Percival Vega Gull

[Outrunner]

Looks fantastic John! I'm following in awe.

 

I really like those old airplanes with folding wings.

[John Rickett 102]

The left wing was progressed sufficiently to allow sorting out the hinges and making sure the dihedral was the same as the right wing.

 

 

I was quite pleased with the result so thought I’d drop the fuselage over the centre section to see what it all looked like. At this point I realised I’d made a catastrophic error, the geometry of the wing fold is completely wrong meaning that when the wings retract, they follow a descending arc and end up below the level of the tail wheel by a considerable margin!

 

 

The reason is that the dihedral was incorporated into the centre section ribs not the outer panels, I did this to maximise the available thickness of the wing which occurs in the centre section and reduces progressively toward the tips. I didn’t think at the time that having the hinge axis at the dihedral angle would have any effect on the wing fold, but of course it means that the retraction plane is angled……..in the wrong direction.

 

Having played with making up some more hinges to move the hinge axis in the opposite direction, which works to some extent, I’ve concluded that the gap between the centre section and the wing would be too great.

 

 

It would be major surgery to cut out the hinge supports, straighten up the centre section outer ribs and start again, as well as adding weight, so I’ll just have to live with the situation.

 

 

Here the wing is now higher than the tail wheel but there would be a large gap to fill between the centre section and wing which would also put the trailing edge out of alignment.

 

Its not the end of the project, the wings will still fold for transport if a tail support is made to keep the tail off the ground sufficiently, but with the wings stowed it looks a bit silly and defeats the original intent of a practical model with folding wings. 

 

This model may now be put on the back burner until enthusiasm is rekindled.               

[Ace]

I am gutted for you John as I have been following your progress with great interest.  Hopefully a solution will emerge once your disappointment has subsided.

[Richard Crapp]

I don't think that is a big problem . You just have to alter the vertical plane of the hinge.

Like re-fix it with the bottom of the hinge more to the rear. You might have to insert some more hard wood.

The real one had warnings about not stressing the hinge area , the tips to be supported during the fold process.
  In the  pictures you can see the tips nearly hit the flore when folded.

[RottenRow]

Don't give up John!

 

Could you make new bottom hinges, with the pivot point offset? Something like this drawing.

 

 

The modified hinges would mount in the same holes on the spar. The actual amout of offset required would probably be quite small.

 

The wingtips would then move on an upward arc as the wings are folded (viewed from the rear).

 

Brian.

[Basil]

16 hours ago, Ace said:

I am gutted for you John as I have been following your progress with great interest.  Hopefully a solution will emerge once your disappointment has subsided.

Ditto.

Bas

[alan p]

If the hinges are set vertical  in the ribs when folding the wing it will adopt the incidence angle of the wing, as the others have said pitch the hinge equivalent to the incidence or slightly greater to the vertical and it should fold parallel to fuz centre line. Excellent build so far shame to halt now👍

[John Rickett 102]

Thanks for the commiserations and good suggestions, repositioning the lower hinge pivot more to the rear would probably be the least amount of work. I think I could experiment with the left wing as little has been fixed which cannot be easily cut away. It would need some 2mm flat bar about 25mm wide, if anyone knows of a source?

 

 

 

If it works for the left side I'd be a bit more confident about cutting into the right.

 

 

The folding flap section may have to be relieved at the top and bottom to make space for a repositioned hinge but it’s hardly a stressed area, spruce was used only to allow the hinges to have a decent anchor, so would be simple to modify.

 

 

The top hinge would need remaking and angled back to allow the M3 bolt to line up on all the holes. The hinges are only 2mm mild steel so will withstand a small amount of twist which will be easier than making the wood supports with an angle which accommodates both the dihedral and the offset we are now talking about.

 

 

The first idea was to move the top hinge forward, but moving the lower one back is a better suggestion.

 

 

This is the view from the underside of the centre section, right hand side.

 

I really don't want to straighten the centre section ribs as I'm sure it would end up weaker. The undercarriage mounts are right at the edge and the holes were awkward to get right, plus the leading edge is now in the way.

   

After the last few days of deliberation, I’m now a little less circumspect and hope that the original plan of practical folding wings can be achieved. The model was always going to be sport scale, my building skills aren’t to competition standard, so these modifications won’t potentially lose any scale points.

 

Schoolboy trigonometry will have to be brushed up to calculate the amount of offset which will put the wing tip just under the tailplane. As there is the existing dihedral which was the original culprit, I don't think its a simple calculation, but a bit of experimentation without spoiling what is already there will probably yeild a result.

 

Interestingly, the picture below shows the Proctor wing fold attachments (this one awaiting restoration at East Kirkby) and there doesn’t appear to be an offset in the rear mounts, perhaps there doesn’t need to be if the end rib is perpendicular – my fundamental mistake I think.

 

 

The Proctor was the military successor of the Vega Gull and apparently retained the same wing fold.     

[Nick Cripps]

As a first approximation, measure the distance you need to raise the wingtip to match the desired height relative to the tailplane. Divide that measurement by the distance from the wingtip to the hingeline and then multiply the result by the vertical distance between the top and bottom hinges. This will give the rearward offset required for the bottom hinge (with the top hinge remaining in the same place, albeit twisted to match the new hinge axis).

 

I don't think the dihedral will make any difference to this calculation so the principle of "similar triangles" should work.

[RottenRow]

2 hours ago, John Rickett 102 said:

It would need some 2mm flat bar about 25mm wide, if anyone knows of a source?

 

You can buy this from B&Q. 25mm x 2mm x 1 metre length.

 

https://www.diy.com/departments/black-varnished-drawn-steel-flat-bar-l-1000mm-w-25mm-t-2mm/254141_BQ.prd

 

Wickes also sell some sizes, but only upto 20mm wide in 2mm.

 

Brian.

[Richard Crapp]

Any build news John.? I look forward to them. I am just getting a bit more done on mine.

[John Rickett 102]

Richard, pleased to hear you are making progress.

I played around with some offset hinges and did get the wing to fold just below the tailplane but the wing join wasn't pretty. As the model wouldn't be ready for this year, setbacks or not, I decided to concentrate on two other models in need of some repair and restoration which could be brought up to the painting stage by the time the weather improves. These are on track so hopefully I'll be back on the Vega Gull in the spring although I don't tend to get a lot done in the workshop during the warmer months.

I'm resigned to having the Gull's wings fold well below the intended position, which won't affect the looks, once assembled, or the flying but of course will look very silly sat in the van.

Us modellers have to be made of stern stuff!            

[Richard Crapp]

It's about the same with me. I had to put the gull aside to freshen up the 12 year old Wessex try-motor that may be called for flying duties.

It's done except for test flights so I can now tinker with the Gull but wont get it flown this year.

 

I was going to ask if you knew how many hinges the rudder had? but i decided on 3 and its done now.

 

Don't get to hung up by folding wings. I found out with the Swordfish they can be more trouble than their worth.

Mine fold but only after I remove the wing tube!

More of a party piece than useful.

[John Rickett 102]

While having to wait for decent painting weather for two other projects, I thought it therapeutic to progress the cabin interior.

 

With Beryl looking a bit more life-like with some colour in her cheeks and with a new completed control column to grasp and straps to keep her in position, it was time to prove that she and the tanks could all be fitted through the doorway.      

 

 

 

Major surgery was required on her feet (her ankles had to be removed) to clear the obstruction of the radio tray, even so as the butchery is low down below the instrument panel, I don't think it will be very visible. Beryl didn't say a word.

 

I doubt a four-point harness would have been fitted originally but to my mind its in keeping with a perilous record attempt and its all that holds her in the seat.   

[Richard Crapp]

Nice advantage of those huge tanks is that it will save you from detailing the cockpit.

I did not want to see here toes anyway!

[John Rickett 102]

Satisfied that the cabin interior parts would go through a doorway with sufficient margin, attention was paid to making the doors.

With multiple curves, the challenge was how to make them to hold the correct shape, yet be light and strong. I first considered making a mould and laying them up in fibreglass, removing all but the frame afterwards. I’m sure this could have worked but I wanted a way of building in a rebate for the glazing. There may be other suitable methods but I settled on making them out of laminates of ply having first proven that the ply would bend sufficiently and then hold its shape and that the corners could be made strong. The frames couldn’t be more than ¼” wide otherwise the result would look clumsy.

 

A couple of test pieces were made up as in the pictures

 

0.9mm ply once wetted and allowed to soak for 10 minutes then laid up in 3 strips over a suitable former, will hold its shape.

 

 

By overlapping alternate corners, the strength is as high as it needs to be. No attempt has been made to force the joint to destruction, but in pulling at it as if it were a wishbone, satisfied me that this type of joint is more than adequate.    

 

 

 

The doorway former was made form scrap bits, covered in parcel tape or Sellotape and clamped into position. Each side has a curve to some degree. 

 

    

 

It was then a case of adding the ply strips and slowly building up the layers.

 

 

There are 6 pieces to each layer with 6 layers required to get to the desired thickness. With each strip being wetted the drying time takes longer so is quite a slow process...but we're getting there.

 

  

[Richard Crapp]

Strangely I was working on the Gull 4 dores yesterday. They are a different style to your Vega Gull. Part of the Gull evolution.

The top at the moment comes off and can be hinged to the rite. To make the dore on the left open will require some sawing!

https://www.rcscalebuilder.com/forum/forum_posts.asp?TID=35651&PN=1&TPN=15

 

There are three nice photos here  including the cabin

file:///C:/Users/Richard%20Crapp/Desktop/PERCIVAL%20GULL%20IV%20-%20Classic%20Aircraft%20Sales%20Ltd.htm