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Old Feb 11, 2013, 03:06 PM
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Steve Merrill's Avatar
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That sounds reasonable Trevor. 3/16 ply will also work. Go buy your self a band saw. You can get a pretty good one at Sears, here in the states, for about $100. It will cut through anything.

You are doing a good job. This is going to be a very cool airplane!
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Old Feb 13, 2013, 06:35 AM
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35Mhz's Avatar
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Trevor,

Check out this http://http://www.modelflying.co.uk/albums/member_album.asp?a=23254

The trick here was to mount the motor through the front, but make a smaller hole in the FW, mount up the X piece on the F/w first and then Screw in the motor from Behind the firewall through the smaller hole, no problem here to access the screws
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Old Feb 13, 2013, 06:37 AM
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Nice humble table saw. I'm sure that works great on balsa.

Now I see what you are doing. I would be concerned about how close those bolt holes are to the edge. Your ply plates will help, but at high RPM, even the slightest vibration may cause problems.

I thought you were mounting the motor behind the firewall, and the prop shaft sticks through the front. Can you reverse the motor shaft on your motor? This way you would have more surface area to bolt the motor to the firewall. Your way will work, I'm sure, but I would find some way to add more security to the mount
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Old Feb 13, 2013, 06:47 AM
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DUNDAS CANADA
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Quote:
Originally Posted by Trevorh View Post
Well, the firewall is done and the motor fits! It feels pretty solid, but I still have the option of fitting another lamination of 1/16 ply to the rear face if needs be.

Now I just have to sort out how to build the front of the fuselage to blend nicely with the spinner.
Trevorh.
Maybe you can do it as I did on my North Star and others. I used 1/2 triangular balsa stock to which I made the cuts for easy bending.
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Old Feb 13, 2013, 06:54 AM
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Something Like this. On this model, I used a mount made by Himaxx. You could buy a similar mount, which makes it easy, or instead of using the mount, use the X mounting bracket you already have and mount that to the FRONT of the firewall. Then mount the motor. The hole only needs to be large enough so that it does not interfere with your motor. Good luck, this is why scratch building is fun!
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Old Feb 13, 2013, 07:46 AM
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Ware, herts. U.K.
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This stage is one of those times my workshop gets a partial clean-up as I search out all those sheet offcuts to stick inside the fuselage sides until I have enough to sand to shape!
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Old Feb 13, 2013, 09:53 AM
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Originally Posted by LADDIE View Post
Trevorh.
Maybe you can do it as I did on my North Star and others. I used 1/2 triangular balsa stock to which I made the cuts for easy bending.
Unless you have an affinity for balsa, I would just use pink foam blocks. You will spend about 5 minutes total shaping the nose after they are in place. Can then coat with fiberglass or silkspan or whatever your preference is, using either epoxy or WBPU...Pete M
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Old Feb 14, 2013, 02:59 AM
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Hampshire, U.K.
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Thanks again for all the responses guys.

Tim, The idea of fitting the cross mount permanently hadn't occurred to me. I'll file that one away for next time! It certainly reduces the size of aperture needed in the firewall. In this case though, the nose ring would still be fairly thin since the spinner diameter is only slightly greater than that of the motor.

Steve, So I am in uncharted territory after all! It was your reassurance that you had done this before that gave me the courage to give it a go. Nevertheless, even the misunderstanding has proved useful, since I feel I have learned something from the exercise and it does look as if it will work out okay. I have now applied a 1/16 ply lamination to the rear of the firewall, so it is even more solid.

Thanks Robin, Laddie and Pete for the thoughts on building up the nose. I think my approach will mostly resemble that described by Robin - bits of balsa glued on here and there until it can all be sanded down without too many holes appearing. I've never got on very well with foam and, as you say Pete, it then needs surface treatment before it can be covered and I get on even less well with brushes. I know others get very good results with this method though.

Whichever way you go, the reward for fabricating all those graceful compound curves is that you then have to persuade a sheet of heat shrink plastic to go around them, so maybe I won't round things off too much after all!
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Old Feb 16, 2013, 05:11 PM
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The nice thing about pink or blue foam is that no heat shrink is needed, just a few coats of epoxy. For complex curves, it's hard to beat. Here is a quick cowl I made up for my Northstar. It came in at about an ounce, and was way faster than a balsa cowl would have been. I started with a solid block made up of two pieces glued together with gorilla glue, then used a hole saw to shape the motor hole, removing the extra foam with a small knife and a dremmel bit. I then shaped the outside with 80 -200 grit sand paper. It sands much faster than balsa and there is no grain. I then inset the small pieces of ply to make hard points for mounting to the blocks on the Northstar pod. A little epoxy, and it was hard enough to test fly. A little finish sanding and it will be ready for paint.

Your work so far has been very nice, far better than anything I have done, so you should have no problem making a foam cowl.
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Old Feb 18, 2013, 02:01 PM
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Nice work Lupy. The only flaw in that approach for me is that word 'paint' (see here for an example of why I react so badly to the thought!)

Meanwhile, I'm making headway down the balsa-bashing route.
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Old Feb 19, 2013, 04:36 AM
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Yes Trevor, compared to that, ironing Solarfilm around compound curves is a doddle!
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Old Feb 22, 2013, 02:19 PM
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Battery Hatch

Herewith some photos of the construction of the hatch. This proved a bit troublesome - each time I released it from the fuselage, it distorted due to the stesses in the various bent pieces of balsa. Fortunately, now that it's complete, it is quite stable.

I have made a start on the front top section, but have been distracted somewhat today by another little construction project shown in the last picture.
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Old Feb 25, 2013, 05:59 AM
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Airframe complete (well, almost!)

With the front end done, I now have a nominally complete airframe, and have begun the 'prepare for covering' phase. There are still a few jobs such as making and fitting a battery tray, but that will wait until after covering.

I'll probably put the whole thing together for a last naked photoshoot before the end of the month - earlier if I get too bored with the sanding and filling!
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Old Feb 25, 2013, 02:12 PM
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Skittle? Translation for us across the pond would be bowling pin perhaps??

Looks very nice!
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