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My first build, Ballerina


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On 25/09/2021 at 17:54, kc said:

That u/c block needs to be edge on  -not flat on.  Drilling the hole in situ is not advisable - better to line up the pre drilled hole in block with a bit of 8swg whilst gluing.  The hole may need slight filing to allow for the radius of the bend in the wire.  The extreme tip of the wire needs gripping to avoid slop.   And the u/c block is glued to a ply R1a half rib which is against the centre rib.

 

 

Thanks KC, can you elaborate on “edge on” please

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To me the big area of that block is the face, the smallest the ends. and the edge is the other bit!   Judging from the plan that edge is 8mm by 28mm.   So the wire u/c goes as far as possible into the block without coming out through top of the wing.   The extreme end of the wire is the bit that needs holding and I guess the block is about 23 to 25mm in that direction and the wire penetrates all that 23mm.   It's a leverage thing - the further up that wire goes the easier it is to hold still.  The hole in the block should be just same diameter as the wire.  Slop in the fit will be magnified 4 or 5 times at the wheels.

No doubt the engineers will have better terms to describe than I have used.  But I think you get what I mean.

I also advise that where the wire goes through the ply and into the block that the hole is eased ( rounded/radiused) with a file or knife because there is always a radius to the bend in thick wire.  So easing allows the wire right into the groove and the saddle clamps sit flat.  So much easier to do all this at an early stage.

Tricky to drill holes in tiny blocks so hold in a vice or Workmate to prevent splitting.   Frankly the blocks could be a little bit thicker if you have to make new ones. Bits of beech from old chair legs is a good source of material. Or one could laminate from layers of 4mm ply and leave a gap to create hole.

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This wing mounted u/c looks nice but I prefer a fuselage mounted u/c because the wing is easier to store and transport.   If you have any problems consider fitting blocks for fus mounted u/c as well.  See Peter's other recent designs for how this is done.

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I drilled a pilot hole through the block. Lined the hole up with the centre of the groove. When the LE bottom sheet is pulled up I drilled the pilot hole through the ply and bottom sheet. This gave me the location of the groove, very handy for later.

Details start here and continue on subsequent posts.

As always I hope this helps.?

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So build has been slow this week, I hope to get back in the workshop over the weekend. I'm annoyed that I didn't understand the plan better with regards to the undercarriage. Now the sheeting is on the bottom I do not have enough support for the undercarriage wire. I suppose I could cut into the sheeting and glue two small strips of ply to create a channel, what do you think?

Incidentally the other wing is yet to be built so I would have to treat both wing the same I guess. I would rather not go down the route of fitting a fus mounted undercart as I think this will spoil the look of her. Grrrrrrrr.

 

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Edited by Steve Goodwin
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saddle clamps would be OK - one at each end and located quite near the ends.   2 each side, total 4 required.  Maybe an extra one near the wheel end making 6 required.  Need to be the correct size for the wire and single types not double. Not the flat type either, needs to be grooved for 1 wire.     Note saddle clamps are not rectangular so use them to mark the cut out in the sheeting, obviously they go in a hole in the sheeting.  Ensure the screws bite firmly in the ply there is a lot of stress on the u/c.   In reality it's best to let the screws pull out in a hard landing rather than damage the wing.    So screws are used not bolts and nuts. 

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  • 2 weeks later...

Well having examined the RCME plan and Peter's original hand drawn plan plus looking at my own model ( as yet still uncovered so i can see my construction ) I can see that just extending the 1/16th sheeting a little over the ribs produces  a TE that is satisfactory without adding the 1/8 TE strip specified.   I found it easier to ensure the top and bottom 1/16th sheeting is a full 7/8 ths inch and this makes the wing exactly the right size.   Gives some scope for sanding the edge to at taper.   I thought it would be stronger than glueing a strip edge on to the 1/16th parts.

Basically make the model whichever way suits you!   I found making the sheeting 7/8 wide ( instead of 1/2ins) worked well.

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