If you ask ten different aeromodellers...

[David Davis]

...you'll get eleven different answers so I'm expecting quite a diversity of answers to my problem.

I've had an ARTF Acrowot for too long now so it's about time I got on with assembling it.

Engine. I have at least three engines which could power it: a Laser 70, an Irvine 52 and an OS 61 SF. In fact I own two OS 61 SFs and I've used this engine in the past in my much lamented kit-built Acrowot. I found this to be a very pleasant combination. I've never run either the Laser or the Irvine.

Question 1. Of the three engines mentioned above, which would you use in an ARTF Acrowot?

Servos. I have the option of fitting Hitec HS 5485HB or standard Hitec 311 servos to this model.

Question 2. I was thinking of fitting the 311s and reserving the 5485s for a Dave Smith Aerostar I'm planning to overhaul. What do you think?

[Keith Berriman]

So if I am the first to reply

I think the Hitec 311 servos should be okay for this lighter model

On the engine side maybe the Irvine but don't go mad with throttle I think the laser maybe to heavy and 61 too powerfull for this lighter model

Enjoy the build and flying I miss mine as the were in short supply when I needed a replacement

[Andy Stephenson]

Dave,

1 Laser 70 for the Acrowot, the OS 61SF needs to be reserved for the patternship.

2 311s are more than adequate for the Acrowot.

A.

[David Davis]

Andy, I have two OS 61SFs so I could put one in each model.

[Chris Walby]

David,

I have one with a Laser 70 in it and its great, no added lead in the tail and it comes out spot on the target AUW. Flies nice, sounds great and no issues landing.

Servos I can't help with that has not already been said above, but good standard ones should do the trick.

Any question please ask.

[Martin Harris - Moderator]

Another vote for putting the Laser in the Acrowot with any decent quality standard servos perfectly adequate.

[John Stainforth]

Why not keep the engine choice flexible?. With careful choice of bearer spacing it is possible to accommodate several different engines in the same plane. For example, the Saito 72 and 82 have crankcase widths of 35 mm and crankcase mount hole spacings of 46 mm; for the OS 46AX these dimensions are 35 mm and 44 mm; the OS55AX 36 mm and 44 mm; and for the Laser 70, 35 mm and 45 mm. All of these engines can be mounted on Hangar 9 metal engine bearers if their inner faces are spaced about 36 mm apart. These mounts have slots that allow for the variations in the fore and aft spacings of the mounting holes and for different fore and aft positions of the engine.

[Richard Wills 2]

Laser or Irvine, OS 61 would be a tad heavy and the exra power is not necessary. Any standard servo will be more than good enough. Mine has an OS 50 SX and Futaba 3001's all round, balanced perfect. You will need a silencer manifold extension block for the exhaust on the 2 stroke

[Dave S.]

I've built and flown at least a dozen Acrowots (from the kit) and the best engine all round was the OS 70 Surpass, in my opinion.

I have an ARTF Acrowot upstairs and have just bought a Saito 82 to try out in it. I'l let you know how it goes.

[Bruce Collinson]

Ditto what Chris W writes, adequate power, no ballast and can run on very low oil. Subject of course to what Jon says when he gets here.

Either way, you're spoilt for choice.

BTC

[Nigel R]

311 all round with the Laser up front.

Much as I like the SF engines, very smooth running, brilliant carbs & build quality, etc, fact is the Laser weighs less than a 61 SF... it might sound wrong but

SF with silencer, 680g (!)

Laser 70, 580g

For completeness, I believe the Irvine 52 is approx 520g

[Nigel R]

turns out you'll get the same 10 answers, might not be what you expected!

[brokenenglish]

David, I've been flying an Irvine 53 in an ARTF Acrowot and it's perfect. You need very minor surgery to accommodate the silencer, but you have more than enough power.

I'm just using cheap HK servos (also in a lot of other planes) and I've never had a problem.

[john stones 1 - Moderator]

Four stroke for me, plenty pull, sounds nice.

[Tim Flyer]

I would go for the Laser 70 personally although both the other engines are fine . Reason being the better sound and easy handling and fairly economical fuel cost and ability to run on low oil fuel. Like a few others my ARTF Acrowot has a Laser 70 powering it and it’s a very nice match .

[Peter Christy]

Ye Gods! You guys like over-powering things! Mine is ballistic on an Irvine 46 and that with the "quiet" silencer! And yes, the CofG was spot on!

--

Pete

 

Edited By Peter Christy on 21/01/2021 17:36:43

[Tim Flyer]

My C of g is spot on too with a LIFE battery and no added lead😊. As it’s an aerobatic model plenty of power is good .!

[Tim Flyer]

In terms of power a strong 45 2stroke isn’t much different to a 70 four stroke although the 4stroke would probably win on static thrust but a 4stroke weighs more.

Edited By Tim Flyer on 21/01/2021 18:22:13

Edited By Tim Flyer on 21/01/2021 18:23:15

[Nigel R]

Aye, the irvine 52 is a bored out 45 and almost identical in power i would guess, to the last 70.

45 would be proportionally less power.

One thing about putting a big engine in is that you can prop it for lower revs - less revs is the easiest way to make it quieter.

[Paul Marsh]

Mine has:

Engine: Thunder Tiger 75 four stroke

Servos:Hitec HS5485 Digital servos @£17. each

Though any 70 FS will do.

[Rich too]

Laser 70 👍

[Chris Walby]

David,

Turn the question around a bit....What type of flying do you intend to do?

My Laser Acrowot excels at big and small aerobatics and makes me look good with predictable flight characteristics.

If you would prefer something more "manic" with prop hanging capability or the noise of a 2 stroke then perhaps a different engine choice is more appropriate. Nothing wrong with 2 strokes (have two 46's in my Extra Slim Twin and that's for that manic feeling!).

So the question is....what do you fancy sir?

[David Davis]

Having slept on it I have decided to fit the Laser and the Hitec 311s to the Acrowot, the OS and digital servos to the DSM Aerostar and I'll reserve the Irvine for a WOT 4. I've had the kit sculling about for years but then I expect that we're all hoarders aren't we!

I've always liked four-strokes ever since I bought my first, an OS 40 Surpass and it seems I've gained some fame/notoriety for campaigning a fourstroke in that daft competition I participate in every year, La Coupe Des Barons. I admitted elsewhere that the wing on one of my Barons came off in practice entirely due to my own negligence, the fuselage was wrecked but it provoked the following encouraging response from a fellow competitor. I'll be running a Thunder Tiger 54 this year.

Jacques Girodet

Courage

David John Davis

, l'anglais 4t de la coupe des barons, pour le 12 juin tu as largement le temps .... car TOMIO t'attend

 

 

Edited By David Davis on 22/01/2021 07:32:48

[Bob Cotsford]

Posted by Chris Walby on 22/01/2021 06:49:58:

David,

Turn the question around a bit....What type of flying do you intend to do?

My Laser Acrowot excels at big and small aerobatics and makes me look good with predictable flight characteristics.

If you would prefer something more "manic" with prop hanging capability or the noise of a 2 stroke then perhaps a different engine choice is more appropriate. Nothing wrong with 2 strokes (have two 46's in my Extra Slim Twin and that's for that manic feeling!).

So the question is....what do you fancy sir?

On this tack, my nephew had an ARTF Acrowot fitted with an ASP46 which he could throw around in a quite spectacular manner entirely within our small fields boundaries. My own experiences with the kit AW are similar, with a 40 2Str or 52 4Str it would turn on a sixpence and could go through the book without leaving the strip, on the other hand fitting a 61 2Str or a 70 4Str turned it into a big sky monster with outsize loops and unlimited vertical rolls. It really is a one size fits all design.