Laser 160 inline twin

[Ron Gray]

8 hours ago, mike skingle said:

are ypu going to get to fly the mustang this week?

'fraid not Mike, I ran out of time as we had the grandkids staying with us over the weekend then I was working Monday and Tuesday and flying Wednesday and today. Back in the workshop tomorrow so am now aiming for next Tuesday.

[Ron Gray]

Things are on track for a maiden flight tomorrow, so I thought I'd better check out the engine to make sure it would run! 2 videos follow, the first run was curtailed after a couple of minutes as the spinner worked loose which I traced back to a slightly loose prop. The second run was a lot better (was a bit rich but I've leaned it a bit since the run) as I had also built in a throttle curve on the Tx and with that in place was able to have more control over the throttle. At WOT is was running at 8.9K rpm, spinning a 16x8 APC prop. Love the sound of it and can't wait for the flight.

 

 

 

[john stones 1 - Moderator]

A question Ron, or anyone, does a twin of the same size as a single turn less prop ?

[Jon H]

15 hours ago, john stones 1 - Moderator said:

A question Ron, or anyone, does a twin of the same size as a single turn less prop ?

 

Its a very complicated question but multi cylinder engines have higher internal friction with all the added components inside. This can cause loss of performance vs a single of the same capacity but the multi has the advantage of more regular power pulses. Our inline twin is a great example of this as power pulses 360 degrees apart mean it tolerates larger props better than our mostly equivalent cc single and a bit better than the V or flat twin designs.

 

This whole picture is further complicated by differing bore/stroke ratio's between the engines and a variety of other factors but at our scale it makes no real difference. 

 

In the case of the 160 inline its closest single cylinder match is our 155 and the 160 (FT, V and I) is more powerful on all props.

I also have an OS FT300 twin and FF320 flat 4. Both offer almost identical performance with the twin slightly ahead despite a displacement deficit. I suspect however that this is down to the carb more than anything else as the 320 has a smaller carb and longer induction pipework. A small carb will have been used to make the engine easier and more tolerant to tune as one carb for 4 cylinders is not ideal if each cylinder is at its limit of performance. 

[john stones 1 - Moderator]

Thanks Jon.

[Ron Gray]

Ready to take to the skies (yes I know that the pilot is missing, as are the doors, I ran out of time!!!!)

 

 

[mike skingle]

Ron looks goods and sounded good on the video. Looking forward to seeing the flight video. 

Wheres your cooling air exit?

[Ron Gray]

User the rad belly bulge, like yours, but I'm using the fuse as the duct! No overheating problems today but it was 'kin cold. Vids to follow .............

[mike skingle]

When the engines running it'll make a great hand warmer on a day like today

[Ron Gray]

Here is the video, not up to the usual standard I'm afraid but it gives the general impression of the 'stang and its wondrous power unit. Motor was running slightly rich still but plenty of power to hand. Mistakes on take off as a result of too much rudder input and no subtle elevator control to keep the tail down.

 

 

[Chris Walby]

Sounded great, but IMHO no chance of ever getting that through an 82dB noise test ?

[Ron Gray]

It is slightly underpropped (16x8) for the first few flights and I would expect the noise to drop quite a bit with a slightly larger prop, that's been my experience with my other Lasers which tend to rev at just over 8000 rpm (the 160i is hitting 9000). We're fortunate that we don't have a noise restriction at our field but tbh the tone of the engine is such that it doesn't offend people, unlike petrol 2 strokes!

[Ron Gray]

Whilst there has been a lull in flying gI thought I'd pull my finger out and get the zorst stacks sorted:

 

 

The stubs are hollow so should help with the cooling.

Edited April 25, 2022 by Ron Gray

[mike skingle]

Very nice Ron

The extra cooling may help in the summer months.?

[Ron Gray]

Thanks Mike, it’s not shown any signs of overheating yet but then it hasn’t been above 18 degrees!

I’ve been flying mine on a 17x8 prop which is great but I really miss the ‘edge’ on the noise that the 16x8 gives so may go back to it.

[Ron Gray]

On 29/03/2022 at 20:30, Chris Walby said:

Sounded great, but IMHO no chance of ever getting that through an 82dB noise test ?

I did some noise tests up at the field yesterday using a ‘proper’ calibrated sound meter plus an app on my iPhone equipped with an external mic with dead cat. (As an aside, the iPhone was a very close match to the sound meter). The model was sitting on the grass runway (not held up as per the ‘official’ test) and I took readings from all around the model at 7m distance. Using an APC 16x8 prop the lowest reading was 80Db and the highest was 89Db, using a 17x8 prop the lowest was 78Db and the highest was 85Db.

 

I also did back to back flights with the 2 different props and my findings were that in terms of outright performance in level flight there wasn’t a great deal of difference, vertical performance was slightly better with the 17x8. Noise, the 16x8 has a slight ‘edge’ to the sound which I like. The 17x8 gave me 2 - 3 minutes more flying time (I know this is a difficult one to judge as it’s almost impossible to exactly mimic each flight). Conclusion, I will be using the 17x8 prop in preference to the 16x8.

[Chris Walby]

4 hours ago, Ron Gray said:

I did some noise tests up at the field yesterday using a ‘proper’ calibrated sound meter plus an app on my iPhone equipped with an external mic with dead cat. (As an aside, the iPhone was a very close match to the sound meter). The model was sitting on the grass runway (not held up as per the ‘official’ test) and I took readings from all around the model at 7m distance. Using an APC 16x8 prop the lowest reading was 80Db and the highest was 89Db, using a 17x8 prop the lowest was 78Db and the highest was 85Db.

 

I also did back to back flights with the 2 different props and my findings were that in terms of outright performance in level flight there wasn’t a great deal of difference, vertical performance was slightly better with the 17x8. Noise, the 16x8 has a slight ‘edge’ to the sound which I like. The 17x8 gave me 2 - 3 minutes more flying time (I know this is a difficult one to judge as it’s almost impossible to exactly mimic each flight). Conclusion, I will be using the 17x8 prop in preference to the 16x8.

Hi Ron,

 

Really sorry to say, but the test needs to be as per the requirements or its not representative of a full and correct test. I have experienced club testers that did not follow the guidance and thus failed the model. Another approved tester took over and carried out the test correctly and the model passed.

 

The last two models were a Laser FT200 and a Super Tigre G30 powered and were very challenging with initial dB levels in excess of 88dB. By far the worst noise levels is from facing the prop (86dB compared with 78 dB from the other three sides) and with any sort of breeze I get a "zingning" and the reading is all over the place.

 

The G30 it just scrapped through with the prop canted just off vertical to stop additional wind noise or either stand there until the light breeze subsided. The reality is that both models fly at 1/2 throttle, but that's not the point.

 

The rules are the rules unless they get changed (very unlikely) so either comply or fly where there are less noise restrictions. Just don't get me on the subject of over propping - no winners in that game IMO

[Ron Gray]

@Chris Walby with respect you do not know what I did for these tests, I have only made a comment that I didn’t have the model held up in the air. But with that exception I followed the DoE Code of Practice for model aircraft! Bear in mind this is not an ‘official’ on behalf of Laser post, it is more in response to your comment made on the 29th March.

 

It really is indicative of forums where one tries to help but some people try to shoot you down, good job I’m thick skinned and just love dealing with those situations / people. 

[Jon H]

As has been discussed many times the noise test method used for testing model aircraft is flawed in so many ways we might as well not bother with it. 

 

The zinging problem chris points out is the typical mode of failure for most models with air flowing back through the prop due to wind or whatever else. Given the other readings were so low it should just be ignored in my view, or the meter set to damp out those peaks. Most clubs i have seen take the peak reading and this is fundamentally wrong even according to the bmfa guidance. 

 

I asked Ron for figures as another potential customer was asking and i have no data beyond a steel test stand stood on and surrounded by concrete. I just wanted a ballpark figure to back up my perception that the engines were not especially loud. Given the models were tested in a less than ideal condition means that a test conducted with the model off the ground would offer an even more favourable result. 

 

We all want to keep our sites and models absolutely should be silenced to a sensible level. but the sort of inflexible and badly applied noise testing most clubs offer is not helping anyone. 

 

Its irrelevant anyway as no amount of noise testing will protect a club from a complaint and we can all tell when a model is loud in the air.  

[Ron Gray]

Oh what fun was had today, the 160 in-line is getting even better, here’s a short burst vid of it on fly by.

 

[Ron Gray]

Nice evocative shot

 

[Ron Gray]

Very short vid of worm's eye view of flypast 

 

 

[Ron Gray]

After another re-tune it was time to try out d=some formation flying with a leccy powered H9 'Jug' - what fun.

 

 

[Martin Harris - Moderator]

Hard work, isn't it!  Nice take off and landings too...?

[Kevin Fairgrieve]

And the two protagonists

 

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