Rogallo Sail?

22 March 2024

Rogallo Wing Advantages:

• Simplicity: Easy to build and lightweight, perfect for low wing loading models.
• Inherent Stability: The curved profile creates lift and some inherent pitch stability without separate horizontal stabilizers (in low wind conditions).
• Low Stall Speed: Works well with low wing loading models that need low airspeed to stay aloft.

Rogallo Wing Disadvantages (Reduced Washout):

• Decreased Stability: Reducing washout (wing twist) improves lift but decreases inherent pitch and directional stability.

Adding Stabilizers:

• Improves Control: Vertical and horizontal stabilizers (fin and rudder) compensate for the reduced stability from washout reduction.
• Enhanced Maneuverability: Allows for better control over the model's pitch and yaw (turning).

Considerations:

• Size and Weight: Keep stabilizers lightweight to maintain the low wing loading advantage.
• Balance: Carefully balance the model with the added stabilizers to ensure proper flight characteristics.
• Wind Conditions: In higher winds, additional stabilizers become even more important for maintaining control.

Overall, using a Rogallo wing with added stabilizers for a low wing loading model is a viable option. It offers a good balance between simplicity, lift, and control.

Here are some additional points to consider:

• Experiment with Washout: You can experiment with different levels of washout to find the optimal balance between lift and stability for your specific model.
• Control System Design: The control system for the rudder and elevator needs to be lightweight and efficient to minimize drag.
• Flying Practice: Models with Rogallo wings and additional stabilizers can still be tricky to fly at first. Be prepared to practice and adjust the control throws for smooth flight.

You could probably do up a model this way but it would need much convincing if I were to do a scale subject. For one, if CF rods were used as the leading edge (and only spar) of the rogallo wing, for lightness, it would bend under the strain of the sail and the trailing edge of the sail would also be ballooning. It wouldn't look right.  

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Rogallo rc, need find geared motor, WLToys, other mini receiver

FF with stick or foam, solder capacitor

Sniffi glider, 2mm depron glider

Late 280: seaplane, plank/delta

Twin motors: from KF606, E010, E009; for parachute, twin planes, biplane, extended wing

1/2 gram receiver: solder thin lacquered wires?

Rogallo using drinking straws for spars?

Obviously only suited to AUW of only about 10g?

And is it acceptable to have less sweepback? I think so, let's say we only want sweepback of 20degrees. 180degrees -2 times 20degrees is 140 degrees. Give maybe 10% for the rogallo sail, so that makes it 150 degrees for the sail foil. Maybe it is better to cut out some at the keel and leave some at the tips.

Over A3 sheet of paper, draw the sail's dimensions. Draw parallel lines so that keel and spars can be wrapped by sail.

Flatten a piece of drinking straw, make a strip of cardboard which has the width slightly wider than the flattened width of drinking straw. The centre keel may alternately be inserted through alternating slits in the sail. To make the pockets for the spars, place the cardboard strip along a leading edge and then fold the outside and stick the sail foil together with double sided tape. Withdraw the cardboard strip and a pocket is formed neatly.

Paper Rogallo?

Again, targeted for AUW of only about 10g.

A4 paper can make a mini rogallo sail. The leading edge will not exceeding the breadth of the paper. The maximum wingspan is around the length of the paper and area around 3/4 of the paper's area. A paper airplane's or dart's wing's strength relies on single folded paper. Maybe a paper rogallo of single layer but with strengthening on lines and edges by folding once and with the curving foil is strong and rigid enough.

 Cut a square from A4 with a diagonal crease. The leading edges have 5mm overlap glued. Mark centre of leading edge for strut support. Extend a line between the 2 strut support locations. Where the line intersects with the keel (that's the diagonal crease mark in the beginning), is the central column support location, 5mm either side are the central strut support location and this gives additional dihedral to the rogallo.

Pierce the 4 holes, insert a thin bamboo stick and bring in the leading edges slightly so that the paper is curled. The rogallo is now basically done except for CG adjustment and the addition of central strut structure for the RC stuff.

A 3 ply foam gondola can be constructed to house the RC gear and the 1s cell. The center laminate is cut from 5mm foam to hold the RC gear and 1s cell. The outer laminates closes the RC gear and 1s cell and can be thinner foam.

2 pieces of 2mm foam strips can be the hanging central struts, placed at a Vee to each side of the gondola. At the top of each end is a hole where the thin bamboo stick passes through. The 2 motors are glued to the struts. At this point, the whole gondola and V struts will pivot around the thin bamboo stick. A 3rd strut is needed to set the gondola at the correct angle to the keel of the rogallo.

If the paper rogallo crumples too easily at the nose, additional thin bamboo stick can be inserted in the keel.

I experimented with making a simplified rogallo from an A4 sheet of paper:

• too flimsy with paper alone, the folded leading edges are too weak to maintain form.
• it is easier to fold than to curl, When I thought about it, two cones can be represented by 2 folded cones, isn't that the Dart280 idea?

So the conclusion is, without the supporting frame, paper itself is too flimsy, CG was definitely wrong and the flying speed required for a glide was apparently fast which isn't what I'm after. If supporting frame is required, then might as well use lighter sail material?