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Member postings for Jon - Laser Engines

Here is a list of all the postings Jon - Laser Engines has made in our forums. Click on a thread name to jump to the thread.

Thread: Seagull Hurricane Laser
20/04/2019 22:22:39

didnt get a chance to get on the phone today, been a busy one.

From your description i think your large rudder input may have been the trouble as trimming makes no difference to end point and only moves the centre position. Using large rudder deflection through turns with a warbird is unusual and not something i have ever needed to do. A small amount to tidy up the turns is always a good idea but 'significant' deflection may have caused a pitch down moment. My smaller Hurricane will dive sharply if the rudder is moved beyond a certain defection. My cap 232 used to do the same and was a nightmare to knife edge.

Even so, if the elevator travel was any where near where it was after we finished the setup flights it should have been more than man enough to overcome this as the elevators are very powerful. I didnt use the rudder hard over at any point during my time with it so cant say for sure, but it seems unlikely as the rudder authority was lower than the other controls when i flew it.

19/04/2019 21:11:33

thats a pretty sad looking Hurricane. Ill give you a call tomorrow but in the meanwhile i agree with the other guys, dont bin it. From here the damage looks very repairable

Thread: Thunder Tiger Manual
18/04/2019 17:44:08

By all means Cuban.

Engine tuning is a topic that is pretty difficult to write down. As with flying, driving, sailing etc so much of it is down to feel and being able to understand what you are being told by your piece of equipment.

Apparently full size Gloster Gladiator pilots can tell if they are out of trim in yaw as the rigging wires on the wings 'sing' to them. P51 pilots can similarly tell they are approaching a stall due to the whistle of the air over the gun ports.

To me an engine out of tune sticks out like a sore thumb, and by out of tune i mean perhaps a few clicks of the needle at absolute most. Its a bit like when you spot a dead pixel on your tv. until you noticed it you had no idea anything was wrong. Now you know what to look for, you cant look at the tv without spotting it. Im sure any musicians in the house will be able to spot out of tune instruments a mile off and Its the same with engines. once you learn the language, its really easy to spot when they are unhappy.

18/04/2019 08:47:03

14x7 is a good start point for the t6. if you feel the model is running away a bit then you might want to try 15x6 instead. i use this on my laser 80 equipped hurricane as i found overall speed control easier and it prevented the model accelerating when off throttle in a dive

17/04/2019 22:44:43

not being able to hear is the only valid reason for using a tach to tune an engine and for those so afflicted that is fair enough.

The reason its a bad idea for everyone else is that the revs you see will vary day to day due to a number of factors.

If you have a cold day with air that is nice and dense the engine will usually run slower as there is more bite on the prop. The opposite is true for hot summer days when the air is thin. This can be counter intuitive as most would expect engines to run slower on the hot days as there is less air for the engine to burn and so less power is produced. While this is very true, its the load on the prop that will determine the revs, but revs dont mean power even though both are related. In any case, if you have ever flown on a hot day and found the engine ran fine but the model staggered around like a wounded elephant this is the reason.

In any case, if you see 8500 on one day, then 8300 on the next, you may be tempted to lean the engine off a bit as you go in search of your missing 200 revs. As you do this the engine will warm up, and revs may drop to 8200. Puzzled, you then twiddle some more and no matter how lean you screw it 8150 is now the best you can get as the engine sits there, flat out, getting hotter and hotter, and slower and slower. I see it all the time, dont do it. leave the tacho in the box and only use it for the odd reality check and for comparing props.

setting a low idle is vital and a tach can be handy in this regard but only because it tells you for sure what the revs are. The actual idle rpm will vary engine to engine but i would aim for 2000rpm on most 4 strokes around 90 size. Poor low end tuning and/or high nitro/oil fuel will hamper a nice idle. A good plug is also important.

When it comes to props my old os 91 used to go like the clappers on an apc 13x9 when fitted to my arc carosel. I would have used a larger prop but it would have hit the ground. I later used the engine in a cap 232 (14x7 apc) and a p40 warhawk (15x6). Dont be tempted to under prop 4 strokes and always favour diameter over pitch where possible.

Clearly final prop choice will come down to the model you intend to power with the engine. What was it you had in mind?

17/04/2019 17:03:07

Dont tune with a tach. It will lead you down a path of chasing rpm and you dont want that. Just tune the engine by ear and make sure it holds power for 10-15 seconds. If so its off to the races.

17/04/2019 15:36:17

Treat it like an OS 91..or more or less any other 90 4 stroke. 5% nitro fuel with 15% synth oil. 14x7-8, 15x6-8 and perhaps 16x6 props, OS F glow plug and .1mm on the valve clearances.

A friend had one and ran it on laser 5 fuel with a 15x6 jxf prop. Went really well.

Thread: Zenoah 38 conundrum
16/04/2019 12:41:40

While it might take a little gymnastics and 5 arms you could try running the engine off of a squirt bottle just to see if it runs normally when directly fed with fuel. If you can keep it running and get it up to full power, even for just a few seconds, it would at least give you a clue as the engine wont make it to full power if there is a problem with under piston compression etc.

Thread: Hi I'm Laura
13/04/2019 09:51:14
Posted by Laura Stevenage on 13/04/2019 09:26:36:

Oh and why is this a "madhouse" lol!? Laura x

Give it a few weeks and you will have your answer

I echo the comments of the other guys though and welcome you back.

I suppose the next step for you would be to work out exactly what equipment (if any) you current have from your father, and then consider which direction you would like to go. I personally favour an ic (internal combustion) engine powered model but others favour electric. There are pro's and con's to each so you have decide on what you think is best.

Thread: Acrowot with laser 80
11/04/2019 10:27:13

The character of an engine is everything. Some are fussy, some are laid back, some are vicious, and some even seem bright and happy to see you start them up. Its quite remarkable really and can make quite a difference to the enjoyment of a model.

Tiger moths etc call for a laid back sort of engine that really couldnt give a rats about anything you throw at it, where as the acrowot demands an engine that likes to get up and go. Swap them around and the two models just would not feel right. It should be noted though that many engines have dual personalities as a prop change on our 180 can make it laid back (20x6 etc) or pretty lively (17x10 or 18x8).

Running our range on the test bench is always a fun time and the 240v is one of my favourites as i slap a 16x8 on it and wind it up to near 10k. Having a 40cc twin screaming away at those sorts of revs always brings a smile to my face

I dont recommend flying it at those revs though, might be a little loud

11/04/2019 08:25:11

Our 70 is/can be a screamer if you so choose. Its good to 14000rpm if you really want. I personally wouldnt use it over 10000 or below 9000 in general use. 13x6 gives you around 10k, 13x7 around 9k. 12x7 sits up near 10 again. 14x6 is likely to be a little to much if you want maximum performance.

Thread: Hawker Typhoon
09/04/2019 16:27:13

Martin, if you get a moment watch some of Kermit week's videos on youtube. The basic problem he seems to have is he has more or less one of everything with wings ever made. In almost every video you hear about another project he has stashed away somewhere.

The sabre engine for many years was also the big issue so if he, these guys, and the group in canada doing a typhoon can all get together its likely there will be some progress. I think the canadian group are intending to re-manufacture from scratch using original drawings. Frankly, i think this is what they should be doing with all of these older engines as safety and reliability can only be improved by using new parts.

In any case, their target for flight is 2024 i think so fingers crossed it wont be long

Thread: matt fuelproofer
09/04/2019 15:10:56
Posted by David P Williams on 09/04/2019 14:52:02:

Dougie - see my earlier post - Aerokote works fine, it's from Deluxe Materials and available direct from them, or most model shops and online stores sell it. £10.25 plus £5.75 for the matting agent.

Do you thin it with cellulose? I am always on the lookout for a decent fuel proofer that i can spray over enamel. I have become quite good at dusting cellulose based stuff over enamel without it eating the paint but if i can avoid that precarious situation it would be great!

Thread: Laser tank breather
05/04/2019 08:17:03

no problem Glenn

Its a question i often get asked, i suspect due to people being used to pressurised systems. I have also noticed that sometimes there is tendency to over think it and make it too complex. When it doubt, just keep it simple

Also, Berts example will work fine but as the breather is also the tank overflow when filling you do risk spraying fuel all over the inside of the cowl when the tank is full. Thats why i recommend having the pipe outside the cowl. Just make sure you know where its pointing or you may end up with fuel soaked trousers....ask me how i know

04/04/2019 20:29:37

The two easiest options are:

Glue a small wooden block into the front of the cowling then drill through it with a 3mm drill. Stuff a small section of brass tube up the middle, more glue, job done. It should poke out a few mm and point directly forward.

The alternative is to take one of those bent brass tubes from a dead fuel tank and clamp it to the firewall with an undercarriage saddle clamp. This can then drop down just below the cowling and again be pointed into the airflow.

This photo (sorry its sideways) shows option one employed on my acrowot xl

breather 1.jpg

and this shows option two on my hurricane. where the silver cowl joins the white you can just see it.


Hope this helps

Edited By Jon - Laser Engines on 04/04/2019 20:30:08

Thread: Laser Engines - Technical questions
03/04/2019 18:48:31

No worries Don. I use a small drop of cyano on mine as it isnt great at sticking to glass/nylon or aluminium. its also super convenient as a have a tube of the pound land stuff on hot standby at all times!

Thread: Engine for largish cw Cub
02/04/2019 16:54:14

Yea, swing a 15x6 and the 80 will be fine

Thread: Pre-Ignition?
02/04/2019 16:18:56

are you running the glow off of a power panel? if so you might have the dial turned up a little too high. That or the prop/spinner is not really biting into the prop driver nicely. In this case, fold some 400 grit sandpaper and glue it together so you end up with a flat piece that is gritty on both sides. Drill a hole through it and you can then use this between the prop/driver or spinner or whatever part you think might be slipping.

Thread: saito 82b consumption
02/04/2019 08:20:57
Posted by Brian Dorricott 1 on 02/04/2019 00:00:42:

Think I might go up an inch or so reduce the revs but keep the pitch and with a 14x6 I can trim the runway grass as well ! Ken Tulloch is the Wots Wot overpowered with the 82 ? Just wondered because the Acrowot looks on a paper a little overpowered I think a 62 would have been ample .

We do have one chap using one of our 80's in the acrowot and he had no trouble with grass trimming on a 14x6 so dont be worried about it

Thread: Laser Engines - Technical questions
01/04/2019 22:15:18
Posted by tigerman on 01/04/2019 17:26:48:

I am sure I am right but best make sure before I buy .I have a Laser 80 and want to buy the Seagull Junker CL1 ( the first World War monoplane ) If Jon is out there could you just put my mind at rest .I am sure the Laser 80 will fly this model OK .I think ?

Edited By tigerman on 01/04/2019 17:27:55

Yup, the 80 will walk it. use a 15x6 prop and all will be well.

I just looked at the specs again and the 80 will give the model more or less unlimited sport aerobatic performance. Looks like a great model though and from the instructions it looks dead easy to mod for the lower tank position should you mount the engine inverted. 

Edited By Jon - Laser Engines on 01/04/2019 22:18:29

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