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Engine for largish cw Cub

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Braddock, VC02/04/2019 16:50:22
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1633 forum posts
82 photos

I have an 80ish wingspan clipped wing Cub that weighs 7 lb ish. Currently powered by an old laser 100 that gives it about a 5 yard take off run.

The box says it suits a 90 -120 4 stroke, model dates back to the early 90s at least.

I'd like to fit a laser 80 that has very few hours on it will this be adequate do you think?

Jon - Laser Engines02/04/2019 16:54:14
4855 forum posts
180 photos

Yea, swing a 15x6 and the 80 will be fine

Braddock, VC02/04/2019 16:55:45
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1633 forum posts
82 photos

Thanks.

Paul Marsh02/04/2019 18:47:08
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3727 forum posts
1057 photos

Is it a Modeltech one? I have a 80 inch clipped wing Cu powered by a 160 flat twin, which goes well...

Braddock, VC03/04/2019 20:53:16
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1633 forum posts
82 photos

Hi Paul, I think it is.

I think yours would be far too powerful for me, I'm getting too old to fly hotrods.

Tore Sandal07/04/2019 21:34:32
17 forum posts

Hi,

one of my friends had a Great Planes Cub - 76.5 inches and around 7 lbs. It flew beautifully with an O.S. FS-52S. Plenty of power for scale flight including simple aerobatics (loops, Immelmanns, stall turns and such). Your Laser 80 will pull your Cub effortlessly.

Braddock, VC17/05/2019 16:44:24
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1633 forum posts
82 photos

Cut a long story short, bought another YT Cub, an artc kit. Some covering has been applied, the wings and fuselage are covered in white solartex, the remainder is bald.

As white solartex is like rocking horse pooh I spent a morning googling and, true to form, picked a model that suggests the availability of white solartex!

I have some blue solartex of nearly the right shade so will strip the fuselage and salvage the white solartex to cover the tailplane and struts. Then I'll cover the fuselage with the blue solartex I've had waiting for a rainy day.

I spent part of the morning making up adaptors so I can easily swap engine mounts if need be.

g pooh pix.jpg

Edited By Braddock, VC on 17/05/2019 16:45:04

Edited By Braddock, VC on 17/05/2019 16:46:35

Braddock, VC17/05/2019 16:51:50
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1633 forum posts
82 photos

One of the issues I have with this model of the Cub (it also affects the world models' version) is a stress raiser right where the aft fuselage joins the front half, just under the t/e of the wing.

Our strip is quite bumpy and tufty and a couple of planes, particularly the wm cub have tripped up and whiplash has snapped the fuse where this stress raiser is, I'll try and get a couple of pictures later.

I have a cunning plan to reinforce the strength of this area and will show it as time goes by.

Braddock, VC17/05/2019 17:20:36
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1633 forum posts
82 photos

Just weighed all the components and, gulp, 10.5 pounds with the laser 80, 10.8 pounds with the laser 100.

Will 10.5 pounds (say 11 with fuel) be too much for a laser 80?

Braddock, VC17/05/2019 17:24:15
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1633 forum posts
82 photos

Looking back, I think I should be alright, I flew the Brian Taylor Hurricane with the same laser 80 and it flew fine, I think the weight wasn't quite as much but hey, it's a cub.

Don Fry17/05/2019 19:30:00
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4065 forum posts
47 photos

Jon, will be restricted for elbow room in his new house, so to save him trouble, worn out that he is producing all those new engines, the 80 will produce sufficient power, as Rolls Royce used to say.

Tony Richardson17/05/2019 19:42:25
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605 forum posts
25 photos

I'm always amazed at how large a diameter prop a Laser engine will swing for its size, never owned one still waiting for the 180 Gasser.

Jon - Laser Engines17/05/2019 20:04:06
4855 forum posts
180 photos

i use an 80 in my 9.5lb hurricane and get scale performance at half throttle. I also flew a 90something inch black horse cub using our 100 (not my model) and had a hoot with it. Use a 15x6 and the 80 will be fine.

Tony, we are all waiting :'(

Jon - Laser Engines17/05/2019 20:06:02
4855 forum posts
180 photos
Posted by Don Fry on 17/05/2019 19:30:00:

Jon, will be restricted for elbow room in his new house, so to save him trouble, worn out that he is producing all those new engines, the 80 will produce sufficient power, as Rolls Royce used to say.

Im also in a bad mood as it started to rain just as i was ready to plant my new triffids. As i didnt want to leave them strewn all over i went for it anyway and got soaked >

Percy Verance17/05/2019 21:01:05
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8108 forum posts
155 photos

I'm not in the least bit surprised a 7lb Cub was lively with a Laser 100 up front. I flew my 13.5lb 1/4 scale Cub on a Laser 100 with ease......

A 7lb 80 inch span Cub will be fine on a Laser 70, never mind an .80......

Braddock, VC17/05/2019 21:05:02
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1633 forum posts
82 photos
Posted by Percy Verance on 17/05/2019 21:01:05:

I'm not in the least bit surprised a 7lb Cub was lively with a Laser 100 up front. I flew my 13.5lb 1/4 scale Cub on a Laser 100 with ease......

I've refreshed that, all components weigh 10 1/2 pounds, say 11 by the time fuel is added.

Denis Watkins17/05/2019 21:12:09
3914 forum posts
61 photos

Even a regular 80 4 stroke can develop the 1100W required

And a 90, something like 1300W, so a 100 is Above ballpark power

Braddock, VC20/06/2019 12:58:52
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1633 forum posts
82 photos

img_0212.jpgimg_0211.jpgimg_0210.jpgimg_0209.jpgimg_0207.jpgimg_0206.jpgimg_0205.jpgStarted putting the electronics in, here's a pictorial of how I lengthen my servo leads.

Braddock, VC20/06/2019 13:05:24
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1633 forum posts
82 photos

img_0214.jpgManaged to screw that up, basically what I do is take the connectors off both the servo and extension lead where the servo lead plugs in then solder them together , two layers of heat shrink tube over and bob's your uncle.

I also check them out on a servo tester to make sure they work.

The leads are the cheap HK ones which, tbh, tend to cause problems where the pins of the lead slip under the plastic stops, this way there is no problem.

 

img_0213.jpg

Edited By Braddock, VC on 20/06/2019 13:07:43

Braddock, VC21/06/2019 15:51:50
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1633 forum posts
82 photos

Prior to joining the wings I've just spent about 4 hours fitting in 7 off 6mm blind nuts, drilling the wing for the locating dowels, kit is so old that these were imperial, don't have an imperial drill in the house! Then drilling the wing to put the retaining screws in.

Got to dig out the drilling jig for the control surface hinges, 4 in the fin/rudder, 6 in the tailplane/elevator and another 8 for the ailerons, then I can cover those parts that aren't covered, just the fuselage and wing halves are covered in white solartex can't get ahold of anymore so using world models lightext. I'll not be able to notice when it's flying, just deep down inside I'll know.

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