Flamingo 3.5metre by Chris Williams - scratch build

[Ron Gray]

That's a real shame about the damage Peter but thanks for the detailed photos to show where to add some strength, I'll certainly take that on board when I build mine.

[Murat Kece 1]

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Peter You need to add at least a couple of these to keep the good fortune. I can post you a small one... I find that it at least helps the mind.  

[Peter Garsden]

4 hours ago, Murat Kece 1 said:

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Peter You need to add at least a couple of these to keep the good fortune. I can post you a small one... I find that it at least helps the mind.  

Sound idea Murat. Anything helps. I find that if an accident is pilot error and you were a clot one is resigned to fate but when it was silly and easily avoidable as here it is very annoying?

[Ron Gray]

17 hours ago, Peter Garsden said:

Good idea Ron. There is a picture of a chap who did just that in one of Simon Cocker's columns recently. 

Where was that Peter, would be good to see what motor he used. At the weight yours came in at a Hacker A30-12 with 6.7:1 gearbox might be suitable.

Edited March 23, 2021 by Ron Gray

[Peter Garsden]

It was the last article that Simon Cocker wrote in RCM&E a couple of months back. It was a yellow version. 

[Ron Gray]

Ah the FES article!

[Peter Garsden]

 

This is the strengthening I have done - all cloth wetted out on polythene, 1 layer 170 gram Kevlar - sharpened the scissors first, 1 layer 150 gram Fibreglass and a final layer of 80 gram Kevlar. Conrad I think I got this from MB Fibreglass but I am not sure. I made a paper template to get the shape first.

[Peter Garsden]

Another issue I had noticed was that the tailplane was coming loose at the front. It is fixed with a plastic bolt (very handy sanding cylinder glued to the top to help you turn it) in the middle which was firm but a 2mm carbon pin at the front. I surmised that the hole had worked loose, but when I disassembled it and looked, the pin it had worked itself loose in the balsa. It could be that the grade I chose was too soft, but in any event I decided to mount it in a small piece of dowel, and mount a 2mm id carbon tube left over from an elevator control rod in the tailplane mount. Any new builders might  like to do the same.

 

 

 

 

This shows the tube before it was glued and pushed into the hole of course. I quickly assemble the tailplane to make sure it was in the right place then removed it again to stop the glue jamming it.

 

[Ron Gray]

Another good tip which will come in handy - thanks Peter.

[2W]

My Flamingo is progressing slowly, but a couple of points which might help other builders:

 

1. When the length of each former is measured with a flexible ruler, it is clear that it is necessary to taper each plank from F4 back to F5 and also forward to F1, with the taper being most pronounced between F2 and F1. At first I started shaping the planks by sanding the edges to avoid gaps between them, which was time consuming and boring due to the slow progress. Being a lazy blighter, I tried soaking the 9mm ply strips overnight with a damp or wet towel. This not only makes the planks much more pliable and easier to fit, but also makes it possible to shape them much more quickly with a razor plane to get them to fit exactly to the shape of the adjacent plank. It also makes it possible to pin them to the formers with large T pins using a small hammer.

 

2. The tailplane gave me some trouble. I weighed down the bottom sheet with my usual lead weights along the back edge and also the front edge with tailplane on the jigs and left it overnight. In the morning I found it looking a little odd: it was a flat 'W' shape!

I started again by salvaging the formers and laid them out. I measured the height of each former at the front and rear and planed a taper on the bottom of the the 6mm rear beam from T2 to T8 and for the false leading edge. Having stuck the formers to the rear 6mm upside down beam and then added the top sheet by glueing it to the rear beam and glued each former from their mid points back to the to the rear. When the glue had dried, I then glued the sheet to the formers and the false leading edge.

I cut the bottom sheet in two, and repeated the glueing as above, clamping first at the back and then when the glue had dried, glueing and clamping it to the false leading edge.

When both sides were done, the tailplane was perfectly straight without the previous distortion.

 

Hope this helps,

William

[Peter Garsden]

Good points William

1. Chris Williams makes it clear that it doesn't really matter if the ply 1.5mm planking is not accurate because it will be covered with P38 filler which will fill in any gaps. If you are a perfectionist then certainly it is possible to go through the process you describe, but I am a bit of a lazy bodger so didn't bother with small gaps. The planks would be very difficult to trim to exactly the right size for the reason you clearly state. Also the inside is lined with fibreglass cloth to again fill in any gaps. With hindsight, I would recommend 3 layers of cloth because, particularly at the nose it is quite delicate. I would wrap over the cloth into F1. If you read earlier in this blog you will see this in more detail. So BODGE IT I say.
2. I had the identical experience with my tailplane. In fact I got confused as to which way up it was, to such an extent that I am not convinced that it is now the right way up. So mark it appropriately. I used some amonia, I think to get the tailplane sheets straight again.  The watch word for other builders is don't use too much weight, or use lots of pins instead or some bags full of water?

[Peter Garsden]

D

Edited June 16, 2022 by Peter Garsden

[Peter Garsden]

My mate Keith just recorded a further flight of this amazing glider at Back of Roaches, Leek Staffordshire on September 29th in a 15mph wind. Really moves when you give it some encouragement. Also turns on a sixpence, if you remember them. If you don't then 5p.