DR-1 (Sands): Builders Group

[nobody]

Jeff,
I also want to thank you for all the information and inspiration you share on this site, also your D.VII site. I have debated the bracing method issue in my head for a few years and as I get near starting on a project, I am glad you did the weight difference calculation for us. Your findings are as I would have expected with the brace tubing being a slight weight advantage over the wire bracing. I know you are building the D.VII, but maybee we can get a couple of people with experience reading this thread to give an opinion on the total weight issue of a DR.I. I am a nut about weight, and after much study think we can build a DR.I that would come in at 700 to 750 pounds using an 85 horse flat four engine and other modern materials. No guy's, I am not talking about a wire braced ultralight. This plane would outwardly appear as original as some of the museum planes around. For the purists that read and comment on this thread, Thank you for the research you do. Thank you for pointing out how it was done back in the day. Armed with the information you share, we as builders then can choose for ourselves the methods and details we will use on our plane. Thank you all!

[gipsymoth236k]

Knowing how originally Fokker aircraft were rushed through production AND with a HUGE mind for cost savings of time and money, why didn't the factory simply use diagonal tube bracing, thus eliminating the extra time, effort, and costs of fuselage wire bracing if it would have been cheaper, simplier and lighter? Humm...?

Regards, Gary Sewall

[greatwarpilot]

Gary - Thats a very interesting question. I think that weight aside, Jeff's comments about serviceability are key. I don't recall the exact figure off hand, but I think either Jeff or Maxim08 know what the original documentation called for in terms of a 'maintenance cycle' (for lack of a better term). If memory serves, the rigging was supposed to be checked on a fairly frequent (weekly?) basis, even by the front line Squadrons. I suspect that the ability to adjust the rigging in order to keep the fuselage true is the major advantage. What do you think?

Nobody - I'm not sure if an 85 hp flat engine would cut it for a Triplane, even at the weights you're quoting. In my mind, its a drag issue. Those three wings create a lot of lift and a lot of drag. I think you'd be hard pressed to get the tripe off the ground with 85 hp turning a toothpick prop, and even if you did it probably would not be pleasant to fly. The two Triplanes I've flown had 165 and 225 respectively (radials) and they don't feel overpowered by any means.

Cheers,

[nobody]

Greatwarpilot,

Thank you for the input concerning the drag issue versess weight.

[Von Writter]

Originally Posted by gipsymoth236k

Knowing how originally Fokker aircraft were rushed through production, with a HUGE mind for cost savings of time and money, why didn't the factory simply use diagonal tube bracing, and eliminate the extra time, effort, and costs of wire bracing their fuselages? Humm...?

Regards, Gary Sewall

As I understand it, it was because welding (Gas) was in its infancy and they were doing well to weld thin wall at all let alone with all the intersections tube bracing brings into the game. That, and it was more profitable to use piano wire.

[CORVUS]

Originally Posted by gipsymoth236k

Knowing how originally Fokker aircraft were rushed through production, with a HUGE mind for cost savings of time and money, why didn't the factory simply use diagonal tube bracing, and eliminate the extra time, effort, and costs of wire bracing their fuselages? Humm...?

Regards, Gary Sewall

There was a lecture that Fokker gave in 1923 to British Engineers on steel tube construction and cantilevered wings. He states: " The third way is to weld a small quadrant or sector of thick-walled tube in the angles, so that the whole strainer may pass through. If you wish to repair you can take out the whole wires, it is not necessary to change them. In those days we had to repair our machines more often than now,so that is why I came to this method of using quadrants. The bracing, which is standard on all Fokker machines at present , is made of a double wire, drawn through the eyelet in the corners, and tightened with one strainer only. We have used this construction for 12 years, and it is one of the most reliable parts of the entire machine and one which has not been changed during the whole time.

He also goes on to say : The temporarily assembled fuselage sides are then removed and the joints finished off, after which the horizontal tubes are fixed in place,and then the small segments in the corners for taking the bracing wire are inserted. The so-formed fuselage is then braced with diagonal bracing wires in each bay, and after being placed in a rigging jig is put into alignment by adjustment of the cross bracing concerned.

He also goes on to say that inspection is easy , with everything being visible, alterations in design can be accomplished very quickly too.

Sounds like it was used primarily for truing up the fuselage and speedy repairs. There's no mention of optional use of tube as diagonal bracing.


Lou

[baldeagle]

Originally Posted by gipsymoth236k

Knowing how originally Fokker aircraft were rushed through production AND with a HUGE mind for cost savings of time and money, why didn't the factory simply use diagonal tube bracing, thus eliminating the extra time, effort, and costs of fuselage wire bracing if it would have been cheaper, simplier and lighter? Humm...?

Regards, Gary Sewall

I suppose it's like asking why SPAD or Sopwith didn't simplify their designs either, labor was cheap and wire bracing was simply the norm for any kind of Pratt Truss structure. Fokker was a little ahead of the curve with the welded structures, but could've gone further. I think also that they didn't want to use welds in tension if possible, believing that wire in tension was OK, but trying to avoid that with welded tubing. Now we know better, witness any Pitts or Skybolt or hundreds of other more recent types. A well built all steel tube fuselage should never need straightening, and if you hammer one onto the runway hard enough to twist it you're probably going to be breaking some other important stuff while you're at it.

Brian Coughlin's Fokker Triplane with 125 Warner has steel tube bracing instead of wires and it isn't tail heavy at all, not like many of the replicas you read about. And you can't tell by looking at it.




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[CORVUS]

Very cool picture of Brian's Triplane. Ready for a morning sortee.

[Jim Bruton]

Does anyone have information on the small tabs that weld onto the rear side of the cowl ring for mounting the wooden side panels? I have seen photos in Leaman's book that shows them but unless I am missing a page in Ron's plans, I don't see them indicated anywhere. I can guess the pattern and could probably guess at an adequate number to use, as well as the hol size and rivet/nut-bolt size but if anyone has already worked this out, I'd appreciate knowing!

Thanks!

Jim

[Butch]

and they don't feel overpowered by any means.

Edward,
That is because there is no such thing as an overpowered aircraft.
Pete