ESM Tigercat - powered by Laser engines

[Ron Gray]

I did start posting bits about this model on the Laser Models thread but that is really supposed to be a gallery and I have been asked to add more details of the model so here we go. This is not a build blog!

I acquired the model about a year ago and it had been built and successfully flown as a leccy jobbie. However I/C was the way I wanted to go and the idea was to get another Laser 160v to add to the one already in my collection. Unfortunately that was not as easy as it sounds as those of you who follow Laser's developments will know. I had given up hope of getting one and had started to kit the model out for electric power and had constructed and fitted 2 battery boxes into the nacelles. Unfortunately when I came to do some ground testing, the performance was somewhat underwhelming so I was just about to upgrade the motors to 10s when, out of the blue, another (BNIB) 160v materialised. My prayers had been answered so I set about cutting out the battery boxes and turning them into tank platforms, I had decided to mount the 160s vertically as this would help with the carb / tank alignment. The alterations alone took over 2 days to complete as it's not easy working within the confines of the engine nacelles.

2 SLEC tanks per engine was the chosen route as each carb needs its own supply of fuel and 2 tanks were easier to fit than 1 large one with 2 clunks. I plumbed them so that the fill lines were joined and the vent from one of the tanks went into the other tank so that, on filling, the overflow would go into the other tank. However, for some reason that caused some filling and possibly some running issues so I re-plumbed them slightly differently but the result was that each tank had its own vent. Filling the tanks is now a lot easier and to ensure that each gets full I block off the first vent to spill and then stop when the second spills.

This is a mockup of the plumbing on a spare pair of tanks

Engines fitted to etc centre section

I'll take some shots of various bits of the 'plane which may be of interest!

[Ron Gray]

The first run of the engines wan't too bad, I had managed to mechanically balance the throttles fairly close but they were out of balance at high revs and each motor needed a bit of jet adjusting to get them to perform. This video is taken from today's running and both engines, at WOT, are spinning at 7.9K. Both also tickover at about 2K (in the vid one stops before the other which I put down to it being somewhat tighter than the other one) but the midrange needs balancing. I'm going to create a throttle curve for each channel so that I can tweak that to get them closer.

[Jon H]

Left engine right cylinder is rich on the slow run, that could be why the mid range is a little out of whack. I would give that engine a retune on both slow runners and see how that improves things.

Im still super jealous. i was looking on bigplanes and they have them in stock but i cant justify it That thing is going to be awesome in the air.

[Ron Gray]

Yeah, you can see the smoke! Problem with slow run adjusting is that you can't get to them easily with the engine running, I may have to twist both carbs round a bit so that I can get to them or take the engines off and run them in the test bench.

[Jon H]

It can be a challenge when they are upright. You could try slipping some sort of rubber tube or a snake outer over the needles so they poke out the bottom. once adjusted the tube or whatever you used as an extension can be removed.

[Ron Gray]

Good idea, I'll have a look through the bits box tonight. If I can source some bits I could take it up to the field with me tomorrow, I think that the neighbours are getting a bit fed up with the noise in the garden!

[Chris Freeman 3]

Very nice project. Will be a stunner in the air.

[cymaz]

You've got to love the sound of multi engine planes

[Chris Walby]

Great project and will sound fabulous, still not sure about throttle curves as once both engines and both pots are tuned in I don't think they would vary that much at mid throttle. Will it really cause that much yaw?

If ultra concerned how about tachometers on each prop and telemetry at least you would know that one is not pulling as well as the other.

Jon, Yes Bigplanes have them, but its a significant investment on the chance that a pair of 160's will ever get made available. The alternative its to wait until 160's are on the shelf and hope the kit is still available.

All the best Ron and please keep us updated with video clips

[Ron Gray]

Well I found some suitable material for the needle extenders, paint brush handles, the hollow metal ones, they fit really well. Now I was going to take it up to the field to carry out some more engine tuning but I realise that with it in the car I can’t get anything else in so wouldn’t be able to fly, so I’ll leave the tuning for another day. I should explain that I recently changed cars, well actually we had a complete vehicle rethink and got rid of the motorbike, the VW Campervan and the wife’s car and now just have one ‘family’ car. And whilst the new car is an estate (Toyota Corolla Sports Touring) the available carrying space is somewhat less than the ‘van. In fact my larger ‘planes won’t fit in the car and are carried on the trailer!

@Chrus - I have thought about telemetry and FrSky do make a nice Gas suite system but that is for spark ignition and their rpm sensor is for leccy, so I’m still looking. The idea of the throttle curves was just to allow me to fine tune each motor so that each gave the same rom at the same throttle stick position, but it would only be used to set up the motors then left alone. Having said that, as Jon has suggested the slow running settings, once adjusted, may give me the balance anyway. The stock of ESM ‘planes that Bigplanes have is the last as ESM went bust a couple of years ago so get them whilst you can! I bought a Bearcat earlier this year and found that the ‘kit’ was missing a few bits symptomatic of end of the line! BTW the Bearcat will be using my 240v and it is also nearing completion so the 2 Laser powered ‘cats should be quite something.

More snippets to follow!

[Jon H]

Its not the investment Chris its the space. I have an airworthy fleet of 12, more than half of which are over 70 inch. I also have about 20 models in storage waiting for their turn and i have nowhere else to hang models in the house.

When i found out ESM were going i bought two models (A6m Zero and Fw190) that i knew i wanted as i knew they would never come again. I have started both, engines and retracts are fitted with small screws, cowls are cut, and in the case of the zero, the repaint has begun as it just looks too perfect out of the box and i needs to have the poop beaten out of it. In fact i should continue working on that over the winter. A bit of painting can be fun and i can do it while faffing about with the hurricane.

Ron, if you dont have far to go tie the model to the roof rack. 50 or 60mph wont hurt it and plenty of guys have done it before. Just be sure to avoid low bridges

[Ron Gray]

The trailer has a roof rack with model holder brackets, alas, I don’t have roof bars for the car. It’s just a bit of a faff to get the trailer out from its undercover storage as I have to get other stuff (grand kids outdoors play things) out of the way first and it was too cold to do that last night!

[SR 71]

I carried my last build on top of my car 3 months ago when i lived in Cyprus, had the police pull alongside and stayed there a couple of miles admiring the model, they waved good by and drove off

Tony

[David P Williams]

Yep - years ago a friend transported his Pitts that way too..

[Ron Gray]

Things are starting to move again (no pun intended)! I’ve weighed it - 12 Kg and have added about 6ozs of lead to the nose and am now happy with the C of G. Was going to retune the engines today using my paint brush needle extenders but the wife thought it a bit anti social to run it in the garden as we are ‘still in the Christmas holiday period’, bah, humbug I say! Anyway it made me get the trailer out and check the fit (fingers crossed for a maiden flight on Tuesday)

[cymaz]

Ron, run up the engines individually and check all is well, then together. If one is slightly off colour you will notice it on the individual runs.

Best of luck with the maiden. Any doubts about anything.....back to the shed/ workshop and sort it. .

[Ron Gray]

Good advice Cymaz, I certainly won’t risk it if it doesn’t feel right. Took it up the field today for some more engine tuning and I think it’s there (possibly a little bit rich on one carb on the starboard engine). Couldn’t resist some taxiing up and down the runway, sounds gorgeous when the throttles are opened, it goes quite quiet / smooth, was tempted with a flight but good sense prevailed! Fingers crossed for Tuesday.

[Jon H]

12kg is getting up there. It definitely needs engines bigger than the 90s called for on the instructions. The asm version of the tigercat was much lighter even though it had the same wingspan. I wouldn't be happy with anything smaller than a pair of hot 120s at that weight that's for sure.

Looking forward to the maiden

[Chris Walby]

Nice trailer setup there Ron.

How close are the props to the ground? Its only I noticed with George's electric (14x10) I am sure you can hear it trimming the grass (grass as tall/longer than the height the wheels) and my Dual Ace has a very springy nose wheel so if I make a poor landing it can just touch a prop.

Surprised it took 170g to get C of G, but then again my mossie has everything as far forward and some brass prop nuts..

Good luck, good preparation and as Jon says always have a plan B in mind and I am sure the maiden will be okay.

Don't forget to get someone to video it...the sound alone will be something special.

PS what's a 160 V weigh anyway?

Edited By Chris Walby on 29/12/2019 22:07:37

[Ron Gray]

@Chris - there is a 75mm clearance between the props and the ground, should be enough!! props are 17x8. I know what you mean about George's one but I think that has shorter landing gear than mine (the full-size has very long legs).

I made a mistake on the nose weight I added, its is actually 4 ozs not 6 but I'm OK with that as I was originally expecting to have to put more in, now it balances with the tailplane dead level.

Will ensure that I get a video of the maiden.

[OzFlyer]

What a fabulous model. I saw a similar one once at a fly in that was powered by two 5 cylinder radials. The sound was possibly the second best I'd ever heard (after a Rolls Royce Merlin!).

[Ron Gray]

I only took a very short video of the taxi trials yesterday (it was difficult holding the iPhone and TX at the same time, I was on my own!)

Edited By Ron Gray on 30/12/2019 13:50:13

[cymaz]

[Ron Gray]

As planned, I took the TC up to the field yesterday, weather conditions were perfect for the maiden flight, unfortunately one of the engines was playing up. It started no problem, would tickler without issues and ran up to 7800 revs at WOT. Transition from low to high was also good. However when I taxied out to the runway and ran the engines up to WOT to clear them, it cut out very time I got to WOT, it transitioned OK but just cut out. I checked the needle adjustments and despite many adjustments, including going back to 'basic' settings I just couldn't get it to run at WOT after the taxi out. Back in the pits I tried to replicate the problem (too rich?) by letting it idle for 3 - 4 minutes but then it would run up to WOT without any issues. So after nearly 2 tanks of fuel I packed it up and have decided to take the engine out and bench run it as it will be easier to get at the needles that way. The other engine ran like a dream and didn't falter one bit! Anyway, here are some shots of it up at the field. There is a video of it taxiing and as soon as I have that I'll upload it.

[Jon H]

An unusual problem Ron but a friend had something similar with his twin enya 46 powered he111. What we eventually found was that the engines were cooling off during the time it took to pick the model up, walk out with it, taxi onto the runway and by the time he was ready to go the left engine was too cold (it went lean as cold engines do) for it to run up to full power on the correct tuning for flight. Our solution to this problem was to get to the edge of the strip and hold the engines at about half throttle for 15-20 seconds before winding up to full power. Once satisfied he could then taxi out and go almost immediately before the engines cooled off and once we did this it was all just fine.

All that said, i would have expected your idle test to have mirrored your taxi experience.

In any case, dont bother taking the engine off the model as that is where it needs to work so setting it up in the bench is of no real use. My suspicion is that the engine was a fraction lean on the mains when cold so try the 15-20 second run at half throttle before giving it full power. If its still marginal at full power but solid as a rock at 80 or 90% power then just ignore it and fly. You have more than enough power so if the engine is stable at slightly less than full throttle just takeoff at reduced power and once in the air and up to height gently open it up and see what happens. Be prepared to cut it back if it shows signs of distress but i suspect the combination of going slight rich in flight and warming up will sort it out.