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Author Topic: PZL Wilga for .5cc diesel  (Read 8321 times)
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Squirrelnet
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« Reply #25 on: November 11, 2018, 12:37:18 PM »

Made a start on the wings. The core wing section seems very small with a tiny chord but the wings are a curious affair with large separate flaps and ailerons with full width LE slats both of which bring the chord up to a more reasonable looking amount.

The fuselage to cowling transition is a bit vague on the plan but I have done something that looks like the pics of the full size I have. I have added a fair bit if 1/2" balsa stiffening behind the rather vulnerable looking front former. The cowling I will make in balsa and permanently fix it to the fuselage. The engine access for fuelling , fitting and removal will be from above via a cut out in the cowling. I'll have to make a top cowling , probably out of epoxy glass. I was hoping I could do it all quickly using balsa but I think the moulded top cowl is the best answer

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OZPAF
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« Reply #26 on: November 13, 2018, 03:11:42 AM »

The moulded sheets of balsa look neat SN. It will have loads of character.

John
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billdennis747
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« Reply #27 on: November 13, 2018, 03:15:18 AM »

I think the plan blurb said it would be 'an ideal first scale model'!
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Squirrelnet
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« Reply #28 on: November 13, 2018, 03:03:11 PM »

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I think the plan blurb said it would be 'an ideal first scale model'!

Hopefully there weren't too many hopes and dreams that ended in a pile of warped balsa and riblets  Undecided

I fancied building one after perusing the APS plans book as a lad ...glad I didn't now, I went for Ron Moulton's Auster AOP 9 instead
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Squirrelnet
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« Reply #29 on: November 17, 2018, 01:35:46 PM »

Pic 1 - Another model another Redfin, this one has black fins but it's the larger 030TBR, another special order from Alex Phinn. The cowling I'll do in balsa I think so I don't have to resort to plugs and moulds - I want this to be a quick build.  I'm thinking the top removable section could be steamed 1/32" balsa with a layer of carbon tissue underneath to give it some strength.

 I've not used carbon tissue before but I remember an article in AM from a while back, I'll dig that out, anyone here used it and have any pointers

I'm keen to push on with the other project I have running, the Hawker Tomtit but one of the things I need to do is spray the wings silver. I'm hoping I can finish this one and spray it, to use it as a bit of a learning curve before tackling the Tomtit. I did spray the fuselage but there's way too much paint on it for my liking and I'd like to work on my 'technique', particularly after reading Richard's articles in AM (and well get to a stage where there's more on the model than me !!!)..  and I've bought another airbrush since as well


Pic 2 -  Work continues on the 'simple' wing construction. Flaps/ailerons are one piece with a 1/32" sheet base, then glued to the end ribs which are full width to give the shape. I'll add some joining ribs in too where the original hinges are located.

 The LE slats are 3/32" sheet which, according to the original article, is steamed round a broom handle with a doweling LE added then sanded to an airfoil.... I'll tackle that tomorrow.

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OZPAF
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« Reply #30 on: November 17, 2018, 05:46:52 PM »

Re the carbon tissue on balsa. Although I haven't used carbon tissue I imagine it would be very similar to light 3/4 oz glass cloth but more fragile.

I would consider giving the carbon tissue a light spray of hair spray to help support the fibres before cutting it out. Wetting  out on a slightly oversize piece on thin plastic(Freezer bag or similar). with another piece on top of the wet cloth.Then transferring it to the inside of your premoulded  balsa shell with the outside layer of plastic still attached, followed by placing back onto the mould/fuselage until it hardens. The outside layer of plastic can then be peeled off and the shell glued to the fuse structure.

I think this approach would work and the plastic layer on the outside would make it easier to handle without damage.

John
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Squirrelnet
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« Reply #31 on: November 18, 2018, 02:54:46 PM »

Good thoughts John thanks for that

I sorted the centre section today , the ali tube is to take an internal rubber band for wing retention. The plan doesn't appear to show it but I will sheet the top of the centre section. I spent a while making sure all is straight with incidences etc, hopefully the workshop gremlins will leave it in place while the glue dries

My brooms have been given a new masking tape and steamed balsa handle too

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USch
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« Reply #32 on: November 18, 2018, 03:33:39 PM »

...steamed 1/32" balsa with a layer of carbon tissue underneath to give it some strength.


If you want "strength", not rigidity, use a light glass-cloth (around 25g/m2) and not carbon fibre. Much easier to apply, less costly and lighter than any carbon cloth you can find on the market. As weight concerns the most important thing is to use a very fluid resina (like the MGS 285 typ), maybe even diluite it with a bit of thinner. At the end glass fibre, being less rigid than carbon, is better suited to balsa.

Carbon tissue or carbon weave is not able to follow spherical body's and if not used with a lot of care tend to absorb a lot of resin.

Just my 2 pence worth...

Urs
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OZPAF
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« Reply #33 on: November 18, 2018, 06:28:56 PM »

I think you're correct Urs. Controlling the resin content in any tissue(it's very fragile and would pull apart)
would be difficult - I would rather use glass cloth.

John
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Jez Wilkins
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« Reply #34 on: November 19, 2018, 07:56:59 AM »

USch said
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If you want "strength", not rigidity, use a light glass-cloth (around 25g/m2) and not carbon fibre. Much easier to apply, less costly and lighter than any carbon cloth you can find on the market. As weight concerns the most important thing is to use a very fluid resina (like the MGS 285 typ), maybe even dilute it with a bit of thinner.

Glass cloth can also be applied very successfully by using either 'Aerokote' (Deluxe Materials) or Nitrate Cellulose dope (both of which I have used myself).  I have also read of people using cyanoacrylate for this purpose, but have never tried this myself.

Cheers,

Jez Wilkins     
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Squirrelnet
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« Reply #35 on: November 24, 2018, 01:17:05 PM »

Thanks guys for your thoughts. I had actually pulled the trigger so to speak, on buying some carbon tissue before your replies came in so I will give it a go and report back.

It is quite robust to handle, more so than the light glass cloth I have and has a weight of just 10g/m2 . I bought some water based resin to try as well called Ezy-Kote ..hmmm two new variables.. maybe should kept that to one new thing ...  Undecided

I rigged the dihedral into the model today and although more than the scale amount it looks fairly modest to me, helped by the fact that I picked a full size example with some dihedral rigged into as well. Some I notice are rigged at zero

Wing fixing is wire dowels with an internal rubber bands holding the wings together.
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billdennis747
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« Reply #36 on: November 24, 2018, 02:00:35 PM »

It's looking very nice. Will it be yellow over the black?!?
Please don't anyone else buy any carbon tissue - I've got some I'll never use
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Squirrelnet
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« Reply #37 on: November 24, 2018, 02:21:48 PM »

Yellow indeed .. as the pic in the background.  Interior of cockpit will be black though, if that's what you meant ?

I was interested to try Carbon Tissue, have you found it to be not very good?
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billdennis747
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« Reply #38 on: November 24, 2018, 03:23:45 PM »

No Chris; I was given it but haven't tried it and doubt I will
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OZPAF
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« Reply #39 on: November 24, 2018, 06:46:54 PM »

I like the way it captures the delicate structure and all those curves SN. Nicely done. Only the cowling to go. Good luck.

John
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Squirrelnet
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« Reply #40 on: November 25, 2018, 01:43:30 PM »

Thanks John.  Bill... I'll give it a go and post the results..maybe its the new wonder material ?... Huh

 I finished off the centre section today. A bit more deviation from the plan so it looks more like the photo with the small upper window and fuselage lines continued with the 1/2" balsa top for the cabin roof. I've added a triangular fairing in front of the upper window too, as per the photo

The LE Slats have been cut from the broom handle where they were drying, cut to the right size and razor planed into an aerofoil section. Everything is just taped together at the moment on the wings as I'll cover and paint the the various bits before finally gluing it all together.





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Pete Fardell
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« Reply #41 on: November 25, 2018, 02:13:02 PM »

Lovely work, Chris; I do like Wilgas. (If it wasn't such a *****y awkward shape I might even be inclined to attempt one!)
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billdennis747
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« Reply #42 on: November 25, 2018, 02:34:30 PM »

This is just the sort of model we envisaged for the AM/MA event; something quirky and flyable. It looks so much better than the original with the reduced dihedral
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Squirrelnet
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« Reply #43 on: November 25, 2018, 02:52:24 PM »

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reduced dihedral

Funnily enough this is what is shown on D Hayward's plan - 1" at the tip . But the model in photos from the 1970's looks more like my Tomboy, that looks more like 2" to 3" at the tip to me. I'll stick with my scale-ish setting, looks enough to me

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Squirrelnet
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« Reply #44 on: December 01, 2018, 01:21:09 PM »

Made a start on the cowling. I found a old tape roll is a useful former for forming the planking for the outer ring, when that was dry I added an inner ring which has suitably sized bottle stuffed in it to keep it round while it dries.

 I made a tailplane too. Unlike the plan, which has a lifting section tail this one is a symmetrical section. That may need a change in declage from the original D Hayward design so the plan is to rubber band it on to start with and then glue it down once the model is trimmed. I'm adding the elevator lines into the construction so it will look split but I may add a trim tab too which hopefully wouldn't loose too many marks  Undecided I was thinking of adding one to the fin too rather than hinging the entire rudder to make it a bit more reliable and easy to alter the trim for the conditions. I'm assuming that this kind of change is within the spirit of the AM/MA , the rest of the model is pretty much as per the plan

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billdennis747
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« Reply #45 on: December 01, 2018, 02:14:00 PM »

I may add a trim tab too which hopefully wouldn't loose too many marks  Undecided I was thinking of adding one to the fin too rather than hinging the entire rudder to make it a bit more reliable and easy to alter the trim for the conditions. I'm assuming that this kind of change is within the spirit of the AM/MA , the rest of the model is pretty much as per the plan
Good ideas. For the AM/MA event it would take major and widespread changes to elicit raised eyebrows. There are no static marks. It's all about getting models in the air
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Squirrelnet
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« Reply #46 on: December 01, 2018, 03:05:55 PM »

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For the AM/MA event it would take major and widespread changes to elicit raised eyebrows

Good to know - thanks Bill
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Squirrelnet
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« Reply #47 on: December 02, 2018, 01:09:46 PM »

I have added a fin to the Wilga, there's some flat 3mm carbon running up the central spar and across the top edge ( its on the other side) to add some rigidity . I've also added some panels lines so I can cover up to them and give the impression of separate elevators and rudder. Covering will be Esaki tissue over Mylar. I'll cut a trim tab into both the tail and rudder once it's all sanded to shape

Ive added a front face to the cowling but it now gives me flashbacks to a school woodwork project, hopefully this one won't end in the same way!

It's starting to look like a proper aeroplane now  Cool

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« Reply #48 on: December 02, 2018, 06:19:32 PM »

Nice work SN.

John
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« Reply #49 on: December 03, 2018, 05:18:54 PM »

Nice subject and great modelling squirrelnet.

Just wondering if or how slats work at these scale sizes?

Steve
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