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Seagull Mosquito Laser build

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Chris Walby18/08/2018 22:41:21
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1000 forum posts
236 photos

Ronos,

Looks like your engines might be a tad heavier than mine wink Have you tried your c of G yet?

I had mine up on the stand with the C of G as below

20180817_170650.jpg

Then thought to myself how about some brass nuts!

20180818_175835.jpg

Result should be something like this

20180817_181449.jpg

Rotating mass has increased by 25% and its added another 135g overall to the weight of the model.

I'll stick with this until I have everything in and finished and then see what to do with the tail wheel assembly.

PS Not machined brass in 25 years...forgotten how much noise it makes wink

Ronos18/08/2018 23:20:23
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170 forum posts
17 photos
Not yet Chris, just doing a dry run, making sure everything fits, then when she's ready to go, I'll do a final check, loctite everything that can move, then check c of g at 130mm, then put it to bed until I grow a pair, haha.
Ronos18/08/2018 23:29:30
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170 forum posts
17 photos
Here's a question, just noticed on your photo that you are measuring the c of g on the underside, not with the model upside-down is there a reason for this, is it because the wings are in the middle of the fuselage. Any models I have had high wing measured the right way up, mono wing measured upside down.
trebor19/08/2018 09:29:57
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1907 forum posts
214 photos

That's an interesting CofG stand ? I haven't seen one like that before.

Ronos23/08/2018 21:48:58
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170 forum posts
17 photos

dsc_0297.jpgsorry to hijack your thread Chris, but thought I would show where am at in my build. One cowl to cut and fit, and C of G and weight to check. How are you getting on with yours? Close to the maiden.dsc_0298.jpg

Chris Walby24/08/2018 06:29:19
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1000 forum posts
236 photos

Trebor, Sorry can't take any credit for the stand as its the cub's and is a real bonus compared with trying to hold a 6KG model on fingers! Very handy as it allows plenty of time for me messing around with the C of G.

Ronos, no problem with a couple of mossie photos wink

You will probably have finished yours before I get the engines in mine as I am still messing about with the cowls and beefing up the nacelle box.

Did you epoxy your nacelle boxes into the wings?

Ronos24/08/2018 07:52:42
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170 forum posts
17 photos
Hi Chris, yes I did epoxy the nacelle boxes in after I beef them up with cloth and epoxy resin and a couple of cable ties (just in case), didn't quite fancy the small lips on the back and two screws to hold it in place.
Jon - Laser Engines24/08/2018 08:29:14
4836 forum posts
180 photos
Posted by Chris Walby on 24/08/2018 06:29:19:

You will probably have finished yours before I get the engines in mine as I am still messing about with the cowls and beefing up the nacelle box.

And waiting for me to send him the engines im working on it, dont panic!

Chris Walby26/08/2018 09:11:55
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1000 forum posts
236 photos

Good news I am making progress, but don't have much to show for it!

More on the wiring, problems with the RX and a my decals turned up.

Huston I have a problem!

I have a very nice set of nomenclature with everything from "Trestle" to "Engine oil main header tank" but no guide as to where to put them. I have pored over my photos of the Duxford and DH museum mosquito photos + a good dose of the internet with not much luck.

Does anyone know if there are any specific guides or photos of where to place them... I have managed to located about 15 of the 45 I have.

Thanks in advance

Chris Walby26/08/2018 22:17:02
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1000 forum posts
236 photos

Again more progress today with the nacelle boxes epoxied in and fuel proofed + the wiring loom finished.

I have put my donor 70 back in the speed air as the 70 pair are imminent for install.

Better get on with some pilot painting then !

Is it me or do the machine guns look the wrong scale and have Seagull misplaced the cannons? surprise

Chris Walby31/08/2018 22:51:47
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1000 forum posts
236 photos

More progress today with the engine and tank install complete + a load of the little bits and bobs.

Up to the field for a check over, C of G and engine run up.

I still have the pilot to finish painting, but the C of G comes out at 130mm wheels up and very little chage with wheels down.

20180831_164418.jpg

So very happy with this

Less happy with my RX issue and my inability to set the throttles up the same...but at least both engines ran up with no issues.

Couple of questions for the other owners

  1. Mine seems to have a lot of fore and aft movement between the wing and fuselage and looking at the wing bolts the inner fuselage flexes an fair bit
  2. Does anyone know what the thread is for the wing bolts and I need to tap a tight one out?

Danny Fenton31/08/2018 23:54:48
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9213 forum posts
4063 photos
Hi Chris, if your wing bolt issue is the same as i had on mine, it was cured by gluing some large 1/4 ply washers to the inside of the fus. This just packed out the screws and completely sorted the issue. I also shortened the bolts a little just so that they were quicker to fit.
Cheers
Danny
Chris Walby01/09/2018 07:24:59
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1000 forum posts
236 photos

Thanks Danny, I had the same idea and will shorten the bolts up at the same time.

I tried some Vaseline and one is still very very tight. It looks quite a course thread so I don't think its metric. The one on my other Seagull is a UNC if I remember correctly (I used some bolts out of my dad's collection of BSF, Wit, UNC and UNF) ! Its not very time efficient searching through loads of old marmalade tins where the masking tape has faded beyond recognition, but I do find the odd gem where it shouldn't be! 

Photo below won't post last night (technical issue), but as you can see its getting close!

20180831_163415.jpg

Edited By Chris Walby on 01/09/2018 07:29:46

Ronos01/09/2018 12:36:52
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170 forum posts
17 photos

Hi Chris looks good in the sun, when's the maiden? Danny thanks for the fix on the wing bolts, I'll keep a eye on that. Took Richards idea and fitted two Slec fuel tanks. Trimmed back to retracts and then nibbled away at the front until they slid in.dsc_0306.jpg

Chris Walby05/09/2018 07:12:54
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1000 forum posts
236 photos

Ronos,

Nice mod with the tank (wish I had taken the plunge and removed that much of the box) although my bulkhead is further back/throttle linkage passes through the void.

General update:

  • Pilot painting has been subcontracted to my daughter with a more artistic touch than me
  • Wing fixing ply washers to me made and installed
  • Bought a new RX to resolve the range issue (Spektrum/Lemon thread if interested)
  • Wiring loom

Personally (with myself) I have a problem with a using JT-XH connectors after a comment about my "miss use" of them. I thought the comment was inappropriately harsh in its bluntness, however following some testing I have found issues with them.

This coupled with the aggravation of setting the engines up by adjusting the grub screw on the servo for each one, I have to pick it up off the ground and invert it on the bench then fiddle about.

I have ordered some recommended 6 pin connectors, will have to use servo connectors for the wing lights.

Good news is I have almost cracked the dual throttle channels, throttle cut, failsafe issue so will use the 8th channel and have independent throttles I can trim on the TX (yes I know others suggested it and now I know why when the linkage is so hard to get to!).

Jon - Laser Engines05/09/2018 07:56:08
4836 forum posts
180 photos

when setting up twin throttles I make sure the throttle arms on the carbies are in the same place, and obviously make sure the servos match. All I do then is connect the throttle rods up with the servo and engine held at full throttle. If the carbs are open against the stops they have to be both exactly the same.

I then nip up the adjustors and im done.

Once the engines have run I may then screw/unscrew the clevis at the engine end a turn or two for fine tuning but in general I tend to keep things simple.

Chris Walby05/09/2018 08:55:41
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1000 forum posts
236 photos

Hi Jon,

I see where you are coming from and I had no trouble with the new twins in the Dual Ace as the rods are accessible and have a clevis on the servo arm.

I have made a rod for my own back (no pun intended) by going with the Seagull (thin rod, tube and barrel on the servo arm. As I have committed to new plugs/sockets on the wiring loom + sorted the additional throttle channel in the TX out, I might as well do it all now.

The alternative is replacing the throttle rod and I really can't be arsed with taking the cowls off and engines out to do it (not if I can do it with a couple of soldered wires).

I spent Sunday up at the field and they are real close, but its a fiddle lifting a seven and a half kilo model onto the bench upside down and adjusting the barrel grub screw.

I did the gear on separate channels and it was a doddle to set them up with different end points on the TX (still don't like mechanical retracts, but these are nice).

Ronos05/09/2018 20:55:26
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170 forum posts
17 photos

hi Chris, first time out of the loft. one engine was low on tick over,but with a bit of adjustment got them running together. Still needs a bit of fine tuning,dsc_0303.jpg

Chris Walby06/09/2018 22:55:04
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1000 forum posts
236 photos

Still making progress here as the weather is not so good and work in very busy, anyway wiring loom finished and tested with the new plugs + 8th channel used for the other throttle output.

20180906_222510.jpg

And the pilot close to being finished

20180905_222650.jpg

Need to head back up the field for more checks and the noise test on Saturday.

Martin Harris07/09/2018 00:51:45
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8881 forum posts
221 photos
Posted by Chris Walby on 05/09/2018 07:12:54:

Personally (with myself) I have a problem with a using JT-XH connectors after a comment about my "miss use" of them. I thought the comment was inappropriately harsh in its bluntness, however following some testing I have found issues with them.

I'm guessing this refers to a comment I made in another thread - and I'm sorry if it gave offence as none was intended.

I assumed that the picture that you'd posted was of a commercially available extension balance lead but if you made it up, there's little apparently wrong with the workmanship. The point I was trying to make was that the male connectors are intended to be used on PCBs and have no strain relief built in to support the wires - hence the "misuse" comment which was, as here, in inverted commas.

I have seen too many of the commercial extension leads fail at the solder to wire junction (and even some I've made myself - shock horror!) through wire fatigue and I don't believe that heatshrink gives enough support to trust these terminations for critical components.

 

Edited By Martin Harris on 07/09/2018 00:53:17

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