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Fournier RF-4

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EarlyBird02/10/2020 20:56:11
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507 forum posts
369 photos

Glue time for the second wing yes

dscn0658.jpg

Including the top spar surprise

Tomorrow shear webs and leading edge sheeting, all being well, I hope.

The weather here in North Lincolnshire is helping with the build, cold wet and windy which is keeping me out of the garden.

Cheers beer

Steve

Fun Flyer02/10/2020 22:37:28
357 forum posts
59 photos

Looking very good EB.
When I joined the two wings together I was taken aback by the overall wingspan. I had built the fuselage
first, I always do as it encourages me to build the wings to make it fly, and it looked out of proportion to the wing.
Of course it wasn't.!!

EarlyBird03/10/2020 09:01:01
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507 forum posts
369 photos

Thanks FF.

I was going to build the fuselage first but having read Peter and your build logs I realised that to finish the fuselage fairing the wings are needed. Yes the wings do look big so I made a six foot building board to accommodate the wing joining. Now here is a test question what did I do wrong?

I am looking at the fuselage and thinking of ways to lighten the tail. What did you do and how much weight was required in the nose. I have also decided to move F1 as far forward as possible just to help with the balance.

Cheers beer

Steve

Fun Flyer03/10/2020 12:36:53
357 forum posts
59 photos

You're making great progress.
I didn't actually do anything to lighten the tail and just went with the design. Someone on here did suggest a built up tail but I thought that was too much work and could be too fragile. However it did mean that it took quite a bit of nose weight to balance the model. Currently there's 315gm fitted, most of it in the cowl.

This is how I avoided moving F1 forward.

20201003_114238.jpg

EarlyBird03/10/2020 17:12:30
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507 forum posts
369 photos

FF 315gm! you have convinced me to experiment with a built up tail and moving F1 forward.

I like you motor mount it looks easier than the ply cube that I made on my Ballerina build.

Cheers beer

Steve

EarlyBird04/10/2020 07:26:31
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507 forum posts
369 photos

A bit of progress yesterday.

Shear webs have to be individually cut and fitted due to the wing tapering. Aileron spars planed and sanded to size.

dscn0659.jpg

All dry fit as usual.

I am wondering if I am making life harder for myself by trying to be too accurate.

dscn0660.jpg

As you can see there are no gaps between the webs and the ribs. Would it cause a problem if I undersized the webs, which would be far quicker?

Time for some more gluesmiley

Cheers beer

Steve

brokenenglish04/10/2020 07:50:03
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605 forum posts
30 photos

Surely the motor mount shown above could be built up as a robust ply cube, maybe even enlarged as necessary, and used as a ballast box.

Edited By brokenenglish on 04/10/2020 07:51:25

Ron Gray04/10/2020 08:21:53
2442 forum posts
979 photos

@EB - don't be tempted to undersize the webs, they really should be a very good fit to the ribs. Danny Fenton has something on his thread about this, cut 2 pieces, butt them up to the ribs then trim in the middle to join them. Very time consuming but ensures that the strength is there by having the tight fit to the ribs.

Peter Miller04/10/2020 08:28:51
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11585 forum posts
1384 photos
10 articles

Well I hate to upset the perfectionists but mine don't always touch the ribs at either or even both ends.

The wing is still stiff enough and I can tell you that one of my models, "Dancing Girl" fitted with an OS Wankle engine and an Eagle Tree G meter tested that to the limit

I put it into a long terminal velocity vertical dive and applied full elevator. The G meter read 24.8G which meant that the wings were taking a load of 95lbs.

I think they were strong enough!!!!

Oh and due to my sequence of building I never get any warps in them

Trevor04/10/2020 08:48:18
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521 forum posts
61 photos

I'm the wrong sort of engineer to have a professional view on this but my understanding is that the webs perform two functions. Firstly, as their name implies, they impart shear strength to the spar, partly by preventing the upper or lower spar from buckling between the ribs under compression. Secondly, they improve the torsional rigidity of the wing by closing off off the leading edge D box.

It seems to me that neither of these functions would be seriously compromised by a less than perfect fit to the ribs.

Trevor

Peter Miller04/10/2020 08:55:07
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11585 forum posts
1384 photos
10 articles

Trevor, I agree although there probably is a slight loss of torsional ridgity my wings are certainly stiff enough in torsion and, as proven above, in compression

Ron Gray04/10/2020 09:49:40
2442 forum posts
979 photos

I believe that the reason we see very little difference is because, in most cases, the wings are very much over engineered, design wise. in all probability a simple piece of 1/4 x 1/4 glued vertically mid point between the spars would be sufficient!

Ron Gray04/10/2020 10:22:37
2442 forum posts
979 photos

I also don’t believe it being a perfectionist when one makes sure that pieces touch when forming a join. Let’s face it it’s a join, otherwise it would be called a gap! smile😂😂😂

Trevor04/10/2020 10:49:00
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521 forum posts
61 photos

Ah, but what do you call it when ‘it fits where it touches’? devil

Ron Gray04/10/2020 11:25:14
2442 forum posts
979 photos

I believe that is known as a joint with a bit of a gap. cheeky

EarlyBird04/10/2020 11:43:59
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507 forum posts
369 photos

Or a partial fit? laugh

Anyway you have all convinced me that I am too much of a perfectionist.

back to the build.

Shear webs are glued in, leading edge glued and sheeting pulled up and glued to the leading edge. I then used super aliphatic on the ribs.

dscn0661.jpg

Waiting for the glue to dry then shape the leading edge for the top sheet.

Cheers beer

Steve

EarlyBird04/10/2020 19:34:36
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507 forum posts
369 photos

When the glue had dried I shaped the top of the leading edge dampened the sheet and allowing it to dry.

img_20201004_191950.jpg

But I am having camera problems in that it won't work frown

and using my mobile is just plain terrible angry

That could be the end of the photos then.

Cheers beer

Steve

Peter Miller04/10/2020 20:45:18
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11585 forum posts
1384 photos
10 articles

What camera are you using??

EarlyBird04/10/2020 20:58:56
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507 forum posts
369 photos

Nikon Coolpix given to me twenty years ago and hardly used until I started the Ballerina. It just says lens error when I turn it on.

I have always found mobiles useless and only use them for text and phone calls.

Oh well I always feel a bit down when things break, Some one did suggest that maybe I have chosen the wrong hobby. laugh

EarlyBird04/10/2020 21:15:45
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507 forum posts
369 photos

img_20201004_210454214.jpg

Hmm I give up time for bed

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