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Laser Engines - Technical questions

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Paul james 818/02/2019 12:30:15
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126 forum posts
23 photos

Interesting stuff Jon, good to get feedback from someone who has tried these mods. I modified an Irvine carb to fit one of my Lasers as I have the facilities to easily do so here. I found it was at least as good as the old Super Tigre style carb and a tad simpler to set up.

Bruce Collinson18/02/2019 13:09:22
364 forum posts

K Jon, ta. Never realised there were performance issues with intake manifolds. It's back to the heatgun then, now it smells of nitro!

BTC

bert baker18/02/2019 14:12:23
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1300 forum posts
278 photos

No one remember West tunes four strokes,,, the did away with the carb tube and slapped the carb straight onto the head,, just like another popular four stroke manufacturer

Jon - Laser Engines18/02/2019 15:17:42
4656 forum posts
173 photos
Posted by Paul james 8 on 18/02/2019 12:30:15:

Interesting stuff Jon, good to get feedback from someone who has tried these mods. I modified an Irvine carb to fit one of my Lasers as I have the facilities to easily do so here. I found it was at least as good as the old Super Tigre style carb and a tad simpler to set up.

The ST carbs were good but under certain circumstances they could prove problematic. The same was true of the irvine carbs and the longevity of the irvine was also a problem. Its because of this that we now make our own.

Manish Chandrayan19/02/2019 10:47:27
569 forum posts
65 photos

Does the baffling look right?

front with nose bowl.jpg

front view.jpg

left view.jpg

right view.jpg

right view without nose bowl.jpg

left view with nose bowl.jpg

Jon - Laser Engines19/02/2019 10:59:56
4656 forum posts
173 photos

Looks pretty good. There is a small gap round the rocker cover but its unlikely to be a problem. All you need now is sufficient outlet area and you should be all set.

You may want to add a support to your exhaust though as a long run of flexi pipe like that is likely to break if allowed to vibrate.

Manish Chandrayan19/02/2019 11:23:12
569 forum posts
65 photos

Thanks Jon! Appreciate the quick response.

Gap under the rocker cover you see in the second picture gets covered to a large extent when the nose bowl is attached (first picture). As for outlet can't do much, it is strictly as per De Havilland design. Will take some pictures. The cowl cheek sides and the open area on the bottom right of the cowl provide the exits.

As for exhaust tube support, yes! that is supported securely using steel strips bolted to the air frame at two places to ensure minimal movement. More pictures tomorrow

Martin Harris19/02/2019 13:32:58
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8543 forum posts
214 photos

The scale venting arrangements have always been quite adequate on my 1/6 scale Airsail Chipmunk with an OS52FS - despite some gloom and doom observations when I first presented it to the "peanut gallery"...

The position of the cylinder in relation to the scale vent is just about ideal both for cooling air and visual appearance - and the rocker tube visible on the OS only adds to the effect!

Edited By Martin Harris on 19/02/2019 13:35:43

Manish Chandrayan19/02/2019 13:58:48
569 forum posts
65 photos

Visible rocker tubes did you say Martin? See the bare unpainted spot of wood in first picture ? That's where I had them (dummy ones) only to realize that they will interfere with the Laser's fat belly and had to pull it out

Jon - Laser Engines19/02/2019 14:08:31
4656 forum posts
173 photos

The cooling on more or less all of my warbirds, my Airsail Tomahawk and to some degree my acrowot xl would probably all get the 'experts' sucking air and shaking their heads.

Over the years i have seen cowls butchered to the point that i think you could fit/remove the engine without even taking the cowl off. I assume this is due to cooling paranoia? If so its unfounded and it should be noted than the most important thing is flow. If you can get cold in and hot out then you are likely to be just fine. You dont even need that much air to get the job done but it must be able to flow freely.

Martin Harris19/02/2019 14:27:03
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8543 forum posts
214 photos

I have a 1/12 scale combat Hellcat which had a tiny slot about 3/4" x 1/4" directly in front of the cylinder of an Irvine 25. The only other hole in the front of the radial cowling was for the prop driver.

The cylinder head lay flush with a cylinder head sized hole in the bottom of the cowling - a small lip was formed at the front with the back of my covering iron to create some suction and the hole was extended to a slight egg shape at the rear. ALL* the air admitted to the cowl had to pass the fins and the literal heat of 7 minutes of mostly flat out combat never produced the slightest hint of overheating...

(A good proportion of what looks like the oil cooler openings is just painted on)

* OK - there was probably a tiny quantity around the prop driver hole.

Edited By Martin Harris on 19/02/2019 14:43:10

Manish Chandrayan19/02/2019 14:31:41
569 forum posts
65 photos

In my opinion the best examples are control line speed engine installations. Tiny slit at the front, tightly cowled engine and a fair sized opening at the rear, and those engines have to run flat out

Martin Harris19/02/2019 14:41:10
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8543 forum posts
214 photos

Oddly enough, I was inspired by reading an article on just that when I tried my minimalist cooling experiment.

Martin McIntosh19/02/2019 18:07:03
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2819 forum posts
1050 photos

In the latter stages of when I flew F3A we started to enclose tuned pipes in an attempt to minimise the noise. First try resulted in a melted silicone joiner but just a 1/4" x 1" slot at the front cured this.

My Lasers have very little cooling due to the model designs which do not allow for it, i.e. Mustang, Spitfire and to a lesser extent the Stampe.

Martin Harris19/02/2019 18:19:25
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8543 forum posts
214 photos

I think you should rephrase that as they have efficient cooling! wink

bert baker19/02/2019 18:36:37
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1300 forum posts
278 photos

Just pulling up a chair and popcorn

Martin Harris19/02/2019 18:40:06
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8543 forum posts
214 photos

Really? It was meant as a compliment on the efficiency of Martin's installation! surprise

Martin McIntosh19/02/2019 20:07:52
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2819 forum posts
1050 photos

martins ic mustang 120.jpg

Not a lot of air going in here.

tigerman01/03/2019 14:52:36
159 forum posts

One for Jon .I have a Seagull Gypsy Moth and I have a Laser 80 in the Gypsy Moth . I have always flown it on a 14/7 APC prop but I am being told I would be better flying it on a 13/4 prop .That does not sound right to me .Jon should I stick with my 14/7 or would recommend something else for the Seagull Gypsy Moth .I happy with the 14/7 but not sure if I am getting the best from the Laser 80 with that prop .What is your opinion Jon ?

Chris Walby01/03/2019 15:00:40
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926 forum posts
222 photos

Hi, Jon will offer better advice than me, but the Laser web site states 13×7-8 14×6-7 15×5-6 for an 80.

IMHO it will rev like a gooden on 13 x 4 and your original choice is spot on wink

Edited By Chris Walby on 01/03/2019 15:01:13

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