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Tiger 72.


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Yes I find aliphatic works very well and produces a good strong joint. I often use super phatic as well, it is thinner than aliphatic resin and wicks deep into the joint.

Here is some progress from this afternoon. I had intended making the forward fuselage sides from 6mm lite ply but for reasons now lost in the mists of time, SLEC were unable to produce them from lite ply and so two laminations of 3mm poplar ply were used instead. The upper longeron is balsa while the lower is cyparis - in my experience the lower longeron is more susceptible to crush damage from handling the model so I felt a little extra strength here would be beneficial.

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Yes, I'm not sure the lightening holes will reduce the weight by a noticeable amount but every little helps! If I had been cutting the parts out by hand I doubt I would have bothered but since they were being laser cut anyway it seemed a shame not to take advantage and cut away some redundant wood. I might dig the cut out pieces out of the scrap bin and pop them on the kitchen scales just to see how much difference they make.

Glad to see I'm not the only one who's started repeating himself!

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It's been a very productive evening in the shed - the Tiger is now three dimensional and sitting in its jig while the glue dries overnight. All formers and stringers have been added - annoyingly, a couple of rear formers are a bit on the thin side and needed edging with scrap balsa to fit properly in the fuselage but it was an easy fix. So here we are at close of play this evening...

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Well this is awkward... Have a quick look at the picture below and see if you can spot the mistake before you read the rest of this post...

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Did you see it? The carefully laser cut servo tray sits directly above the plate that retains the captive nuts for the wing bolts in such a way that access to the servo screws is all but impossible as it currently stands! It would have been far better to have fitted the servos before fixing the plates into the fuselage, but too late now. However, it is the nature of aeromodelling that problems present themselves and solutions must be found and so I have come up with a solution - I am going to drill a couple of small holes in the wing bolt plate that are just large enough to get a screwdriver through to tighten the servo screws. There is plenty of strength in the wing bolt plate so two small holes won't harm it. As I use the servo screws that have a hex drive end for use with an allen key, an alternative would be to use the short side of the allen key to tighten the screws as this would just fit in the available gap, however I think drilling a couple of holes will be less fiddly.

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Thanks Percy. Yes I moved the wing bolt plate forward a bit to allow me to bury the bolt heads in a thicker part of the wing. Whether or not that bestows any particular advantage is debatable but it seemed like a good idea. I also wanted a good amount of space on the servo tray forward of the servos themselves to leave space for a receiver and a cluster of telemetry sensors without encroaching on the cockpit space, thereby allowing me to fit a full body pilot and scale like cockpit detailing later on. As always, an advantage gained on one hand is balanced by a drawback on the other. For now it's easy to work around it all but I'll be adjusting the parts and drawings before making them available to anyone who wants them.

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When referring to the Peter Miller Ballerina Percy said "I notice he uses the same wing section for his designs, so I'm assuming he's happy with the flight characteristics it offers. " At first glance this seems to imply the Ballerina wing section is similar to the Ruhig Tigre, however the sections look quite different. Ruhig Tigre is much rounder and fatter at the front I think.

So probably Percy meant that Ballerina wing section is similar to Peter Millers other designs - Werewolf etc.

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The fuselage is almost done now - this afternoon I added the ply around the cockpit and made up the battery hatch. The hatch has a compound curve to it so I spent a happy hour or so strip planking it with 1/8" balsa and then sanding it back to a smooth finish. I do enjoy a bit of strip planking!

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The motor mount is made up of four pieces of 6mm birch ply. Side thrust is catered for by the mount being asymmetrical, although a little care must be taken to ensure that is assembled the correct way around - it is possible to inadvertently add left thrust instead of right. The mounting holes for the motor are offset to the left so that the centre of the propellor will still be in the correct position relative to the cowl.

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Thanks Percy. I used the double skin of balsa when I built the 60" version and although it worked well it did seem to make extra work since it effectively required the job to be done twice so I thought I'd give 1/32" ply a go this time. I carried the stringers all the way through to F4 so that the ply would have plenty of support and of course this meant there was a step behind the rear edge of the ply, so each stringer got a 1/16" cap strip along its length which was then sanded flush with the surface of the ply.

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Sorry about the unhelpful orientation of the pictures, the site seems to rotate some of my pictures to fit.

I mentioned earlier about the offset motor mount holes to allow the propellor boss to sit in the centre of the cowl...

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If you look at the picture above you can also see that the lugs on the side pieces, and the corresponding slots on the front face of the engine mount are slightly different sizes to reduce the possibility of building the mount the wrong way around.

Finally, and slightly out of order, here is a picture of F2 where I reinforced it with strips of 1/4" square cyparis left over from the lower longerons. The amount of pressure required to pull the fuselage sides together at F1 was too great for F2 to be able to withstand it unsupported and it started to buckle, so a little local reinforcement was employed to keep everything in shape. A series of saw cuts on the inner faces of the fuselage sides would also have helped but I didn't feel the need this time.

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Edited By Jim Newberry on 11/12/2015 22:00:02

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  • 4 weeks later...

Thanks Percy. I'm a big fan of lightening holes, although it has to be said that, in terms of "lightening", they actually bring very little to the party... Here is a picture of all the cut out bits piled up on the kitchen scales...

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10 grammes from three ribs.... There are 27 ribs overall so my lightening holes have saved 90 grammes. At best it's a marginal gain, but a gain nonetheless. Every little helps!

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