Seagull Mosquito Laser build

[J D 8]

Some years ago at an air display I was chatting to a former Mosquito intruder pilot. Dam fine aircraft he said. Packed a heavy punch and was fast, got you in and out of the hot spots real quick. [ his language was a lot more colourful ]

We were watching mosquito RR299 doing its display . " Bloomin fools" he said " asking for it flying a mosquito like that at low level" .

A few years later crash it did. The investigation concluded that a temporary reduction of power of the left engine resulted in a yaw followed by loss of control into a spiral dive.

[Chris Walby]

Thanks guys for all of the helpful advice and I agree with your analysis.

In preparation to flying the Laser Mosquito (my much needed experience of running glow and flying twins) I build the pair of 70's into a SG Dual Ace. Jon's advice has been very helpful throughout the entire process, but especially with twins and the general concept of always having a plan B in case something goes pear shaped. With that I mind practiced on the simulator with various engine cut scenarios.

Just as well as my electric BH Mossie suffered a loss of a motor on a low fast pass and survived by more luck and me not doing the wrong thing!

JD 8 I have not seen the RR299 footage for quite some time, but the way mine rolled in is very similar, just I had a lot more height on my side. My passion is for the wooden wonder and there are some interesting comments from Mosquito pilots about its flying characteristics, but equally its sting if things don't go well. There were quite a few losses on take off if one engine lost power. The additional drag of the prop and low air speed combined with the urge to apply more power from the good engine would end in disaster.

A reminder to me that it is not the Dual Ace by a very long way and that the greatest enjoyment often needs a proportional amount of effort from me (and respect!).

[Jon H]

Posted by J D 8 on 25/05/2019 23:08:58:

Some years ago at an air display I was chatting to a former Mosquito intruder pilot. Dam fine aircraft he said. Packed a heavy punch and was fast, got you in and out of the hot spots real quick. [ his language was a lot more colourful ]

We were watching mosquito RR299 doing its display . " Bloomin fools" he said " asking for it flying a mosquito like that at low level" .

A few years later crash it did. The investigation concluded that a temporary reduction of power of the left engine resulted in a yaw followed by loss of control into a spiral dive.

The accident report for that makes interesting reading. In essence, neither carburettor was set up correctly and this left the engines vulnerable to lean cuts under reduced G. Suddenly loosing 1400hp from one side of your aircraft is certainly going to ruin your day

[Chris Walby]

Thanks again for everyone's input, I think I'll go for a combination of too slow over the top (tip stall) made worse by the engine imbalance at low throttle setting and a dob of cross wind as well.

The numpty on the sticks will have hopefully learnt his lesson which leaves some advice for the mechanical modification to do.

The current arrangement is quite thin wire and barrel on the end of the servo arm. What I would like is a clevis, but I am not sure the best way of fixing the small diameter wire to a threaded stud for the clevis.

Idea's anyone please

I'll take some better photos and post

PS its the servo on the right behind the wires wrapped around the oleo (removed before flight!)

 

Edited By Chris Walby on 27/05/2019 06:25:51

[cymaz]

Chris, sounds like the loop was too big. How do you prep the engines before flying? With my multi ones each engine is individually run up, tacho and pick up-checked. Then all run up together, that way you can spot a problem or discrepancy in any engine. Do not rush this and anything you’re not happy with, now is a good time to fix it at home.

When setting up the throttles I placed a small length of wire into the barrels and shut the throttle. Then set all the throttle arms at the same angle using a bevel gauge. Are your throttle servos moving at the same speed? Are they at the same position at 1/4, 1/2, throw etc.

Its a pain to get right but great to see

Edited By cymaz on 27/05/2019 06:52:50

[Chris Walby]

Thanks Cymaz, I warm each one up individually and set the main needle WOT, then run both up and check they are in sync.

My problem is that I have each servo on a separate channel with a couple of mixes in to get throttle and throttle cut to work, Somewhere in there I have messed it up and the Aux channel does not follow the throttle for the initial 0 to 35% although it catches up by 40%. Adds to the excitement of taking off and I didn't think it would make much difference in flight...I hadn't anticipated doing an inverted stall test (top of loop!). I'll do what Jon suggested (teach me!) and set them on a single channel and spend more time mechanically setting them up. Live and learn.

What I need is a simple and elegant solution that results in a clevis so I can tweak it by 1/2 turn to get them spot on.

PS I like your idea of a pin to set the throttles at the same place and that might get me close enough.

[cymaz]

Can you get Bowden cable down the tube? Then solder some threaded links on.

Or even....two of these

[Chris Walby]

Sorted the TX out and have since found a much more elegant way of doing the mix, but that's for another day.

Yesterday was all about having some real fun (although still getting used to this war bird) with the wide sweeping low pass. Climb out and perhaps a cheeky slow roll.

Tried a big loop and just kept the power on until well over the top with no issues.

"Black Rufe" on a low pass (credit to Dave for the photo)

Landing was pants, but that's just me as it sent the warning message out and I just backed off the throttles too quick, caught out by something that lands short ever weighing this much

Once again thanks to all that have given advice over the build and flight.

[Danny Fenton]

Looks great, well done Chris

Cheers

Danny

[Nigel R]

Chris,

Mossie is looking good!

Did you ever return the throttles to a single channel and have a go at the mechanical setup?

cymaz

I like the idea of locking the throttle barrels and lining up throttle arm & servo arms. Going to pinch that for my twin build when the time comes to do engine setup.

[Chris Walby]

Once I found out what I had done with the mixes in my TX and got rid of the throttle cut feature that was screwing things up (could not inhibit the knob on DX8g1) I decided to leave it as it is.

I'll need to take the cowls off and while I am doing that I change the linkage to adjustable clevis set up. Winter project!

I think I'll try Jon's suggestion of setting it up with WOT at 100% servo travel, then sub trim at shut is good advice (not that other is wrong) as I am a bit nervous of putting anything solid down the carb inlet and closing the barrel against it. Not an issue with a gentle finger, but if I forget/mess up and drive a servo against it, it may do it some harm.

PS the twin set up is super easy on my DX8g2 (with no mixes) + they are running in sync now so not an issue. Just spending more time fixing the U/C, but that's mu fault!

[Jon H]

Looks really awesome in that photo. Now i want one again

[Chris Walby]

Jon, If you don't have a pair of 70's you could drop the lead/tail wheel lump and squeeze a pair of 80's in. The bulkheads have to be moved back anyway, so it would only be the tanks needing a bit of a tweak. Don't get me wrong the 70's are more than okay, just best if kept 3/4 to full throttle to keep her hustling along.

Don't forget there's a try before you buy offer from me just in case your on the fence.... (Free with any hurrie maiden).

[Jon H]

stop it! you are a bad influence. i have a matched pair of 80's and could swap the gear from my current 70 powered twin into the mossie....but i must resist

Wont say no to a twiddle of the sticks though