Nieuport research

['14-'18aviationcollector]

Originally Posted by brinesharks

However they also say that Spruce is difficult to bend (in one book the author says it's the hardest to bend successfully) and another says that soft woods should not be steam bent rather soaked in water and then held to shape until dry.

Hi Bryan,

When I was working on the DH9 we steamed the rear longerons so that they could be bent and placed in a jig, to replicate the original curve. The DH9 was originally restored with the original longerons but on the Queen's Birthday weekend in 1987 a drunk Army member - I think he was a cook or a chef - crashed through the shed and shattered the DH9 into three sections, so we had to rebuild the rear fuselage. He took the corner at 45 degrees, rather than the traditional 90 degrees and obviously had no control but managed to avoid two narrowly spaced trees, and two very solid upright steel sections used to construct the building we carried the work out in. It was either a large shed or a hanger. The chances of missing those trees and the steel upright members must be negligible, let alone then proceeding to destroy a priceless First World War aeroplane. The Army of course protected him and moved him within a matter of days.

The leaders of the restoration group wanted to make a series of cuts in the back of the timber, so that the longerons could be bent to the correct shape. After a great deal of debate and heated discussion - reminiscent of some of the "discussions" which go on here - I finally convinced the team to give steaming a go. There is too much shoddy restoration work which goes on, and I was very happy to make a key contribution to some quality restoration work. I honestly believe that any restoration should be carried out as authentically as possible. Often the relevant information is available, or at the very least easily obtainable, but restoration teams often don't know any better, think it is too difficult or time consuming, or just don't believe they have the capability to carry the work out correctly.

The Spruce we used was not the best quality, and certainly fell far short of the timber used in the original longerons. The grain was relatively wavy, and the timber in general was much more solid and appeared to be more dense than the original Spruce. I have had some discussions with Ellis Walker, who is very experienced in the selection of Spruce and other timbers used in the construction of timber aeroplanes. In the near future I will conduct an interview with him, and record the results of our discussion. Having talked with him it is obvious to me that there are very many factors which need to be considered when selecting Spruce which is suitable for the construction of aeroplanes. The real experts (and I am not one of them yet) can spend a day to select one flitch, and sometimes they will not select any timber at all, even after a complete day of searching through a pile of timber, and conducting various tests.

The steaming apparatus was very simple. We used 2" galvanised water pipe, which of course we covered the longerons with, put rags in the end to prevent too much steam from escaping, and supplied steam at the other end with my Mum's kettle, which we constantly filled, to replace the water lost as steam. The steaming process took a very long time - mostly due I suspect to the relatively poor quality of the newer Spruce. It's very interesting to hear on this thread that soft woods are more difficult to steam than hard woods, but it makes perfect sense because the grain of hard woods is much more open, as mentioned. We simply nailed timber blocks onto a piece of chipboard, which I had drawn the shape of the longerons on. When I last worked at the AWM as a contractor, this jig was being used as a work bench top. I was very happy to see that they still have it, although a lot of staff there must have a hard time working out what it is. We did not allow for any over bending, which with hindsight would have been a very good idea, but the results were excellent. We were all very surprised at how well the replacement longerons worked.

Regards,

David.

['14-'18aviationcollector]

Originally Posted by brinesharks

BTW - can anyone suggest a way of cutting the aerofoil profile inside the struts? I could do it easily if they were 'through' grooves but not sure how to do stopped ones with that profile. Is it a case of using various plane iron cutters and smoothing the rest by hand/scraper?

Hi Bryan,

I am sure there would be various methods which would be suitable for creating these cut outs. When I started my apprenticeship as a carpenter and joiner I did quite a lot of joinery, and used to help the wood machinists regularly. I suspect that one of the most likely methods used to construct these cut outs would have been with a spindle moulder. It is essentially a very large router which is set into a work bench, and has a guide at the back - in the same way that a hand held router has a moveable guide to control the depth of the cut, or the distance from the edge of the timber. For specialised sections, which they very often were, the wood machinists used to create the shape of the required cut out by sharpening a piece of cutting steel with a bench grinder. If you had one for each side of the required section, you would be able to replicate the shape perfectly. You could also have strategically placed ramps which could force the timber to gradually move away from the spindle moulder, thus reducing the depth of the cut until it exits the timber. Be warned about spindle moulders - as with all of these super sized machines, they are exceptionally dangerous, and there are no excuses for any mistakes. If you make a mistake you will lose a finger or worse. Alternatively you could use a router, if you are able to obtain cutting steel which you can grind to the appropriate section. Although routers are also very dangerous, they are much safer to use, and much more readily available than a spindle moulder.

Regards,

David.

[brinesharks]

Originally Posted by j ferguson

Those look like splines in the section. Do you know what material they might be?

That's a really nice drawing. Are there a lot of other similar drawings?

john

john - here is the link to the site where I found them:

http://www.wwi-models.org/Photos/Various/Flugsport/index.html

I'm trying to stick to Nieuport research but there are some good Fokker and other aircraft sketches there too.

Regarding the splines, I'll have to read up Rozendaal's descriptions but as John McK said the spars used ply splines so I tend to think the struts were the same.

[John McKenzie]

Hi all. The hollowing would have been done originally using a " French Spindle " ....This uses a pretty standard spindle moulder , which must have a slotted shaft . Into the shaft fits a double edged cutter ( for ballance ) .The cutter is usually of 4mm High Speed Steel , shaped to the exact * shape required , thus it can easily be ground , with adaquate cutting angle ,** by hand to the drawing . The corresponding other side may be a little smaller , so that it doesn't actually do any cutting , but acts as a ballance . This being necessary as the speed is likely for this job to be about 10,000 rpm .
*..When using a cutter block and inserted cutters , such as a Whitehill or similar ,( As oposed to the French cutter as described above )..it should be noted that as the cutters are set at a forward angle to the diameter ,then their profile is NOT the same as that of the finished shape required ; the cutter shape being " generated " to achieve this in the grinding shop .**
The action of the French cutter is more of a "scraping action" than the cutting with a cutter block , as the blade is naturaly , being on the diameter , set at perpendicular to the cut .This method is used for quick /low volume /low expence manufacture and is very suitable to working curved edges using a curved guide fence or ball bearing guides , and the run out radius at the ends , will be far less than with the larger dia. circular cutter block .
For large items such as wing spars , where stop hollowing out of a larger section , requires the timber to be " Dropped " on.( a mis-nomer as it has to be fed onto the revolving cutter VERY carefully to avoid Grabbing of timber and consequental Accident ! )..then the circular cutter block should be used . ( In WWI era . they would have used a square cutter block , but this being responsible for many a lost hand , was soon replaced by the Whitehill type circular block , this in turn , being replaced some 20 years ago by the safty block and included the leading , back sloping anti-kick back cutters , but these are very expensive )..
" Ramps" are NOT used on spindle moulders to feed the work on and off the cutter ....This is a tool for use on a Router application .
Wood work machinery can be very dangerous . If you dont know what you are doing , and , MOST essencially , PLAN AHEAD the cutting opperation FULLY , an accident will be inevitable .
I have been doing precisely just this sort of WWI aircraft woodwork for some 30 years ,using the above machinery , and I still have a healthy respect for spindle and planners etc...There's no substitute for hands-on experience.
Generally , Routers are less inherently dangerous IF used with care , and if as above ,you run through the opperation first with the power OFF. For the Nieuport Strut hollows , you would not want to have special cutter shapes made to the profiles , as there are for a start , 4 different (Expensive ) cutter profiles required for these items alone , and secondly ; The rear section hollows are around 45mm deep which would be along the C/L axis of the cutter , and a cutter with such a long side cut , with dia around say 30mm widest is only safe in a fixed head machine .
The way you could do it with a router , Safely ,and relatively cheaply , would be to use a bull-nose cutter ( sperical ended parallel cutter ) of say " standard " ? 20mm dia and 25mm deep , and cut a series of varying depth trenches ,overlaping /close together ,and finish by hand if necessary ...A ramp may be used at either end to start and finish the cut smoothly and according to the drawing .
If the hollow has a " flat bottomed " wedge shape ( As appx. the trailing portion ), then you could incorporate a suitable depth runner- spacer strip tacked along the trailing edge , to raise the router base plate up to the incline of the floor of the hollow section ...If a curved bottom /floor to the hollow is needed,. then this spacer strip could be replaced at appropriate place with different thickness strips to achieve what's required .
One final point is that in order to get a good clean cut , especially in soft woods such as spruce / pine , you should always try to use High Speed Steel cutters ....These can also be readily re-profiled to special shapes " at home ".
If you use Tungsten carbide or similar , the finish of cut is nowhere near as clean as HSS, (for the edge can never be as keenly sharp ) and in general they will have to be made for you at a tool firm ( you don't want an insert flying off at 20/30,000 Rpm.with only you in the way of it ! (TCT tools are mainly for repetition work or on abrasive or glued/laminated timber ) .
Best regards ,John .

And may you have as many fingers at the end of the job , as when you started !

PS, Bryan ...I can't get that last link to " Photos/-/ Flugsport " to work ?

[drrivah]

Below is the handiwork of John Gaertner of BlueSwallow Aircraft in Keswick, Va., for steaming airframe wood. Set up with a propane burner feeding a small "camp stove" (left) and tank (left below), an unused paint can and sealed lid for boiling the water, a collector tube and funnel as water inlet (above) and a drip collector at the lower end of the tube (not in place here).

Steam line feeds steam both to upper and lower areas of steam chamber via the ~ 1" pipe running parallel to the steam chamber.

Steam chamber and feed lines are insulated. Chamber rests at an angle on two lumber feed stands to allow condensate to flow down and back, and drip is manually collected and fed back into the funnel.

A digital timer is affixed to any nearby appliance.

"Cork" at upper end retains steam.

Works well.

-pete

['14-'18aviationcollector]

Originally Posted by John McKenzie

" Ramps" are NOT used on spindle moulders to feed the work on and off the cutter ....This is a tool for use on a Router application .
Wood work machinery can be very dangerous . If you dont know what you are doing , and , MOST essencially , PLAN AHEAD the cutting opperation FULLY , an accident will be inevitable .

And may you have as many fingers at the end of the job , as when you started !

Hi John and Bryan,

Thank you very much for the additional information John. I was actually thinking this through and was about to say the same thing. Ramps would work for a router but not for a spindle moulder. Serious wood working machines are extremely dangerous, especially the large ones such as spindle moulders, jointers, thicknessers (can throw timber back at you - I had a piece of timber embed itself into the workshop door in one of the Department of Defence work shops) and the ones which make me cringe the most - large rip saws. You have to think about what you are doing every step of the way. The two machinists I worked with were both missing fingers - Brett lost his little finger and Ray lost his thumb. One of the guys at Tech College, although not a wood machinist lost all four fingers at the second knuckle as an apprentice on a table saw. As John said, please please please be very careful and I sincerely hope that your finger count is the same at the end of the job as it was when you started! Even the humble router can be dangerous, although not as dangerous as a spindle moulder.

Regards,

David.

[brinesharks]

Originally Posted by John McKenzie

PS, Bryan ...I can't get that last link to " Photos/-/ Flugsport " to work ?

Bugger - sorry, got smart and edited the HTML incorrectly! Try this link:

Flugsport articles...

[brinesharks]

There are a few threads about calculating where the CoG should be (as opposed to weight and balance calculations). I'm interested in the range the factory calculated. All the Nieuport models (that had swept wings) had different angles of sweep. This is apparently to compensate for changes in engines and fuselage lengths. I found the following in 'Les Biplans Nieuport':

French:

le centrage de l'appareil est tel que le centre de poussee de l'aile inferieure est en arriere du centre de gravite.

English(Goolge translate):

The center of gravity is such that the central thrust of the lower wing is behind the center of gravity.

Can anyone suggest what that means?

[John McKenzie]

Hi Bryan , Unfortunately this doesn't tell us much that we didnt already know or surmise , ie that the CG is ahead of the centre of preasure of the lower wing ....Unless of course ,there's more ?.........Over to You Know Who !

A better translation might read :---

The arrangement / positioning of the " Wings " (apparatus ) is such that the centre of preasure of the lower wing is behind the centre of gravity
JM

( I would question whether the writers use of "lower wings " should not have just meant to say , " the wing cellule as a whole " ? as it is obvious that the CG /CP relationship depends on position of " both" wings )

[hank jarrett]

In modern terms what the original document said was the planes CG should be placed so that the entire aircraft has a positive static margin (as was said, the CG is ahead of the CP). Unfortunately, that is kind of a "DUH!" statement since it doesn't tell you where the CP is, how to calculate it or how far apart they should be.
The CP can be found in a wind tunnel or through CFD (Computational Fluid Dynamics) but they are both kind of expensive. The alternative is a risky series of flight tests where you gently expand the envelope as you move the CG aft and test control force and pitch response. That's the way they did it in the first years. Move the CG aft, reset the stab for stable flight, measure the control response. Then repeat it again till the plane won't recover from a departure. When the plane gets wrecked, use the CG from the previous flight for all production planes.
I wouldn't recommend that process any more.
Hank