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Nov 08, 2005, 02:46 AM
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A Ponnier's Progress


Okay, okay, I'll start a new thread about the Ponnier. I guess it will make the actual build details easier to find.
Just by way of a brief recap, the model will be a 50" span, 1913 Ponnier Monoplane racer. A rather chunky fuselaged, 23' 6" span mid wing type, powered by a twin row rotary engine. Although the structure will be pretty much my usual type of thing, the model is being built as something of an experiment. The idea is to build a vehicle to test out one or two ideas I've been toying around with and to provide a suitable model on which to try out the laser cut spoked wheel kits mentioned in another thread.
The ideas I want to try out are (1) an undercambered wing and (2) lateral control via wing warping - as per the original.

To bring things up to date, here is my final post from the earlier thread. The next couple of days is likely to be spent column writing, but then I'll get those photos sorted out and some more building done.

After a slight delay, waiting for the plans to arrive, ( the wonder that is the Post Office) work on the Ponnier is progressing quite nicely.
With a couple of minor exceptions, largely caused by the cutting process and now rectified on the parts file, the laser cut parts are an exceptionally good fit. This factor alone has allowed work to progress even faster than I had expected, much more easily than expected. If I thought the formers looked big, assembling the front fuselage box demonstrated just how bulky the fuselage actually is. You never quite appreciate the size and proportions of a model when you draw it in CAD and the sheer physical size of some structures have lead to a minor re-think about some areas of the model. By and large this concerns the rear fuselage framework which looked fine on the computer screen. However, once you actually see it going together, it soon becomes clear how flimsy it looks. It's a big structure and 1/8 square balsa looks awfully small by comparison.
Not having any 1/8 square bass, I've substituted obechi for the longerons, each of which is 24" long. Not overly long, I agree but with a frame depth of over 6", I'm sure you appreciate the potential for flexing problems. These have been remedied by the addition of 3/32 square diagonal bracing strips pretty much everywhere. The result is a nice, firm, but very light rear fuselage structure.
In contrast, the forward box, built from sheet balsa sides (as usual) and liteply formers went together very easily and appears to be a very sturdy structure - even before the decking and sheet fill pieces are added.
I'm not 100% sure how the wings will turn out. The spar slots are deliberately a slack fit onto the single obechi spar, allowing the ribs to be slid onto the spar without risk of breakage. That worked out extremely well, as did the assembly of the wing. It takes a little juggling to get all the ribs where they are wanted, but does go together very well indeed. My concern is that, despite there not actually being that much structure, the one wing panel that I have ready to trim and sand appears far more rigid than I had expected it to be. Hardly ideal if I intend to use wing warping for lateral control. However, I'm still convinced that it can be done and will continue along that route.
The part that worked even better than I'd expected was the under camber of the ribs. By having them slot onto a central spar, and having both leading and trailing edges touch the building board, the potentially complicated structure becomes very straight forward to actually build.
Over the coming days I'll get some photos taken and post some here, along with a sort of step by step build. Only sort of because, with so much already built, it's a bit difficult to take it apart again to photograph.

Pete
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Nov 08, 2005, 08:59 AM
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portablevcb's Avatar
Thanks Pete. It will make the thread easier to find.

With that large a wing I'm not too surprised it came out a little stiff. May need to think about a hefty servo for the warping. The undercamber will look pretty cool too.

charlie
Nov 08, 2005, 09:51 AM
Light and floaty does it
Work in Progress's Avatar
TWIN ROW rotary?! That's a new one on me! Looking forward to the thread, though it's not one I'm going to build personally - your Isaacs Fury is in the build queue as is the Brisfit for which I shall be ordering the parts from Charlie when it comes on stream. However, I ALWAYS learn things from your build threads and consider it a privilege to have inside access to the design and build process of all these types.
Nov 08, 2005, 11:20 AM
Heli Bouncer
Looooeeee!'s Avatar
Quote:
Originally Posted by Work in Progress
TWIN ROW rotary?! That's a new one on me! Looking forward to the thread, though it's not one I'm going to build personally - your Isaacs Fury is in the build queue as is the Brisfit for which I shall be ordering the parts from Charlie when it comes on stream. However, I ALWAYS learn things from your build threads and consider it a privilege to have inside access to the design and build process of all these types.
Actually the Nieuport 28 and the Morane Saulnier AI were both equipped with the double row rotary. Memorial Flight Association has a full scale restoration of the MS AI that is used for airshows. It must sound intresting when running, I've downloaded their avi of the SPAD and SE5a flying together, their SPAD is a noisey beast.

Looeee
Nov 08, 2005, 12:14 PM
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Here's a quick shot of the basic fuselage boxes posed with my Nieuport Monoplane. Remember that there is only 14" difference in wingspan between the two models.
Nov 08, 2005, 03:50 PM
a.k.a Maltone
Pat Lynch's Avatar
Twin row rotary? - I think Mr Rake just loves assembling all those little discs of ply and balsa
Pat
Nov 08, 2005, 05:12 PM
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portablevcb's Avatar
Funny, he didn't put that many discs to be cut. Probably jsut going to do the lower ones.

Never knew there was a twin row before the end of WWI. I learn more stuff in here!

Pete, I used to think 14" wasn't much difference either. Then came the SPAD

charlie
Nov 08, 2005, 06:05 PM
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Charlie,
Actually, I didn't include any cylinder parts in the original files. I asked for some Eastbourne ones - which I didn't get. Not to worry, I have 7 Williams cylinders knocking around that will do just fine. I think the extra weight may come in useful too. Only the lower 5 cylinders are visible, the battery pack sitting right where the crankcase would be. I borrowed the cylinders off the BAT Baboon for the drawing. Guess what plan you'll be getting next for cutting? True, it is the sort of plane only a mother could love - pug ugly but interesting. I just suddenly got this urge for a dark green model.
Funny you should mention the size thing, both models looked exactly the same size on the computer screen. Obviously they aren't.

It isn't the twin row rotaries that cause the problems, it's the twin row GEARED ones that are difficult to do. Engine turns one way, prop turns the other.

maltone,
I knew that someone would eventually discover my secret perversion. At least, thanks to Charlie (when he remembers to send them) I don't actually have to cut all those discs. There is something strangely satisfying about making cylinders that way.

Pete
Nov 08, 2005, 06:48 PM
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portablevcb's Avatar
Pete,

I knew I'd mess up an order sooner or later. Glad you can make up for the shortcoming.

I want to see the rotating engine with the counterrotating prop! That ought to make for some interesting flying gyroscopics.

charlie
Nov 10, 2005, 07:08 AM
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While some glue is drying I thought I might as well post some of those photos I promised.
The three fairly substantial liteply parts, firewall, battery plat and u/c brace former, certainly help make the forward fuselage nice and rigid. They were assembled first and then glued to one fuselage side. Rear former was added and then the second side. I used CA for the initial assembly, to get things grabbed while it was all still square, and then reinforced all joints with a bead of white glue.

Liteply doublers are fitted where the wing tubes fit and the tubes epoxied in place. No support is provided for the tubes because wire joiners will pass right through them, to project either side. Similar tubes in the wing panels will then plug onto the wires.
Nov 10, 2005, 07:13 AM
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Another view showing the wing tubes and doublers. It also shows the rather nice laser cut binding holes where the pylon wires will fit.

The two basic boxes ready to join. All the diagonal bracing is set below the level of the basic framework so that it doesn't show so much on the covered model.
Nov 10, 2005, 07:24 AM
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The two fuselage sections being joined. The front section is held straight by pieces of 1/4 balsa pinned over the plan while a couple of right angle pieces of wood help align the tail end. They don't actually hold anything, just make sure that it's central and square.

The most powerful servo I own, a Multiplex slimline aileron servo, fitted into the fuselage. This will (hopefully) provide the wing warping servo. The piece of wire ensures that it ends up in line with the cable exit points. The servo itself is CAed to a piece of scrap liteply. If it needs any stiffening, that can be done later.I tested the servo first by trying to hold it fixed while operating the transmitter. I failed to stop the output arm moving as normal. I fitted it this early to prevent having to fumble around inside a fully sheeted fuselage, not able to easily see what I was doing.
Nov 10, 2005, 07:27 AM
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Although the plan calls for a hollowed balsa nose, these laser cut parts should reduce the amount of carving required quite a lot. So, if you want a Ponnier the easy way, buy the laser cut parts.
Nov 10, 2005, 11:08 AM
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Here's a couple of shots of the nose pieces assembled, but unshaped - one of the inside, one of the outside. The balsa used for these parts is quite hard, which will be excellent for both strength and nose weight.
Nov 10, 2005, 11:17 AM
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Moving on to the wings, here's the ribs just roughly positioned on the spar. This will then be positioned over the plan and the ribs glued into the trailing edge notches. Then the ribs are more acurately aligned and the leading edge glued in place. There's a notch in the spar to take the 1/8x1/2 tip, causing that too to have a small amount of under camber.

A wing panel all ready to trim and sand. That little silvery thing in front of it is a 12" rule - maybe this is going to be a rather big model in general, not just a bulky fuselage.


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