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Who Else Wants a 63" Lavochkin La7 kit?

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Ron Gray24/12/2017 10:13:54
1682 forum posts
458 photos

That was my gut feeling too Jon.

RICHARD WILLS24/12/2017 10:50:19
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Ive tried it on open structures , but for me, it didnt really have the benefits you would expect .

It does go tight , but will be pierced by stiff straw .

Solartex is heavy , (probably the paint being soaked up ) , I have used light span , hard to work with , doesnt shrink much .

Solarfilm rubbed matt with a brillo pad seems to be a good compromise .

Having said that , I dont remember any of the La7s being particularly "Arsey" . I wouldnt get too hung up on weight during the build . The decider with be those that use a 4" brush with their emulsion. disgust

Ron Gray24/12/2017 11:09:19
1682 forum posts
458 photos

Thanks Richard.

Bob Cotsford24/12/2017 13:17:54
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Solartex can be heavy, especially if you try to get a shiny gloss finish on it. If you accept the weave showing through your paintwork then it doesn't need to be heavy. The pre-finished stuff, Glosstex - that really is heavy!

How does the brown paper and paint compare to eg Solarfilm, Prymol and paint or Solartex and paint?

RICHARD WILLS24/12/2017 13:54:06
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396 forum posts
51 photos

Weight wise , not much in it . My planes are always brown papered and very rarely do people make a lighter plane.

Very little skill involved , or time .

The other thing , is that brown paper impregnated with PVA forms a composite skin that ends up hard ,

Plastic films on the other hand , give very little increase in structural strength or ding resistance .

Bob Cotsford24/12/2017 22:23:34
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8248 forum posts
454 photos

I have two rolls of Sainsbury's brown parcel paper and a bottle of Wickes own brand PVA - I think I'll try the ailerons first before going for the big bits.

Ron Gray24/12/2017 22:41:24
1682 forum posts
458 photos

Don’t forget to post the results up Bob!

Tim Flyer27/12/2017 11:39:29
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1218 forum posts
231 photos

Hope all had a merry and healthy Christmas! 😊. have almost finished on the retracts now and used gorilla glue to set the boxes in . Is anyone else going to be using flaps? I would like to and that would be my next main job . However it does seem the trailing edge is very thin to try to use the required split flaps on this model . If I make split flaps I will probably need to start them about 1cm in from the trailing edge. I would be interested in seeing what others have done.

Edited By Timothy Harris 1 on 27/12/2017 11:40:13

Ron Gray27/12/2017 11:51:15
1682 forum posts
458 photos

Hi Tim. I was toying with the idea but, like you, came across the thin TE issue. I did think about making the flaps with a litho plate underside which, being so thin, would close against the TE and wouldn’t really show then I thought about how easy it would be to ding the plate. The way I’m thinking at the moment is a) does it need flaps and if so b) make them full thickness rather than split. Im tending to favour no flaps!

Bob Cotsford27/12/2017 12:14:49
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8248 forum posts
454 photos

If I were going for flaps then I'd cut of the rear veneered foam to the width of the flap and insert a balsa spar. There are two ways of doing the flaps that I considered, one using scale split flaps, the other non-scale full depth flaps. Full depth is easy enough using trailing edge section balsa bottom hinged. Split flaps would need 1/16" ply or glass sheet for the fixed top half forming the wing surface with a few supporting riblets and the same material for the moving flap, this time with a suitable section hinge spar and riblets.

I'm not bothering on mine as I don't think it will have a high enough wing loading to warrant the trouble needed to fit them.

Tim Flyer27/12/2017 13:00:45
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1218 forum posts
231 photos

Thanks chaps I think my preliminary thoughts concur. I’m probably now going to fibreglass/epoxy my wings (I’m a boat builder at heart and I do like using it 🙂 . My main reason for wanting flaps is I like having them on my planes as i find it an extra bit of fun to use them . My BH Chipmunk 60 has them as does my P47 (Laser 100) , and my World Models Spitfire 60 , so I don’t want this to be the odd one out . I also tend to build a bit heavy so it’s nice having them on a calm day when my hefty models need the extra lift . I even put flap/air brakes on my 80 powered Wot 4😊. As Bob says non scale full flaps would be easiest to fit in and would be like a mini aileron just with bottom hinging . If I use split flaps I will have to be very careful with the rear edge although fibre glass reinforcement will easily stiffen it, but the sanding will need to be very delicate. I will let you know how I get on . I don’t think I will use the litho plate though as fine epoxy/glass should be stiffer and won’t dent . Anyway I will post up once I get started. First I need to finish the retract surface blending in. Happy Building.

RICHARD WILLS27/12/2017 13:07:26
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396 forum posts
51 photos

As Ron points out , it is the remainder of the wing being left unstable that is the problem .

However if you are prepared to go stand off scale, there is a good compromise:

What I do , is get two plastic tubes from the KS metal range , They have them in most model shops, including plastic kit and train shops , plus hobby craft ,

You simply cut a trench for the small diameter tube , roughly where the flap hing line would be . Sink the tube flush with the skin . Then glue (ABS or airfix glue) a 1mm thick piece of flap sized plastic sheet onto the tube .

Make the flap 10mm shorter than the tube at either end . Then create end bearings from the larger diameter tube .

These must be gorilla ( or epoxied )glued to some scrap blocks to anchor them .

You end up with a tubular hinged flap "door" ,

I usually leave the inner tube very long toward the middle of the plane to drive like a torque rod . Alternatively you can use individual servos .

Either way , the whole process can be done in two hours .

Tim Flyer27/12/2017 13:45:41
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1218 forum posts
231 photos

Thanks Richard that sounds a very good idea too.

Ron Gray31/12/2017 13:57:35
1682 forum posts
458 photos

Started to look at the fin / rudder and came across a small issue, the rudder is bowed:

Rudder1.jpeg

Now I could probably get rid of it during the sanding process, cut a new one, make up a new one but I decided to fix it! Cut some slots into the rudder using my scroll saw

Rudder2.jpeg

Then, using ice lolly sticks (my epoxy mixers) and Gorilla Glue removed the bow.

Rudder4.jpeg

Ron Gray31/12/2017 20:50:03
1682 forum posts
458 photos

Going back to the flaps conundrum, bearing in mind that the wings, as supplied, have a potentially vulnerable TE, I was thinking that if I cut off a section of the TE of the wing I could fit a balsa TE in its place which I could then split for flaps!

Bob Cotsford01/01/2018 10:47:59
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8248 forum posts
454 photos

Sounds like the best solution if you haven't yet started the wing Ron. It works just fine on many other foam wing designs and has the advantage of being a more integrated solution, ie building in stiffness instead of adding weak points by introducing breaks in the wing skin.

This weekend I have been mostly applying filler to the fin/top deck junction and wing fillets, then sanding most of it off again.  Oh - and assembling an Easystreet 2 of course face 1

Edited By Bob Cotsford on 01/01/2018 10:51:13

Ron Gray01/01/2018 10:58:57
1682 forum posts
458 photos

You got one then Bob!

Bob Cotsford01/01/2018 11:47:31
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8248 forum posts
454 photos

off topic, sorry - yes Ron, see here

Ron Gray28/01/2018 19:30:28
1682 forum posts
458 photos

A bit quite on this thread of late but I've been busy with other projects, as no doubt others have. anyway I ordered a steerable tail wheel assembly from HK which arrived a week or so back and I've just got round to weighing it:

hujn6wghq%6oz8yhb07fxq.jpg

Tim Flyer05/02/2018 11:38:21
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1218 forum posts
231 photos

Hi chaps will post up a picture what I have done re flaps . I have built mine but will not be fixing them on until I have glassed the whole wing. I have made flaps from thin 1/16 “ (I think )ply that I have laminated with glass . They mount flat on the surface and will be hinged into a length of 1/2 inch square balsa I have glued into the wing . The flaps will have balsa fairing all round to blend them into the wing. The trailing edge will have a 5mm strip to blend it in and will also act as reinforcement. My flaps will strengthen the wing . Each flap has its own servo box which is also glass laminated. My wings will be strong 😉

Edited By Timothy Harris 1 on 05/02/2018 11:39:14

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