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Who Else Wants a 63" Lavochkin La7 kit?

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Tim Flyer17/05/2018 12:29:31
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737 forum posts
107 photos

Thanks Bob . Maybe that one is faulty . I bought them last Nov though. The ones I’m replacing them with will need a bit more wing cutting as the motor is integrated into the aluminium casing (should be strong). They are rated for 10-12kilo planes and although a bit hefty at 170+ g each I have had no issues from them on the P 47 I thought it a good idea to keep my retract units the same units which at least will provide spares..Out with the Dremel tonight!

Edited By Timothy Harris 1 on 17/05/2018 12:30:09

Tim Flyer19/05/2018 15:45:33
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737 forum posts
107 photos

2d01cc64-40de-4925-9d7c-3d3e61596b32.jpegNow just waiting for retracts. I think balance is spot on . No lead needed 😊😧

Bob Cotsford19/05/2018 16:21:46
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7320 forum posts
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That does look the part Tim. Very nicethumbs up

Tim Flyer19/05/2018 19:24:29
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737 forum posts
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Cheers Bob thanks for your kind comments. I hope all well with you. The finish certainly isn’t perfect plus I have made a few stand off compromises as it’s the first Warbird kit I have properly built but I’m pleased with it as I did my best😊. I painted the number stickers with light grey as per cockpit as I preferred the slightly less red and white look.

Tim Flyer07/07/2018 17:27:09
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I had my second flight on my LA7 today . Unfortunately it was disappointing. My LA7 seems seriously overweight and under powered. It weighs about 4.8kg so just shy of 10.6lb and I think it needs much more power than the 80FS I have in it. I think it’s my over the top heavy building. It  took off very slowly in the light wind it only gained much speed with gear retracted. and it flew heavily and was quite a handful to land . I tried pulling out on a landing where I was too close to the edge of the runway but didn’t make it as it stalled (luckily damage minor due to heavy building !!)With the under powering it takes quite far too long to accelerate and flys very sluggishly. I think it needs at least a 100 or 120 FS, but unfortunately my firewall is too far forward to accommodate a longer engine. To increase the engine size I would need to move the whole firewall back so serious work. I’m going to leave it for now and get on with the hurricane! Anyway build it light if you have the chance still !

Edited By Tim Harris 1 on 07/07/2018 17:34:52

Jon - Laser Engines07/07/2018 19:50:36
3915 forum posts
151 photos

My Hurricane was 10lbs and was an over powered meteor with my laser 80 so im really surprised you are having trouble. Which prop are you swinging?

Tim Flyer08/07/2018 08:52:00
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737 forum posts
107 photos

Hmm thanks Jon I just reweighed it ( having to use kitchen scales) and it’s 10.8 lb or 4.9 kg.. I’m using a 14x6 APC as is still running in.

Tim Flyer08/07/2018 08:57:04
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737 forum posts
107 photos

One problem I did have Flying it was that the rudder cable was too slack( should have tightened before flight! ) so that I think caused a left to right tail waggle which might be adding to the problem of lack of speed.

RICHARD WILLS08/07/2018 09:35:02
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368 forum posts
44 photos

Hi Tim .

I think Jonathan is on the right track here , Given the large wing area of the La7 -63 , it is normally a very forgiving model . In fact on one test flight that I carried out for a friend , a conrod pin snapped and I did a complete circuit of our field with a windmilling prop , almost as if I still had power . If you watch the you tube film made by Brian Brassey and his grandson (It has the music of Boney M -Rasputin !) you will note how tame the model is and how slow it flies.

The ones I have flown have all been 91 or 120 powered but they dont require full throttle just to fly . I would guess your 80 will need to be on top form and it clearly isnt yet , 9ilb is a more typical weight but the extra will be easily accommodated .

See what Jon suggests for rapid running in and the correct prop .before doing anything more drastic .

Ron Gray08/07/2018 09:42:16
917 forum posts
231 photos

How many minutes run time has the engine had Tim? The only reason for asking is that both my 80 and 100 seemed really underpowered when I first flew them, the 100 in particular (14x6 APC). However, during the last flying session the 100 suddenly, mid flight, took on a different character and was hauling the 'plane around as though it had found another gear. I could only put this down to the fact that it had then had about 50 minutes of run time and it had started to free up, but boy what a difference, I have now got a range of different props (thanks Cosford show!) to try with it to see which suits it best for the U Can Do - 14x8, 15x6, 15x8.

RICHARD WILLS08/07/2018 09:47:06
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368 forum posts
44 photos

BTW , keep in mind that this warm weather will make all of your planes stall early as the air has lost a lot of density .

This phenomenon was clearly demonstrated in my days as a short board windsurfer (sorry about the necessary diversion) . We would use a hand held windspeed anemometer to decide which sail to use . The aim being to go for the largest you could hang on to . For a 20 mph wind in the winter you would use 5.5sqm sail. For the same wind in the summer at least a 6.5sqm sail would be required to keep the board planing .

So if anyone is beating themselves up about stalling short of the runway , go back the next morning before it gets hot , and do exactly the same approach . I bet it turns out fine .wink

Richard

Jon - Laser Engines08/07/2018 10:05:34
3915 forum posts
151 photos

10.8lbs is pretty porky so if you can find some way of removing a little beef then that would be good. That said, the 80 with a 14x6 should be doing 9k plus and while you might not have much vertical due to the weight straight line speed should be good. In general our engines tend to give all they are going to more or less from the get go. Just forget the running in, thrash it to within an inch of its life. I promise you, you wont break it.

Flying style may also be a factor. With a heavy model it wont accelerate that quickly so if you are tight on your turns etc it will feel like its dragging its backside around with no real go. See what happens if you make really smooth/sweeping turns sacrificing height for speed and then turning speed into height to repeat the process. You will find that momentum is your friend and its a good thing to practice as the big Hurricane will need to be flown this way as well.

I also agree with Richards comment about the hot weather. My nieuport is like a pig on a skateboard when its really hot. It likes air so thick you can chew it!

Bob Cotsford08/07/2018 11:55:22
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7320 forum posts
419 photos

Ron, I ran my 100 on a 15*6 APC, I would have thought a 14*6 would have it overreving.

Edited By Bob Cotsford on 08/07/2018 11:56:22

Ron Gray08/07/2018 13:21:28
917 forum posts
231 photos

@Bob - the 100 I'm using is not the one I got off you, it's a new one so the plan was to run it with the smaller prop to rev the nuts off it whilst running in. I'm planning on the 15x8 for aeros but will go through the 14x8, 15x6 first to see what happens. I also have a 16x6 to try out as I don't need speed but do want grunt.

RICHARD WILLS08/07/2018 15:11:58
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368 forum posts
44 photos

You can build the bigger La7 very light , but to put things in perspective , ask anyone who has built a Topflite warbird of similar size what it weighs .....

It will make you feel a lot better about your 10lbs.

Tim Flyer09/07/2018 11:24:44
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737 forum posts
107 photos

Cheers for replies chaps . Yes it certainly was really hot and noticeably thinner air as I really struggled climbing on takeoff until the gear was up. It was certainly tougher than the maiden flight in cooler weather. The flappy slack rudder did have a slowing effect too as I believe the balancer section on the front was catching the air causing it to weave laterally. I will soon fix the rudder. It was the engines second time in the air and it was tuned for max rpm . I think the big spinner as well as alm the weight and drag from the rudder was just too much. I have noticed the laser 100 is the same length as the 80 and it looks like similar exhaust dimensions, so all I will need is a bit wider engine mount and possibly a bit of cowl cutting. I can’t really loose weight unless I used lighter retracts so I think when available I will squeeze a 100 in 😉

Edited By Tim Harris 1 on 09/07/2018 11:27:42

Ron Gray09/07/2018 12:59:11
917 forum posts
231 photos

Tim, I have a 'spare' 100 which you are more than welcome to borrow to give it a try in your LA-7 if you want to. When I swapped my 80 in the U CanDo for my other 100 all I did was to use another adjustable engine mount, no other changes were necessary.

Tim Flyer09/07/2018 14:52:40
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737 forum posts
107 photos

After having a really good chat with Jon he explained further that it might be better to give it another go rather than use the “cheque book approach” and buy another engine . He suggested doing that and winding up the speed during flying. There is certainly more power available in future in the 80 than I currently have and with the rudder fixed I should get much more speed. I will also experiment with props. Once run in I would normally increase pitch anyway. On my Spitfire I use a 14x7 on my Laser 80 so I might try that and a 15x6.

Tim Flyer10/07/2018 09:28:18
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737 forum posts
107 photos

Sorry Ron I didn’t reply as missed your kind offer but if your 100 is available I would certainly like to buy it if it’s in good condition as I’m sure it could go in another plane even if I don’t put it in the La7. I have sent you a PM

Ron Gray10/07/2018 10:01:36
917 forum posts
231 photos

Ah, me selling a Laser, I only collect them! Sorry Tim I don’t really want to part with any of my Lasers in fact collecting them has become a bit addictive!

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