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Seagull Mosquito Laser build

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Nigel R06/08/2018 14:43:24
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3099 forum posts
479 photos
Posted by Chris Walby on 06/08/2018 13:15:08:

Someone mentioned a Deluxe glue that has very good capillary action

Superphatic?

Chris Walby06/08/2018 15:18:39
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994 forum posts
236 photos

Nigel, Yes that's the stuff.

Richard Wills 206/08/2018 20:13:20
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178 forum posts
7 photos

Looking good, my nacelle boxes started to fall apart in the post, so I rebuilt them with epoxy and plenty of triangle strip. I didn't epoxy mine into the wings as suggested, beefed up the shear web and put a 3rd blind nut and bolt through so they remained bolt in. Glad I did made the post maiden repair much easier.

I would start thinking about getting weight forward all the way. With a pair of saito 82's I have ended up with 900g of lead plus fixings in the nose to get to 130mm. I wouldn't go any further forward than this on the cg, flies great there. I now have 9 flights on it and enjoying every one of them.

Chris Walby06/08/2018 22:22:36
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994 forum posts
236 photos

Richard, Thanks for the info, very handy.

Quick look on the web and it looks like I'll be 160g heavier with my engines so I think it will be a close run thing.

Hope you don't mind me asking but what was the AUW? + What props and spinners are you using?

Not a lot of progress tonight, lots of fiddling about and trying to find tools!

  • Wing tip cover on
  • Flap servos fitted
  • Clevis rods fitted to flaps and aileron control horns
  • Retract temp fitted and servo + throttle servo in one box

Darn! Throttle servo is on the opposite side compared to the carb, but if I move the arm around it will be centrally aligned.

Richard Wills 206/08/2018 23:09:26
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178 forum posts
7 photos

Chris, I am using the kit supplied spinners, and master airscrew 14x6 props turning at 9700 rpm. As for AUW, I am well over the box figure at 17lb 1oz. It seems happy enough at that though.

Chris Walby07/08/2018 06:45:30
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994 forum posts
236 photos

Thanks Richard, that's got me thinking as the Laser prop range is 12×7-8 13×6-7 14×4-5 so depending on ground clearance (and yours is okay on 14's) I could go 14x4 if it looks okay.

I have a pair of ali spinners as I seem to get prop creep with the plastic ones and I could hide a couple of chunky spinner adaptor nuts if C of G is rearward.

I was looking at the tail wheel, very nice, but must pull the C of G back Has everyone used theirs?

Danny Fenton07/08/2018 08:10:44
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9186 forum posts
4038 photos

I ditched the tailwheel on my second one, too heavy and at the wrong end of the model!

Both of mine came in under 7kg around 14.5 lbs with cells.

I used the supplied spinners and 17 x 12 apc props

Cheers

Danny

Jon - Laser Engines07/08/2018 08:32:58
4825 forum posts
180 photos
Posted by Chris Walby on 07/08/2018 06:45:30:

Thanks Richard, that's got me thinking as the Laser prop range is 12×7-8 13×6-7 14×4-5 so depending on ground clearance (and yours is okay on 14's) I could go 14x4 if it looks okay.

I wouldnt drop to 4'' pitch. Your pitch speed will be very low and the model will feel like it has no power. 13x6 is the best start point for the engines. After an hour or so you can try a 14x6. It wont rev as fast as the 80 will spin them but it might be ok.

Chris Walby07/08/2018 09:03:01
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994 forum posts
236 photos

Thanks Jon, I was only going by the Laser website and thought you might chip in with your experience, cheers.

13x6 or 14x6 will probably work well when it comes to the noise test. I don't think the 12x8 suit the Dual Ace but it got it through the noise test (noisy nacelle covers and low ground clearance) so it is what it is. Once the 70's are in the Mossie I'll noise proof the nacelle covers and extend the U/C and try the noise test again with something less pitchy.

On the subject I weighed the tail wheel and it comes out at 51g which is worth considering its omission as its so rearward.

Edited By Chris Walby on 07/08/2018 09:23:18

Jon - Laser Engines07/08/2018 10:27:02
4825 forum posts
180 photos

13x7 should be quiet as well

Richard Wills 207/08/2018 12:56:52
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178 forum posts
7 photos

I am going to try higher pitch props next, have a pair of 14x8's I can test. Feels like it's a bit 'low geared' on the 6's.

Edited By Richard Wills 2 on 07/08/2018 12:57:11

Chris Walby07/08/2018 13:46:01
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994 forum posts
236 photos

Richard, Only personal feeling, but I find high pitch props hard work at low speed (landing). It seems a bit of all or nothing, like harder to deal with just when my workload is at a maximum.

Just me but I like a larger diameter less pitch setup, not sure about other peoples views with more experience?

Jon, I'll buy a pair of 13x7 for starters wink

Denis Watkins07/08/2018 14:02:19
3911 forum posts
61 photos
Posted by Chris Walby on 07/08/2018 13:46:01:

Richard, Only personal feeling, but I find high pitch props hard work at low speed (landing). It seems a bit of all or nothing, like harder to deal with just when my workload is at a maximum.

Just me but I like a larger diameter less pitch setup, not sure about other peoples views with more experience?

Jon, I'll buy a pair of 13x7 for starters wink

Agree Chris

As a rule of thumb for choices, go to pitch being approx half the diameter

E.g, 10 x 5, 11 x 6, 12 x 6, 13 x 7 do feel less agressive

Jon - Laser Engines07/08/2018 14:22:40
4825 forum posts
180 photos

i tend to work on the basis that 50-70 engines like 5-7 inch pitch. 80-100 tend to be better on 6-8 and anything over 120 is 8 inch as a starter. Really big engines go up to 10 inch easily.

In general it runs hand in hand with rpm. Small engines rev faster so lower pitches give the same pitch speed when all is said and done.

For warbirds i aim for 50-60 mph pitch speed as this seems to give a realistic performance.

Richard Wills 207/08/2018 14:27:46
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178 forum posts
7 photos

Chris I do find that pitch can affect landing considerably, depends on the airframe to a large extent whether it has flaps or is otherwise draggy. The Mossie has fairly generous flap and needs a significant amount of power on on the approach, so shouldn't be really affected too badly. Best compromise for the whole flight I suppose.

Chris Walby07/08/2018 22:53:59
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994 forum posts
236 photos

Update time smiley

But first the disclaimer... I am measuring up and seeing what goes where, so bracing screws, fixings and elastic bands will not be used in the finished article!

Tank position relative to carb.. that will do nicely wink

20180807_191632.jpg

So this leaves me with a question, do I cut a hole in the cowl for the cylinder head, exhaust and carb to poke out of (red option) or cut from the underside of the cowl exhaust stubs to just in front of the rad intake and then make a removable panel (with a hole in that) (green option)

Am I making any sense?

20180807_191117.jpg

cowl options.jpg

PS glued the horizontal stabiliser on the fuselage, just to show a bit of progress!

Jon - Laser Engines07/08/2018 23:05:22
4825 forum posts
180 photos

Green option is more work but will look neater all told. Its also likely to make fitting the nacelle covers and general maintenance a great deal easier long term.

Danny Fenton07/08/2018 23:17:47
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9186 forum posts
4038 photos

Keep in mind the nacelles will get a bit floppy if you cut them too much There is no structure to support them.

Chris Walby08/08/2018 08:18:39
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994 forum posts
236 photos

Red option

  • Retains maximum strength
  • Should looks better as just bits that need to be cut out will be showing
  • Can be nibbled stage by stage to get required size
  • Once done, can't do green option so would need to make new panel

Green option

  • Cut panel out with easier access to engine
  • Removed panel can be nibbled for required size + scoop/deflector if more cooling is required
  • More work, but less fiddling
  • Only visible cut lines will be the vertical ones
  • Might end up all floppy!

Notes

  • Cowl will have to come off to adjust the slow running, so once in a blue moon
  • Main needle is accessible with either option

I think I need a pole on this laugh

PS what's the best way of cutting straight lines with a Dremel?

Jon - Laser Engines08/08/2018 08:26:25
4825 forum posts
180 photos
Posted by Danny Fenton on 07/08/2018 23:17:47:

Keep in mind the nacelles will get a bit floppy if you cut them too much There is no structure to support them.

 

When Chris brought his in i noted they were about 1/8 thick fibreglass! They were really solid, im pretty sure cutting them wont matter in this case.

As for straight lines just use a fine dremel cutting wheel and go easy on it. OIf it all ends up a bit sloppy you can glue thin strips of ali sheet onto the hatch that extend to cover the cut lines. Paint them grey and noone will ever know the horror that lies beneath 

Edited By Jon - Laser Engines on 08/08/2018 08:29:14

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