. I use a Laser 155 on a Wots Wot XL (turning a17x8 at approx 7500rpm)which is perfectly fine power wise. It flies beautifully but vertical is not unlimited. The Wots Wot XL is much more " draggy" than the Acro Wot XL and heavier being a biplane. I think the Laser 155 would be superb in the Acrowot XL with great vertical. I have been tempted to do a switch myself and put a Laser 200v in the Wots Wot XL for unlimited vertical and put my 155 into an Acro Wot XL. ....but that's a few projects away!

[Neil (Itisme)]

I have a DLE30 in mine with the servos for the elevators mounted in the tail, batteries placed under the servo tray for the rudder servo got it to balance without any extra lead, i find the 30 more than enough for loops as big as you want it will take off in a couple of meters without trying.

[Richard Wills 2]

I have an ASP 180 fs in mine, 18x6 prop. It is perfectly powered, as much vertical as you need and sensible speed, although I wouldn't use the asp again. Throttling leaves a lot to be desired.

My brother has a Wots Wot XL with an asp 160 twin.  It flies it, but feels underpowered and is not much fun.

Edited By Richard Wills 2 on 27/04/2017 12:34:19

[dave parnham]

So is it better? than my aging XtraWot kit that I brought from Mr Foss's Car boot at Sandown all those years ago?

I have a Laser 150 in mine.....is it time to go ARTF.

She could do with more power for the vertical, but its a great plane to throw around, not 3d but good enough to enjoy yourself, sadly it needs a complete recovering job.

dave

[Bob Cotsford]

Posted by Timothy Harris 1 on 27/04/2017 10:54:13:

Interesting thread. I use a Laser 155 on a Wots Wot XL (turning a17x8 at approx 7500rpm)which is perfectly fine power wise. It flies beautifully but vertical is not unlimited. The Wots Wot XL is much more " draggy" than the Acro Wot XL and heavier being a biplane. I think the Laser 155 would be superb in the Acrowot XL with great vertical. I have been tempted to do a switch myself and put a Laser 200v in the Wots Wot XL for unlimited vertical and put my 155 into an Acro Wot XL. ....but that's a few projects away!

Interestingly I have the same engine setup in both an Acrowot XL and a Wots-wot XL. I don't think that there's a huge difference between the two. The WW has the drag of two wings, but the AW has a greater span and length. Both have a suggested engine size of 25-35cc. The AW is bigger all round and I think that they both weigh about the same. The WW may fly a little more slowly but both have a similar vertical performance.

[Tim Flyer]

Thanks Bob. Sounds like I should stay put then and keep the 155 in the Wots Wot. I'm perfectly happy with it as it throttles very very well and is a relaxed flyer for big loops etc. Maybe if I do buy an Acro Wot XL I would try the 200v in that instead.. should be fast too. Anyway I need to build my p47 first.. Happy Flying all😊

[Rich too]

Yes, my WWXL has an OS33GT and I would not use anything with less power.

[Alve Hansson]

I have an OS GF30, with 17X8, in mine and it can roll straight up until I can no longer see it anymore,

that engine is enough for me .

[Paul Marsh]

i have a Saito 182 flat twin in it.

[Jon H]

More cylinders means more fun

[Richard Clark 2]

I think many people greatly overdo the power.

My 15 years old Astro Hog is 72 inch span, covered entirely with doped, colour sprayed, and fuel proofed nylon, broke in half once due to my not paying attention  and had to be repaired so weighs eleven pounds

Its OS 91 AX two stroke on a 16 by 6 prop provides endless and fast verticals,  going vertically OOS so easily you really  have to watch it,  even from take off when the speed starts off low. So much so that the quick vertical acceleration is easy to see.

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

[Paul Marsh]

The Saito 182 TD is just over 1kg in weight, the OS 120 AX is 647g, without muffler, which weighs around 300g. so its the same.

even a few grams on this size won't make a difference, in fact weight on the front end is needed anyway, instead of adding weights.