Many thanks to Al Bowers for this document!
Copy of letter from Flight Lt. R.C. Forbes
Thank you for your letter of last Sunday. Immediately (after) I got your letter, I telephoned Hawkridge Aircraft Ltd. (who repaired the Horten) to ask them to fix the center of gravity attachments for you. However, the Horten is now somewhere in packing cases on its way to you, as far as I can find out. All I can do us to have the proper attachments made, and I expect one to be sent me tomorrow morning to verify if it is the correct type. If it is I'll have two made without delay - only a matter of days - and shipping over to you by air. They should reach you before the Horten, I reckon.
The type of releases you require are definitely not the type which released automatically because they might release at intervals and this would not be satisfactory. The manual type is not so critical.
At the end I'll put a very rough sketch to show you how to build up the release mechanism. If I had the exact measurements here I would do it for you, but is not a difficult job once you see the release fittings and method of attachment.
You have to attach the releases on the main spar on the extremities of the center section - both at, as near as possible, the same angle so the one lever in the cockpit operates the release hooks the same amount and it at exactly the same time. This is all common sense and we perfectly obvious to you see the whole outfit.
I believe I have on the Weihe the only real center of gravity attachment in existence. The hook is situated above the skid on the fuselage, making an angle between a line drawn from the hook to the center of gravity and the horizontal of 80 degrees. The is the optimum angle as far as safety is concerned. I have had a launch to 3400 feet on occasion and 2000 feet is normal. In contest flying I only use aero-towing when it is laid down in the regulations. I prefer to sit in my machine and takeoff when I feel it is the opportune moment, and literally no time at all I'm at 2000 feet. If I fail on the first attempt I can land back at the takeoff point and be immediately off again. The time wasted aero-towing is amazing compared to winch towing, then I am sufficiently old-fashioned in some ways to view aero-towing the same way as a good yachtsman views a yacht with a V-8 engine installed - as a means of getting airborne, I mean.
Now, much nonsense has been written about center of gravity launching and one of the worst articles on the subject was written by one of my German instructors in Germany, and possibly the one to which you refer as having appeared in "Sailplane and Glider".
There is no danger at all from pilot or glider point of view if the elementary principles are observed. At no position ever on takeoff should a pilot be unable to land after a cable break or power failure. In other words at each point on the climb, especially at the early stages, he should be in such a position that if anything goes wrong, his air speed and angle of climb are such as to enable him to land straight ahead without trouble.
The same article in "Sailplane" stressed the danger angle as far as straining the machine is concerned. This is perfectly true, but it is so easily obviated by the introduction of a weak link link in the glider end of the cable. It is apparent that any strain felt by the machine in rough air conditions is felt equally well by each point along the cable. If the weak link is the correct breaking strain that must break before structural damage can result of the glider.
In the case of a normal glider I recommend a 1.4 G. weak link and for the Horten 1.3 G. link. This is based on the maximum all-up weight of the machine in question. If these figures are adhered to, and if the machine conforms to normal Air Registration Board requirements structural damage cannot possibly result, irrespective of angle or rate of climb.
The technique I suggest for C. of G. takeoff in the Horten is to hold the stick central and allow the buildup of speed to lift the machine off the ground. Hold the machine off the ground and parallel to it until about 70 kph air speed is reached. Ease the control stick back gently, maintaining air speed on the climb. The winch driver should be progressively throttling back until at the maximum height the winch has literally stopped pulling. At this point the glider is flying straight and level at 70 kph and the cable is released without any tension on it. This, by the way, is almost word for word out instructional patter at the school.
You will (be) require(d) to hold a slight forward pressure on the stick at the moment of leaving the ground to prevent assuming a sudden climbing attitude, due to the low position of attachment.
For landing I suggest use spoilers as required on the approach, keeping a 55-60 kph on the clock. When almost on the ground ease this spoilers and hold off about three or four inches from a ground and allow the machine to settle on it as the speed falls off. As soon as you touchdown keep the stick where it is and pull spoilers fully out. You'll find that this the pod will invariably touch first if you land at the stalling speed and this is the nicest way of landing. It falls gently onto his skid and pulls up literally six or seven yards.
You mention Hanna Reisch. She is a very good friend of mine and spent all of her vacations with my wife and me the last two years in Germany. We still correspond regularly.
I forgot to mention the operation of the undercarriage last time I wrote to you. Do not push the lever forward after getting airborne, but just push in the knob with your right thumb and let the lever fly forward. If you do this the wheel falls correctly. If you push the lever forward manually it does not operate correctly - at least it did not with me. For landing just pull the undercarriage handle back until the spring-loaded plunger clicks home. I hate like Hell to have to land without the front skid fully down!!!
There is very little room in this machine, primarily because it was built around Horten's test pilot who was only about 5 feet 3 inches tall. However if it fits it will fit you okay. I have an American Observer type parachute which slings very low on the back - just on your bottom. The base of the parachute fits a recess on the hood. A small packed seat-type parachute should fit equally well between your knees and bottom.
I also forgot to mention that would fitting the hood you have to operate the lever in front, under left, to lock it home. This lever also operates the safety harness. I'm only telling you these details to save your time to having to find them our for yourself.
You ask about doing a few hops first. I suggest you go to an airfield first to have aero-tow to a few thousand feet to accustom yourself to the flying the thing. The only part of the flight which might be likely to damage machine is the initial takeoff and only then if really carelessly carried out. Why, then, prejudice this beautiful machine by hopping it? Much better to get off the ground for the first time and really get used to it.
I didn't realize the climatic conditions when I asked you about flying the Wing when I get across. Of course it will be impossible but, anyway, thank you for the offer.
I am sorry to hear you'll won't be taking part in the Nationals this year, but I know by bitter experience how much it costs to keep a family, car, and sailplane. Still, I manage somehow, and I curtail the other activities to flying in contests. It is all grand fun and I meet such marvelous people.
Please let me know who's flying in Sweden this year from your part of the world. I know Paul McCready is flying a Weiher, but who else is flying what?
My wife is now in Chicago and is organizing for me my tour of the States at the end of the year. I shall certainly look you up if it can possibly be arranged. The only reasons for his two-month trip are to visit my parents-in-law whom I haven't met yet, and, of course, to visit Bishop, with hopes of flying there if it is all possible. Also to study conditions in the States with a view to settling there when I leave the Air Force - if I leave it!
You seem to be worried about how to get the Horten from Detroit MI, to Valley City. Why not aero-tow it?, and call in here and there at various air shows with it, and let it earn its keep? It is a money spinner and always attracts big crowds. This is only an idea for it is worth.
Perhaps you can assist me, since your business is my hobby. I am a keen photographer both still and movie. At the moment I have three or four reels of Agfa color movie film which I just cannot get processed in his country. There are shots of a Standing Wave at home in Scotland, one or to personal shots and one whole reel of the Horten in flight. Could you possibly process them for me, or if not, give me the address of a firm in the states who could do it for me? I will be much obliged if you could, that might be a help to you to see the films before you actually fly the Horten. I cannot tell you what they will be like as I didn't take them and the weather for photography was dreadful.
If you're interested, I use a Leica 3c, a Super Ikonta and a Rolleflex for the still photography, and a Siemens 16 mm movie with a set off four lenses. The latter is an excellent camera and I've had some marvelous results with it. In conjunction with this I have a Zeiss Ikon projector.
No more for now, but I will get those two releases off to you as soon as possible.
P.S. I just cannot draw you a picture of the release mechanism, but I'll get an accurate drawing of that fitted to the other one, which is exactly the same in every respect as your one. This will not take long I promise you.