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Old Feb 11, 2012, 10:20 PM
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Pete,

I've already begun planing a few more strips in anticipation of this response. While I believe the "skis" would be strong enough, they do have quite a bit of flex to them and I think they will look better with a deeper profile too.

Funny, I thought I was the one being a pain about doing it. I naturally wanted to do something more familiar to me because every time I have to do something for the first time I procrastinate doing it but I understand why you called for it and I also know it will make the model more durable which is something I'm all for. I also know that this just adds another "club in the bag" of my modelling skills and appreciate your input regarding these techniques.

Mike
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Old Feb 14, 2012, 02:26 AM
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Woohoo! The skids are done and I feel really good about how they turned out, thanks Pete for pushing me to do it. I now realize the 3x11s would not have cut it, the skids not only have to withstand landing impacts but they are also an integral part of the landing gear itself so I'm glad I used the bamboo.

I started by cutting wider strips and planing only the insides of them. I then glued the planed sides together but only up to where I wanted the tip bend to start. I finished planing the outside of the strips to true them up then bent the tip over candle flame. This is surprisingly effective and the hotter it gets, the more flexible it gets. It reminds me a little of plastic, wherever it's hottest is where it will bend most. After inducing the bend, the pieces are glued the rest of the way and planed/cut/sanded into final shape. By laminating the bamboo as Pete suggested I have a skid that is even stronger than one solid piece and didn't require a large cane.
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Old Feb 14, 2012, 04:05 AM
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Mike,
That looks good mate, I'd forgotten just how 'fussy' the u/c on this looks. They do need to have some durability because they are all that prevents the rudder getting ground away during take-off/landing - no tailskid. Worth bearing in mind if you fly from concrete. In that case it might be worth reinforcing the rear end of the skids to prevent them wearing away.

I might as well mention this now. Since we are unsure whether it should have an angular or curved forward deck, I'm happy to go either way on this. It's only one small former to alter afterall. However, if you intend to use aluminium sheet, it's probably easier to make louvres in a flat surface, rather than a curved one.
The other point about the area involves battery placement. I show it where I do because I normally mount my batteries in a semi-permanent fashion and charge in the model. If you like to remove packs for charging it may be better mounted below the motor mount. The alternative is to make the top decking the hatch, which means the batteries can be mounted that much further forward.

In case anyone is wondering why I like fixed packs, this is my reasoning. Packs are most likely to give problems if they are damaged or abused. The most likely way to damage a pack is if it moves in a heavy landing or during removal/storage. Being secured with a small amount of silicone avoids both possibilities. If you back that up by always using packs that far exceed the requirements of the model it's also highly unlikely that you'll over stress them.
That doesn't mean you need expensive, high C rated packs, just packs with more than enough capacity to do the job. As an example, a motor that pulls 30 Amps is never going to overload a pack capable of 45 Amps output. While you could use a 1500 mAh pack of 30C rating, a 3000 mAh pack at 15C rating is cheaper and gives longer flight times. The extra weight is an added bonus when balancing the type of model I prefer - short nose and relatively long tail.
Just my thoughts on the subject, but I haven't had a problem yet - in about 10 years of using LiPos.

Sorry Mike, you can have your thread back now.

Pete
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Old Feb 16, 2012, 12:45 AM
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Pete,

No apologies necessary, all good information and I say the more the better.

Thanks for the input on the nose area. I really like the look of the rounded deck but I'm going to give the aluminum a try so I think I'll keep it simple and leave it flat as you suggest unless I decide to fiddle with it ( I'm trying to resist the urge so I can keep the ball moving).

I noticed the battery placement on the plans and was already planning on making the hatch on top, it should be easy to disguise there and top hatches are so much more convenient. While we're talking about the nose I was wondering, why is there a gap between M1 and F1? My mind tells me it would be easier to position F1 if it butted up against M1 but there may be a reason it doesn't so I had to ask.
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Old Feb 16, 2012, 12:52 AM
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I've got the landing gear mounted to the plane and the few remaining bits of wire have been added. The axle is designed to function like a split axle without actually being split. It is only attached to the gear at the center where the rigging hook is and wire is used to limit the travel at the end where the addition of some elastic will give the wheels shock absorption. There is also a diagonal wire that is the key to giving this cluster of gear legs their support. The hook on the end serves as a guide for the wing warp control wires to cross as they go from the underside of the wing up to the servo.
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Old Feb 16, 2012, 01:05 AM
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Beautiful work Mike. Looks a bit like something Santa might cruise the skies in at this point.
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Old Feb 16, 2012, 03:19 AM
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Mike,
I think I was playing safe with the length of M1 - allowing for the angling in of the sides, bevelling of front and rear edges of the sides and the fact there may be a mesh screen behind F1. Also, depending on prop driver and prop, it may be neccessary to angle F1 for side thrust. All points I hoped to verify during the initial build. Let me know your precise findings and I can update the plan to suit. Bear in mind, however, that the less it shows through the grille, the better.

The only reason it is full width is to give a positive amount of angle to the sides and hopefully ensure they both angle in the same amount.

Pete
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Old Feb 17, 2012, 12:23 AM
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Quote:
Originally Posted by hoffboy View Post
Beautiful work Mike. Looks a bit like something Santa might cruise the skies in at this point.
Thanks Matt. I had a friend come by and he said the same thing when he saw it, so did the wife. Just wait until I attach the aft section, it really looks like a heli then.
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Old Feb 24, 2012, 11:28 PM
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I found a generic 5055 700kv brushless outrunner that is a pretty close match to the AXI 4120/12 Pete spec'd out on the plans (they don't make that one anymore BTW). Since the front of the motor box doesn't have enough area to use a cross mount I mounted the motor directly to the front of the box and made this part removeable in case I ever need to service the motor. I tried a Xoar 17x6 wood prop and a 2s lipo drew 32A producing 225W while a 3s drew 30A producing 335W, this is right in the range Pete had planned on flying this plane with. I'm still not sure what the AUW will be so I'm waiting until the last minute to finalize my battery selection based on power and weight requirements.

To further improve access to the motor I also made the front grille removeable by using some toothpicks for alignment and a couple rare earth magnets to keep it in place
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Old Feb 24, 2012, 11:48 PM
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Pete,

I started sheeting the bottom before adding the aft sections and ran into an interference issue. The plans show 3/32 balsa going between the ply sides and over the landing gear wire but by the time I bound and soldered the landing gear assemblies there wasn't enough clearance for the belly sheeting so I opted to place the sheeting on the edge of the sides instead. This difference is easy to deal with up front but I'm still scratching my head a little on how to feather this in to the aft section. This also exposes the end grain of the sheets so i'm thinking about laminating the cockpit ply sides with 1/32 balsa to clean things up.
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Old Feb 25, 2012, 03:20 AM
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Mike,
I have the impression I wasn't actually intending to sheet over the wire parts, just up to them and then use some filler - or scrap balsa over the wires.
However, you have highlighted the fact that I need to alter the wire parts slightly - extend the central V parts so they solder to the front or back of the main wires, rather than below them. That should keep them within the 3/32 depth of sheeting.

I see no reason why you shouldn't be able to feather your sheeting into the longeron at the rear. Similarly, a little filler and some sanding should take care of the end grain issue.

I like what you've done with the motor mount.

Pete
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Old Feb 25, 2012, 11:47 AM
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Hey Mike, out of curiosity, how long are those four screws holding the motor mount face plate to the box? It's a very clean and elegant solution, but I'm thinking about vibration and torque. (And I tend to be paranoid, as you know.)
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Old Feb 26, 2012, 12:52 PM
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Quote:
Originally Posted by hoffboy View Post
Hey Mike, out of curiosity, how long are those four screws holding the motor mount face plate to the box? It's a very clean and elegant solution, but I'm thinking about vibration and torque. (And I tend to be paranoid, as you know.)


Matt,

You bring up a good point, they are mounting screws that came with the JR servo I'm using for wing warping and are a little over 1/2" so they go all the way through the basswood. I was more worried the basswood might not hold the screws well enough so they are soaked with CA and I figured the epoxy and glass cloth would keep them from splitting. Since the mount face is recessed into the box I'm not concerned about torque but I think I'll use a little tip Pete gave to another builder and use a spot of canopy glue on the heads of the screws to keep them from working loose, it keeps them from turning but peels off if I ever want to remove them.
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Old Feb 26, 2012, 01:23 PM
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Pete,

I have a couple questions regarding finish. Firstly, I started fiddling with some aluminum flashing for the nose and think I can pull off the louvres. My problem is the aluminum is fairly soft so it gets small scratches on it as I'm working with it. I've been experimenting with fine grit sandpaper and small wire wheels to see if there is a way to put a uniform finish on it that looks good but nothing satisfactory so far.

The second question invloves covering. I've decided to use dyed medium K&S silkspan and nitrate dope but am unsure what color the model should be. I know many have used tea to obtain a linen color but the plane in the pictures looks darker and none of the underlying structure can be seen. The white lettering on the tail shows quite a bit of contrast as well so I'm contemplating using coffee or something darker than the tea to get the desired finish.

Any thoughts on this would be appreciated,
Mike
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Old Feb 27, 2012, 03:12 AM
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Mike,
If you can get it ( I got some on ebay a while ago) litho plate is good. The thicker stuff works best because it seems to be less brittle and can be used on its' own because it's strong enough.
Whenever I want to apply an 'engine turned' finish I use a small piece of green scourer glued to a small grinding disc in a Dremel. Apply the finish, before cutting or making louvres, by lightly holding the spinning scourer to the metal to form rows of swirls. No doubt random turning could be applied by moving it around the surface.
On my Eastbourne Mono, lacking litho plate, I used an aluminium platter - those disposable, thick foil type trays. There were no louvres on that but it does work very well indeed. Maybe the application of a little GRP inside the louvres would toughen up those areas. (about 1/3 the way down this page http://www.rcgroups.com/forums/showt...=389811&page=6)

As regards colour, virtually every illustration (drawn) I've seen shows a sort of clear doped linen finish - as per my models. I put ply panels on the first one, but that was just because I liked the way they looked. A cream finish certainly 'feels' right.

Pete
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