Jump to content

Fournier RF-4


Recommended Posts

Thanks FF,

I have just lifted it from the board to work on the leading edge my initial thoughts are how light it is and that the wash out wedges have done their job. surprise

Looks like good flying weather today but my main reason for going is to swap onions for apples, does that make it a swap meet? We had a swap meet planned for October but it has been cancelled now sad as we are all keeping each other safe.

Cheers beer

Steve

Link to comment
Share on other sites

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.!!

Link to comment
Share on other sites

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

Link to comment
Share on other sites

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

Link to comment
Share on other sites

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

Link to comment
Share on other sites

@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.

Link to comment
Share on other sites

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

Link to comment
Share on other sites

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

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...