Dihedral wing half joiners ?

[John Wagg]

Looking to build a vintage plane which has a dihedral wing. 

What I want to do is have it split in the middle for ease of transport but secure enough for flight.

My last project had a wide flat centre section so was easy to do with tubes & rods.

This model though has virtually no flat middle section so is a bit more complex.

My own thought is a rectangular ply box in each wing with a ply spar joiner.

Two 'spars' needed, one for strength and another for wing alignment.

I would expect the main spar to have to go into the wings a little bit so as to spread the load and stop the wing folding.

Maybe not, as the wing will be either rubber banded or using wing bolts.??

Another thought would be piano wire in tubes but not sure I could get a sharp neat 'V' in the middle.

I want the split to be in the middle. Not a separate centre box with each wing plugged in.

Any suggestions please or ideas for a neat strong system ?

 

For reference the model is a TD Coupe, 64" span and has a 4 inch dihedral under each tip. Ribs are 1.1/4" deep :-

https://outerzone.co.uk/plan_details.asp?ID=5367

 

Thanks'

John

 

 

[Ron Gray]

Both my Rascal 110” and Leprechaun XL have dihedral with split wing sections. They have. Joiner boxes in each wing section and an aluminium joiner in the case of the Rascal and ply in the Leprechaun. Both use pins to line up the wings, no secondary spar joiners.

[Frank Skilbeck]

My 88" span Majestic Major which looks like it has a fairly similar center section is joined together with 3 sets on straight piano wire, 2 on the main spar above each other and 1 towards the trailing edge. Model is 30 or so years old and I don't have the plan anymore. About 5 years ago I did replace the piano wires as the originals had taken on a slight bend increasing the dihedral. 

 

On our larger scale vintage gliders we use the brass box section with steel joiner, like these with a pin towards the trailing edge to ensure alignment. 

[John Wagg]

1 hour ago, Frank Skilbeck said:

My 88" span Majestic Major which looks like it has a fairly similar center section is joined together with 3 sets on straight piano wire, 2 on the main spar above each other and 1 towards the trailing edge. Model is 30 or so years old and I don't have the plan anymore. About 5 years ago I did replace the piano wires as the originals had taken on a slight bend increasing the dihedral. 

 

On our larger scale vintage gliders we use the brass box section with steel joiner, like these with a pin towards the trailing edge to ensure alignment. 

Thanks for replies Guys.

Frank, what do you use for tubing with the piano wire ?

 

[Engine Doctor]

My Frog 45 is designed with a hard wood dowel for spar/ plug together wings. I chose to use 1/4 inch carbon rod  slide fit into  brass tubing for dihedral brace. The 45 has on occasions been flown in a very un vintage manner and stood up very well. Now over 10 years old and going strong.

[Ron Gray]

Some shots of the Leprechaun XL

 

Wing boxes being assembled

 

Shot showing one in the wing

 

 

Ply joiner / brace in the fuse

 

[Gary Binnie]

You can use a straight joiner if the slots for its tubes are cut at the dihedral angle in a hardwood spar filler.

The first photo is of my Chris Foss 144" span Multi-Phase, the wood is Ramin from a local picture framing shop.

The wood is laminated with thin ply, the longer ply part keys in to a vertical slot in the foam wing and glues to its single 1/4" spruce spar.

The tube is epoxied in, I seal the open outboard ends with masking tape to stop it seeping in.

It's glued in in one piece then cut in half after it's set for accuracy, there is an allowance for a ply root rib to be added, the tube is then filed flush.

 

For a built up wing the wood block can be fitted between the upper and lower spars then closed with ply (Chris Foss Hi-Phase)

 

I used quite large diameter steel rod for the Multi-Phase but for your model a 6 SWG wire joiner and aluminium tube would probably be ok. I have a chart somewhere of the number and size of joiners needed for gliders based on their wing span.

 

Chris's 100" Centi-Phase uses a vertically stacked 6 SWG joiner system the same as this, the second joiner can be left out for gentle flying or not built in at all (i.e. not bungee launching in windy weather).  

Both designs use a thin incidence peg with aluminium tubes (14 SWG) to keep the root ribs aligned, I flew the Centi-Phase without it once and had a fun time trying to trim out strange roll behaviour!!

 

I use carbon joiners in my competition gliders where they were manufactured with them but prefer piano wire for sport gliders as it only bends on a windy bungee launch, I've snapped carbon joiners before, they let go without warning. 

 

1. Multi-Phase joiner system.

 

 

2. Centi-Phase system, upper wire is 6 SWG, lower is 8 SWG (and shorter than the main joiner). The incidence pin can be seen behind them.

 

 

3. Centi-Phase root rib.

 

 

4.  The Hi-Phase uses three 6 SWG joiners, in this photo I have the wing vertical so that epoxy fills the space around the tubes by gravity. I have just added the ply webs fore and aft on the centre joiner. Instead of one piece of wood for the joiner it is short sections filling in between the ribs, hard balsa instead of hardwood. Extra tube is overhanging for the ply root rib to be added later. 

 

Edited April 5, 2023 by Gary Binnie

[Gary Binnie]

Adding some more photos of the Hi-Phase, in the previous one the upper spar is not fitted and I'm gluing in a balsa web, not ply.

 

Panel on the right has no upper spar. The spruce spars are widened at the root for the increased stress, outer tip panels use balsa spars for weight saving. The built-up version of the Centi-Phase has spruce/balsa spliced main spars. 

 

 

Dry fitting ply webs loose in their rib bays before adding epoxy and closing up.

 

Edited April 5, 2023 by Gary Binnie

[Frank Skilbeck]

3 hours ago, John Wagg said:

Thanks for replies Guys.

Frank, what do you use for tubing with the piano wire ?

 

John, brass tubes as shown by Gary, when I say piano wire I'm referring to the 5 - 6mm dia stuff

[Mike T]

Blade & box work fine. 

I like the idea of 'stacked' tubes though - never seen that before!  I'll give that a go when the opportunity arises.

[Andy Stephenson]

I made a dihedral brace out of bent piano wire for an 8ft glider each about a foot long. One 8 gauge at the spar and 2 x 10 gauge fore and aft in the wing section fitted into brass tube. This proved more than adequate for anything I threw at it.

[John Wagg]

Thankyou all for the replies.

From the options above I'm probably going down the piano wire route as it's simpler to construct round holes for tubes etc.

Just need to sort a design and details.

 

Regards

John.