The ALBATROSSby Maxime ROUSSELLE
Since 2 years, I was flying a blue bird, 3 m span and large wing ratio of 7, but I never wanted to publish plans because it was (and is) too difficult to set-up : each time you mount it, you have to find symmetry again, by moving several set-ups... which interact. I want not to speak of water that unstresses the canvas, and you have to do it again. And if it goes right in low winds, it can with same set-up go left in strong ones and even circle, because the shape changes.
BUT ! But I can make it fly steadily for some hours. And I like it, for its design and for its unpredictable manoeuvres that give it a life dynamics.
But I mostly wanted to build a big kite. It's kite-builders weakness : they always want people to admire their kites, and it is well-known that big kites retain more attention, or even admiration than small ones, even more beautiful or more technically incredible. "Big is beautiful", for kites. And it is great to fly a big thing. So I retained the lessons learned from my "blue bird", and I simply doubled every dimension, with a few changes.
For pictures, have a look to the presentation "L'Albatros".
So, the Albatross has a 6 m span, which is not so small, but is not difficult to transport once folded (the bag is roughly 120x10x7 cm and it is not compressed) because structure is based on telescoping 3 m fiberglass fishing rods. In fact, they are 4 m rods with the thinner, too flexible part removed.
In the center, the rods are joined by a small aluminum tube Ø 5 to 7 mm and 8 cm long, slightly folded and settled in a hole in the end-cork of the rods. This tube supports not the flexion stress of the wings lift. It is another tube, carbon 10 mm, 120 cm long that bears it. It is linked in flight configuration above each rod by a simple rubber band. In the center, a rope binder allows to choose the dihedral.
The small alu tube stays with the central body, linked with a rubber band (attention, it must not slip ; I used a slice of a moto tyre inner tube, strongly tightened). This body's bone is a carbon 10 mm tube. It does not work much, I flew with a 5.5 mm one in the beginning. But it broke several times, when falling or even on mounting the bird in a strong wind. So use a good diameter, the overweight is not so important there.
For the canvas, 3 m of 1 m wide white ripstop are enough, for the wings have a limited width. I made the tips and tail blue, the head black. I hope zoologists will not put the shame on me, but my albatross of me is a composite of albatross, common gull, black-head sea-gull, and imagination.
Method to draw the wing's shape(look to the plan, but don't copy it slavishly for all rods are not the same) :
1) give the rod its future shape with a string Ox from one end to the other.
2) use the string as Ox axis, measure perpendicular lengths and carry at scale to a drawing software or to a paper the resulting shape of the rope.
3) draw the shape you desire on paper or computer, using the rod shape as a guide. Respect as much as possible the curves and angles of my drawing.
4) scotch the rod with the string still on to a strong paper like Kraft paper or cardboard.
5) carry, on this, around the rod and again starting from the string as Ox, the shape drawn in 3.
6) draw on this model the different pieces that will have to be cut separate, then sewn together after copied on canvas. Don't forget to mark the point where your rod is tangent to the leading edge. This will be the beginning of the hem where the rod will enter when mounting.
7) cut the result in its different pieces to copy them on the canvasses.
Rods go into a hem on the external part of the wing. So, in the internal part of the wing, a thin hem is enough. But to the end, you need to add a hem wide enough for the rod to go through easily. It will be cut at 45 ° in the canvas (=bias) to allow stretching to the curve, despite the width of the hem. It has a blue part and a white part to be assembled when sewing the total (see down for the sequence). (See PS on the end for reinforcement)
Each wing has also (see rigging drawing below) two oblique stiffeners, carbon 3 mm, set in 2 Dacron sleeves, one on leading edge, one on trailing edge. Put a small link to the canvas in the middle to prevent the stiffener to move.
This is the best sequence to sew each wing :
- Cut the blue parts (reserve margins for hem at rear edge and for assembling).
- Cut the white parts (reserve margins for narrow hem on inbound part and rear edge).
- Assemble white and blue parts. Hem the rear edge.
- Sew Dacron to the wing tip according to drawing below :
- Sew the narrow hem at the inbound part of the leading edge. Continue MP=10 cm inside the future large hem to come.
- Cut the white and blue bias, decreasing width, for rod passage.
- Sew Dacron inside the blue bias at wing tip. Hem the end BB' of the white part.
- Sew the white bias in PMB along the front part on 10 cm.
- Fold A'B' on AB and sew the whole white hem except the last 15 cm.
- Assemble then the white and the blue bias in front of same colors on the wing itself (it is difficult to measure the good point before, because the bias stretch).
- Sew the blue bias till the wing tip. Cut the canvas and Dacron excess.
- Sew the Dacron sleeves of each stiffener (dacron folded in the length).
- Assemble 2 wings together (body still to come, don't believe you are finished !).
Figures (cm) indicated on sketch allow progressively drawing the total.
Some good advices :
- First make a small size paper model well to understand the 3D geometry.
- Sew together while it is flat (before sewing ABCDE) the different color parts, for instance on lines MM' and NN' if you make same deco as mine. You can also use small remains sewn together to spare canvas.
- Hem A'B'C'D'E' and A"B"C"D"E" symmetrical (not AA' neither EE'). Sew both parts along ABCDE.
- Hem A"AA' at the head, and E"EE' at the tail end, and put hems stiffeners on which the central tube will be attached (reserve a hole in A and E for that). (See PS in the end for modifs)
- Sew C'D' under right wing at 16 and 12 cm of the axis, et C"D" symmetrically on left.
This is how it would look :
The front bridle is attached to a small piece of rod NB inside the body to tighten this one, but also knotted around the central tube for more strength. The rear bridle pulls little, just tighten it to a 2 mm rod CQ inside the body, it will give it its volume. (See PS in the end for modifs)
The rigging :
The Albatross has its own rigging to give it its shape and allow it to keep this one despite the wind. It is especially necessary to allow the wings to keep their angle of attack and to have a shape that gives the kite its stability in pitch (nose up/down) and yaw (which maintains the nose in the wind direction). For this end, a wisker W1 (10 cm) is mounted vertically above each external stiffener. This forces it to curve and gives the tip the wanted shape.
W1 is the vertical wisker. B1 and B2 are the stiffeners, carbon 3 mm. Tighteners R1..4 start from top of W1 and go :
to both ends of B1, to the wing tip, to the tail (via the end of B2). A R6 tightener is attached (glued with cyano) around the small end of the biggest segment of a rod, goes through a ring at the front end of B2, continues to its symmetrical and to the other rod. My tighteners are made of an old 45 kg line, which is widely strong enough, but it must be a lot tightened, and knots are easier to do (or undo, you never know...) and less slippery if diameter is not too small.
Reminder : here is the best build I found for adjustable tighteners :
Initial set-up for the rigging :
Set-up on the field (especially the symmetry could pose some problem) :
- Have a good and symmetrical tension of the canvas at wing tip level (see "Details of wing tip" down). The canvas below B1 and B2 should be well tightened (cut B1 and B2 at the good length only when the wing is mounted). The wings canvas must show no folded zone, particularly in the area between wing tip and the place where each rod enters the hem.
- Tighten R1,R2,R3,R4 enough for the wisker B1 (carbon 3 mm) to be vertical, and B1 gently curved. R1/R2 must be tightened to the point where the rear edge canvas begins to flutter but not more.
- Tighten R6 for B2 to be well in contact to the canvas, and even gently curved.(See PS in the end for modifs)
The "usual" bridle :
- Verify each time you rebuild the bird that the two wings have the same length (the central sewing must coincide with the body tube). If not, verify the two rods have been completely extended, or correct with the tips ends strings or even by adding some "durit" to the small carbon tube of the tip end.
- If Albatross tends to fly to your right, first verify the above point. If it is not enough, lower the right wing drag by pulling the foot of W1 forward (it is the most influent set-up).
- If Albatross line is to weakly tightened in flight, or the bird tends to fly forward on top of window : tighten R3 and R4 to curve B1 more. You can also (I did) add some weight (a half-nut of lead) to the tail.
It is a 4-point bridle. I flew a long time with just a 2-point bridle. But the transversal one stabilizes the bird, and bears a small dissymmetry. It is especially efficient because Albatross must fly rather "flat" (don't be afraid, if well set-up as above, it will not fly over your head).
The transversal bridle is knotted to the rings in front of B2. My rings are in fact just made of a short piece of my 45 kg line that goes threw the Dacron sleeve of B2 and around it. Same thing for the Rx.
The transversal bridle acts geometrically by pulling forward the rear wing, but also aerodynamically by lowering the leading edge of the pulled wing, which lowers its drag. At rest, by low wind, this bridle must be loose.
For mounting, lay out the canvas, the back up, one tip in the wind direction. Partially extend the rods and block only the smaller two parts together. Introduce those in the hems to the wing tips. At the other end, position the center small alu tube in its hole. Attention to the wind that waits that moment to lift a wing and fold it to the other which is a disaster ! So when beginning, put a weight (the line bob, for instance) on the wing in the wind. Then quickly mount the dihedral tube. Only after, extend completely the rods and block them firmly : you should not be able to turn them. The curve taken by the rod tends to prevent this action, but if blocking is not enough, it will unblock in flight and I hope you have friends who know how to climb trees ! Make a mark on the rods to know if you have pulled enough. Put adhesive tape (I don't) around if you are not confident : if it does not turn, it does not unblock.
To dismount, turn to unblock, go reverse, put the rods parallel to the body tube and wrap the canvas around. It makes some folds but it will anyway, even if you dismount all riggings (I never do).
I find it a magnificent kite but you have to merit it, it is rather complex and everything is important. This said, it is very steady in flight except by very strong winds (above force 8) that distort it too much. But I could not have designed it without my laborious and difficultuous researches on the blue bird I mentioned in the beginning. I try in turn to have YOU benefit of them, sort of thanks to it...
The Albatross is not costly to build. And even if you do not have under hand an aviation hangar, no problem, you can build it in your dining-room : the width of the wing is so low it can go through the sewing-machine like a sheet-iron in a rolling-mill. You need no more a number of hours with 2 or 3 zeros, if you don't complicate your life with double-folded-hems at alveola-point (Singer sewing-machine notice, page 19).
If you want more explanations or encounter some problem, contact me (see home page). If you are a beginner and have plenty of obscure points DON'T BUILD IT ! It's a kite for experienced builders. Sure I have not all explained, especially the why's, but if you don't want to modify the model I think I have said enough. Courage, good wind, and see you on the spots !
PS of 1/1/2004, modified on 07/1/04 :
1) This article has been written in 1997/98 for the LUCANE, the periodic of the Cerf-Volant Club de France. It was also published in the NCB (of the Nouveau Cervoliste Belge club).
2) Wind limit : I flew till Force 8 without breaking. Better to stop there, because the sewings start to tear the canvas...
3) Modifications since publication :
- Body's head and tail : I have modified with a classical and more solid solution : a piece of string is sewn to the canvas and Dacron, and a transverse rod (with 2 sleeves) maintains the shape.
- I enforced the wing's leading edge with dacron because it suffers much from other's lines encounters, or being dragged on sand or rocks.
- The rear bridle starts now from the tail. I have mounted an elastic rear bridle with a 3 mm, 40 cm rubber band, and added a lead to the tail to prevent forward gliding when the line is long (and thus heavy) and the wind stops.
- I added a tightener to the B2 stiffener. Its length : just as long as the stiffener. When you pass the rod under it (don't you forget !), B2 makes now a more important curve than before, which increases stability.
- The tighteners that curve the stiffeners B1 and B2 of the wings pull no more to the canvas or Dacron, but on the stiffeners themselves, with a stop cyano-glued on them. Else the rod finishes by piercing the Dacron, especially by strong wind and rain.
- Body : It is no more pulled to a volume by the bridle. So I have put a vertical rod (fiberglass 2 mm) that allows it to keep its shape even on the ground. The ventral rod is now much longer, from the tail to the chest. So you have to make the belly canvas rounded and not angled in C and D.
- I replaced the front sleeve of the external stiffener that torn the canvas by a piece of string glued to the end of the stiffener, piercing the canvas and going around the hem and the rod. I had to shorten a little the stiffener for that.
4) To make you quiet about the feasibility of the Albatross, 6 have been already constructed by french kite-builders and they all fly well, thanks (see 4 Albatross in flight in Fetes et Reportage/Dieppe).
More : Excuse my rather poor english, but I hope it is good enough for you to understand these technical descriptions, I have no literary pretentions. Unfortunately for english speaking people, almost the rest of my site is only in french. Perhaps I will make an effort and spend some time to translate it if you consider it is worth while, but not for to-morrow... I apologize !