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ASM Tigercat Laser


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I have been lucky enough to acquire a couple of models from a club member who is responsible for all this twin ic malarkey with the prize being the Tigercat with a pair of Laser 100's

 

I will be doing a very thorough inspection, but the major concern is the wobbly tail section and its a ABS skin construction. 

Photo of its maiden in 2015

 

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A lot more to follow with questions and progress for this bi cat!

 

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Hi,

I have read the RCU threads from 10 years ago and it certainly seem a light/different construction with avoiding hanger rash be very difficult to achieve. The model has its issues, mostly around the gear doors and some ply parts coming adrift, but seem to fly well.

 

The investigations continue with a couple issues and questions coming up already which I could do with some assistance please.

  • Engine's - what to do asked on the Laser Technical thread
  • Glue - initial suggestions are Gorilla or No more nails although "Sticks like sh*t" (yes its a trade name!  Mods) Any other suggestions for ABS?
  • Air up/down retracts - what's the allowable air leak rate, say 100 psi and a drop of no more that xx psi in yy minutes?

More about the wobbly tail, but in short I have found the problem...its not attached, now the questing is how to re-fix it?

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        A fan of "sticks like sh*t" for model and many other jobs around house, farm and keeping my old Land Rover going.? Find it good for repairing foam model's, better than Gorilla as it is white. Clear also now available.

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Thanks JD8 for the thumb's up for the glue, I'll get a tube of clear.

 

Not sure if its a time thing or that fact that the previous owner stored and transported the the fuselage and center wing section as one, but there is a lot of engine weight and its very easy to put your fingers where there is no internal support. The horizontal stabilizer seemed to have some movement so I put my thumbnail between the ABS joint surfaces and just unzipped the lot! To the point that it was no longer attached apart from the elevator rod. 

 

If you look in the photo you should be able to see the horizontal stabilizer should sit and be glued to the wood formers, I think some triangle balsa need to go there and I'll always transport it in 4 parts.

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IF the tail is not well attached could you completely detach it and then put it back on properly? It might require a little work to make good the visuals but its better than it dropping off. 

 

Air retracts. Folk obsess about leaks, i dont. My test is simple. Pump up to around 85psi, wait 5 minutes, retract gear, wait 15 minutes. If they come down again and then go back up, and come down, it passed.

 

I work on the basis that 5 minutes covers start up and power checks, 15 minutes is plenty of air time, and still they came down. If the last retraction was a little soft i repeat the test with 100psi. On my P39 i had to use 100psi and add a 2nd tank as the 3 retract units and long pipe runs sucked pressure even with no leaks. This gave weak retraction on takeoff once the airflow got to work on the doors. 

 

Leaks can actually be an advantage as models with air retracts have exploded on occasion when left in the sun with a fully pressurised tank. A little leak is like a pressure valve!

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Ron, Do you expect any leak rate or just the air it uses to cycle the gear up and down. What do you normally land with pressure wise or how many cycles do you expect.

 

Once I have got rid of all he leaks I'll cycle them up and down and see how many operations I get and at what pressure they won't travel and lock on the bench.

 

Gorilla clear on order... to go with the brown I already have. ?

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When first using air retracts I expected them to be totally leak proof but soon realised that, as Jon says, as long as I can get 2 cycles (up/down, up/down) from a fill then I’m OK with it. On the TC, with a single tank and 100 psi I can get 2 cycles, a 3rd would be a bit iffy. My procedure is fill retracts, start one engine, start the other then taxi out, it never sits there for long after a fill / top up. If I was really worried then I would fit a second tank.

On other ‘planes with 2 retracts (tail draggers) I can easily get 4 cycles.


For me the second ‘up’ is the most important as that would probably be due to an emergency on a landing circuit that required a wheels up belly landing.

 

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Number of cycles is often quoted as a measure of air retract integrity but its pretty much meaningless as you will have no cycles if all the air leaks. As Ron suggests, having sufficient air to get the gear up a 2nd time is good for the reasons he mentions but once the down locks are out landing on floppy unretracted gear is not a big issue as they fold immediately. Its not ideal, but not a show stopper either. 

 

While true for all retracts, with air its important not to force the gear up. If a leg wont lock up, land and find out why. Inverted flight to try and force the gear up is a guaranteed way to jam it in the up position and is not recommended...ask me how i know ? 

 

If you are really worried about it you can get a gadget that will automatically drop the gear in the event of the tank pressure dropping below a certain value. This is fine for a slow leak, but would be useless if a pipe came off. Its also another thing to carry on the model so i dont bother. 

 

Although impossible on the cat, i always try and keep the air tank in the wing so it and all the retract gubbins are together. This eases maintenance as i dont have to have the fuselage flopping about all over the bench while i am working on the gear. 

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Good call Jon regarding the pipework installation as my tank is in the fuselage and in a pain in the backside and I have seen others with it on the top of the wing so may well go for that.

I like the idea of the auto gear down device, but for your reason +  by its very nature of deployment (at the worst possible time) I will just stick with as is. Would be nice to have telemetry to warn and then I can make the decision to gear down or not.

 

Progress has been slow as I have decided to make a stand (yoke) so I can practice gear up/down without risk of damage to U/C and more importantly doors etc. This will let me progress the tail gluing job, but there is one issue. All this needs to be carried out on the kitchen table so I need to pick a suitable time once some flying conducted 

 

It came with a couple Life rx batteries, charged, discharged and recharge and all look ok. I'll do a load test on them, but does anyone have experience with this type based on the fact these are + 6 years old (kept in a cool dark place) and had 50% charge when I got them?

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‘Old’ batteries with an unknown heritage? Use them on something else and get new ones for the TC, it’s too nice a ‘plane to risk for the sake of a few quid.

Air tank on the wing? You’re still going to have to connect air system because of the front leg! It’s no great hassle to connect the air lines, no real difference to servo connections! On that subject, on mine I use SBus and have 1 4 channel converter in each wing (2 flap servos, 1 aileron servo and 1 throttle servo)The SBus feeds are Y lead connected so that I only have 1 connection to make to the Rx. Having said all that, I store my TC with the centre wing section connected to the fuse and the wing outers stored separately, that makes connections (or lack of) dead easy. (Old photo attached)

 

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Circumstances have changed for the next few days so hopefully I'll make some progress with the Tigercat now that Jon has swapped the crankshaft bearings and given them a look over with the comment that they had not done much and the insides all looked ok. I was reminded to give them a good thrashing on a smaller prop 14x7 for 5 minutes before moving to the (now purchased) APC 15x8 props.

 

Another decision point was made thanks to Jon's experience and "what the manufacturer would say" regarding engine and tank position. The original set up puts the tank 3 inches above the center line of the carb which is clearly a no no if I ever want to get close to inverted flight and not suffer almost continuous tuning issues. With the tank moved to the bottom of the nacelle the carb is close to bottom/mid tank so not ideal or fix the problem once and for all. Rotate the engines 90 degrees and have them side mounted. IMO it will look ok from both sides, from port no sign of engines and from starboard the lovely cylinder heads of the Laser engines, rivet counters will moan that it doesn't look right, but then its not that scale so not an issue in my book. Anyway good news is that the cowl can be rotated and needs minimal work , however the recessed bulkhead will need a bit of modification to gain clearance for the carb and exhaust. I'll post some photos when I make a start.

 

While visiting Jon I popped into Motors and Rotors and picked up some "hen's teeth" UC air pipe so that's another job on the list that can be progressed

 

And lastly the cardboard template for the stand made progress on the kitchen table!

 

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 Ron, I thought Jon was being a bit derogatory about the "Yogurt pot" ASM Tigercat but you really have to see it to appreciate the skin over skeleton construction method to see that its very different to the ESM/traditional designs. The fuselage and center wing were stored together and the weight ahs split the fuselage skin where it sat on the bracket + when handling the wing/fuselage I can feel my fingers deforming the skin..anymore pressure and it will be more holes in the fuselage! Its going to have to be transported in 4 parts just to avoid damage to the fuselage, where as the wing seems a lot more robust. I suppose you don't get something for nothing and with a AUW of 17 lbs including the Laser engines it is a lightweight design.

 

PS and  no comments regarding the test lead extension birds nest on the top of the wing - all work in progress !

 

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Only managed an hour or so this evening, but am well happy with the result (plenty to tidy up) regarding the engine location.

 

They were inverted and yes I know it looks better but my mossie is a pain in the anatomy as it has to sit on the bench at WOT and put you put your hand in from behind to get your fingers burnt while adjusting the main needle.

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This works for me with tank position, just rotate the cowl and easy to adjust the main needle.

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I'll see how it goes, but might make a couple 45 degree or even 90 degree elbows to deflect the exhaust gasses 

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PS I do have some dummy engines, but I'll see how it goes first as the exit holes are quite small.

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Chris you may be able to have the exhausts pointing down by taking them out of the engine and rotating through 180 degrees, I've done that on a couple of my models at it works fine. Alternatively you could use some flexi pipe, I've done that too and haven't even used the Laser silencer!

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Thanks Ron, the exhaust discharge is sort of the least of my issues and I have some metallic flexi pipe so will have a look at the 180 option with a 90 degree bend flexi pipe or just the defuser nozzle option. Jon made a good point about not hanging loads of additional weight off the exhaust stub and I am not keen on the complication of supporting bits of pipe to the airframe...them have a habit of working loose or falling off.

 

We have the 82dB limit and anything that reduces noise is good, conversely removing silencers will just give me more problems to solve (bear in mind the ASM ABS construction, it will drum very well I expect!).

 

Throttle servo installation, refitting the tank support and a bit of strengthening following the wood removal on the bulkhead, achieve that this weekend and I'll be happy 

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A bit of a odd week regarding progress on the Tigercat as there has been very little visible change however tasks that can be ticked off the list are:

  • Completed the stand, only MDF but in my book vital as a stable platform to build off and critical if I accidently action gear up/down while working on the model and all the damage that can happen when forcing gear up or down by mistake.
  • Sticks like Sh*t used on the fuselage split near the nose seems to have done the trick as its more stable and the glue remains semi flexible so suits the purpose here, but I don't think its suitable for the tail plane 
  • Horizontal stabilizer glued on to the ply former and around the fuselage skin with Gorilla glue which took about four goes due to size of the fuslage and rotating to get the glue into the right place
  • Engines are all in and plumbed up with the tanks in the right place
  • UC all replumbed and now seems to be air tight, however further testing will prove reliability.

 

 

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Popped up the field between rain showers and allowable run times for IC engines, said to SWMBO I would be a couple of hours...over 3 hours later. ? She said I had not been missed.

 

Bound the TX/RX, set the retract servo up and initial set up of throttle servos, got the rudder, ailerons, elevator and flaps to all going the right way and nipped out to do an engine test. Only a basic run up with no tuning apart from tick over as it still smells of the fuel with the castor in it.

 

Well please with the running so far (1 tank through) on the smaller props as Jon suggested. 

 

 

Before anyone says anything I found a problem with the starboard throttle servo wiring which was causing a blip on odd occasions, now sorted.

 

Still have a problem with the fill valve on the UC and the C of G is a bit rearward + it has two LiFe RX batteries and I am not paying +£80 just to get some more. I'll see if I can use something I have already have in stock that will fit in the nose.

 

 

 

 

 

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  • 1 month later...

The Life batteries turned out as fit for purpose (thanks Martin) and with a couple of taxi tests and an aborted re-maiden due to completely wrong wind direction on two runways the model was ready.

 

The nose wheel has quite a lot of play which makes it tricky to keep straight due to over correction and with the extended taxi testing the smell of castor had almost completely gone + the clouds of smoke!

 

Nothing left to do but turn up at the club on Saturday and assemble the Tigercat and the Dual Ace (Laser 70's). The Dual Ace settled the nerves as it has no flaps and tends to land quite quick (roll on) when the grass is very short. With a start and good warm up there was only one thing to do...get on with it!

 

Pre flight photos and video link at the bottom!

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It was really a non event, no real trim needed just needs a good pull to unstick and felt rock solid although it does tell you its +14 lbs and with all tigers, but not take liberties unless you want to be on the wrong end of its bite! Looks like a keeper and will be getting plenty more outings from now on. 

 

Apologies as we are working on a better quality video and will share once its through the editing suite

https://youtu.be/KR1V-L_tunA

 

 

 

 

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