Heinkel P.1076 - Ribs wing build log

[chiloschista]

Hello,

I start here a build log of the ribbed wing version of that PSS plane.

I would like to keep it clean and stick to the topic. For general questions I would prefer using the main thread here.

In the case someone will build one too, it would be of course nice to share experiences here.

I will try to answer questions related to that build and welcome other suggestions too.

Ric

 

[chiloschista]

Materials list:

Balsa 1.5mm, 1000mm x 100mm, 6x (wing sheeting)

Pine wood 3mm x 5mm x 580m, 4x (main spar)

Balsa 2mm or 3mm for main spar (doesn't change a lot, balsa from scrap box is excellent)

Ribs set of 3mm plywood (4x) and 3mm balsa (16x), (CNC cut)

Various parts of 3mm plywood (CNC cut), 6x

Balsa 10mm, 15mm x 580, 2x (leading edge)

Balsa

Hard wood dowels, 6mm Ø x 100mm, 2x (alternatively, through the fuselage and rubber bands)

Plywood 2mm, 67mm x 50mm, servo tray base (CNC cut), 2x

Servo trays, printed in ASA, 2x

Wing tips, printed in foaming ASA

 

 

[chiloschista]

First step is gluing 3x 1.5mm balsa sheets, with thin cyano glue. That will get sheet coverings for one wing. 

Please remember: 

- Protect the build base with transparent film, as thin cyano goes through balsa sheets 

- Two wings are needed

- Preferably a left one and a right one

Yes, I know a couple of builders who did build two left wings and no, I'm not one of those

[chiloschista]

Measure following drawings and trace on the sheet. Increase chord by 1mm to compensate for camber.

Measure again and cut. 

Put the piece on the rest of the sheet and cut a second one. 

Repeat for the other wing.

Please remember: 

- Measure twice, cut once!

 

[chiloschista]

Clean ribs and check the fit with pine spar and other pieces. They need some little rework as the general alignment is not normal.

Put a transparent film over the sheet and place ribs. Don't glue it now! 

I did use the plywood vertical spar reinforcement and a Duplo block as reference for distance and square. The last rib distance will be shorter.

The first two plywood ribs are 3mm offset backwards, because there will be a 3mm plywood piece in front of them.

Important! Use the servo base to check that distance (should be the same).

Glue all ribs with thin cyano.

Please note that dowel holes are offset, to match leading edge.

Please remember: 

- wings are swept forward! 

- one left and one right panel are needed

- check twice, glue once

 

Place some scrap balsa under the plywood sheet, to avoid compression when fixing wing to fuselage. Trim it to ribs level.

 

 

Go through the fixing screw hole again, otherwise it will disappear when covering the bottom side.

 

[chiloschista]

At this point the top sheet will be glued with thin cyano to the structure, taking care of the alignment: the front of the ribs aligned with the front line of the sheet. A few tenths of mm are left inwards, so after sanding the leading edge is nice straight and square.

(See picture in the next post.)

 

[chiloschista]

Now the main spar will be reinforced with 2-3mm balsa sheets (whatever is in the scrap box) between the ribs in front of the pine rods, with vertical grain.

This will avoid compression between the sheets and gives a lot of longitudinal rigidity to the wings.

Care will be taken to work on a flat surface, as this stage will give the straightness of the spar and the wing itself.

[chiloschista]

It's time to place the servo trays, which are printed in ASA. Those are for planned KST X01 mini, but fits the 135 too. There is a left and a right one.

 

They are placed towards the inner side, taking care of the rod exit side. To fix them medium cyano and activator does the gluing job very well.

Probably I won't use the upper part of the trays.

A hole has to be cut to let servo wire come out. 

A line is traced parallel to ribs and reported to the outside of the sheet, to have the exact rod exit point.

Then the exact position of the servo trays is traced outside the bottom sheet, to find it easily when the wing is closed. 

 

Servo wire is placed for future use.

Please remember: 

- servo trays are left and right and should go in the right place

- sign the bottom sheets as left and right, otherwise the drawing get lost inside 

- fix the wires! Inserting them in a closed wing could be time consuming

[chiloschista]

Let proceed with the bottom sheet.

This step requires care, because it will set the washout of the wing, which should be at zero degrees. 

It will set torsional rigidity too, which makes washout difficult to correct afterwards (but still possible).

I did use white glue, so if the washout is slightly off it can be corrected heating the wing with a heat gun, after the glue has set. The glue will soften with heat and allows some bending. 

The trailing edge is kept in shape with two aluminium profiles, to have it nice straight.

A 10mm piece of balsa is used at tip side to have the correct washout, with the 20mm profiles keeping the trailing edge aligned on the workbench.

After the glue has set, the trailing edge is reduced to about 1.5-2mm, sanding the upper sheet. Otherwise the trailing edge is 3mm thick and this give the extrados a nicer shape, closer to original airfoil.

[chiloschista]

After the glue has set, the sheets are trimmed to planform.

A 10mm X 15mm balsa sheet is glued with thin cyano in front of the ribs.

It will be slowly sanded to shape. Yes, at beginning I use a rasp

Seems straight.

Please remember: 

- a leading edge small radius is better for hard aerobatics, but more prone to stall, especially at tip

- a bigger radius is better for relaxing flight, which for such a plane I guess should be a first choice (less prone to tip stall)

P.s.: at this point, the proud builder, beside checking how the complete plane looks like, does some wing lift test... Don't lie, you know what I mean.

[chiloschista]

Servo trays location was found again.

[chiloschista]

Wing tips were printed in low viscosity, foaming ASA and ultralight polypropylene. Both materials are very light and held temperatures up to around 100°C. PLA start to soften at 50-60°C already.

Both materials tends to warp during printing, despite heated bed and adhesion glue, but that can be fixed. 

Alternatively it could be done with balsa, but the advantage of having them exactly the same is lost. 

Or simply print them in PLA or LWPLA.

[Andy_B]

Love this Rich 

[chiloschista]

On 15/05/2024 at 22:50, Andy_B said:

Love this Rich 

Thanks Andy, you can't imagine how much I'm enjoying that simple, small build. Probably related to childhood...

[chiloschista]

A day was devoted to ailerons.

First, the drawings are reported on the wings.

Check with a lamp the position of the third rib: cut outside it! It could be slightly off.

Some lines are traced then to fit the 5mm balsa sheetings. 

The extrados looks like this. 

The intrados is a bit more tricky. 

On the wing side the cut remains vertical, 5mm then. 

On the aileron side it has to accept the aileron throw of 20° as well as the sheeting, so 5 + 5mm at root (total of 15mm) and 5 + 3mm at tip (total of 13mm). This is important to avoid unwanted torsions on the aileron.

Intrados, root side:

Intrados, tip side: 

I mistakenly did not consider the increased thickness of the angled outer sheeting and had to rework it, removing approximately 2mm. This could be avoided adding ~2mm to the cuttings on top and bottom side. Which side is the same, maybe better on the wing. Otherwise the trailing edge of the aileron will protrude 2mm.

[chiloschista]

It's cutting time. 

Ailerons first! Because it's easier to do the second cut on the wing rather on the aileron.

Flexible rulers are better suited for this task.

Start cutting just the sheets, top and bottom and then cutting the ribs from top. Looking at the picture should be clear the reason

Sheetings are glued with thin cyano and trimmed to shape.

The aileron has to be closed at root side. We don't want a plane that will whistle at each turn, do we?

And of course, before going bed...

 

[chiloschista]

... a last look  

[oipigface]

2 hours ago, chiloschista said:

before going bed..

Good night, Ric. Sleep tight.

[chiloschista]

Servo arm is shortened to first hole. There are several included, so the choice goes to the one with the closest holes to the pinion.

Everything fits inside the wing. A cover with a small hump will be printed in ASA. 

The horns will be glued in a hard balsa insertion. There linkage will be covered with a 3D printed cover. Everything that helps limiting parasite drag is welcome. 

Time to join the wing panels is approaching.

[chiloschista]

I got stuck several days with that piece. I went through several alternatives, between wood structure, 3D prints or fibreglass forming. Finally found an acceptable 3D printed solution.

It matches surprisingly well the fuselage and the airfoil. 

As this should not be a landing impact zone I guess it will survive slope usual landings.

By the way, it is quiet strong, when glued in place.