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Aeromaster

Simplified version of the classic biplane

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AndyD29/06/2020 17:18:52
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771 forum posts
553 photos

thats very nice,i might still have to build one.

Nigel R30/06/2020 07:21:15
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3987 forum posts
722 photos

Superb, Martin.

You've probably thought of it already, why not use an acorn nut instead of a spinner? Might help move the CG back a fraction.

I've sanded the front off and made a start on my rear deck; I still have one former left to make before getting the sheeting attached.:

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Martin McIntosh30/06/2020 10:28:48
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3472 forum posts
1216 photos

I have a couple of alloy nuts from large electric motors but when I tried one on my Stampe it just unscrewed the moment I touched it with the starter, so no good. They can also bottom out inside the starter cone. The spinner shown was picked at random because it fitted over the prop and I shall probably file out a much smaller one.

Nigel R01/07/2020 09:56:08
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3987 forum posts
722 photos

Fair point. I have to admit not using one for anything above a 40 size two stroke in anger.

Not much progress to show for last nights labours:

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The rear decking sheet (3/32 thick) is on and ready to receive a soft 1/4 top cap.

Those six scrappy looking crossbraces are just temporary things to keep the top of the sheet straight until the soft top is glued in place. They will be knocked out when that is on.

The lower side of the sheet could fit better - there is a gap. My fault. Never mind. It is stuck fast, on the inside, against the top longeron - so structurally ok. The gap can be filled. File this under "must try harder".

There must be a better method of doing this particular part of a fuse. The main problem is that the taper and the curve conspire to make the sheet wood bow out and resist staying in the "right" place.

In the past I have used the softest 3/8 sheet I could find and just sanded it back to a nice curve. I may yet revert to doing decks in this way.

Martin McIntosh04/07/2020 18:44:21
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3472 forum posts
1216 photos

A fair bit more done now, although most of the time was spent on installing servos, making extension leads and getting those through the holes in the ribs. Today I have fitted and soldered up the u/c and spats which can still be removed for painting. No need for any bracing here because it is as solid as a rock. I thought that the cowl fitted OK but it was not so and have added some 6mm lite ply to the rear, much of which can be dremelled away later. Rx, switch, batteries and all wiring done.

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Sorry about the out of focus shots.

Nigel R06/07/2020 09:10:33
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3987 forum posts
722 photos

Those spats look smart. Mine will be a little more agricultural in that area, some big wheels for grass field.

I've been installing servos too, although mine are in the conventional location. First job was fitting the bearers, these are 1/2" wide liteply strips, backed with some hard 1/8". They rest on some scrap balsa rails which both located the rails, and provide more gluing area; these were carefully positioned using the most basic of jigs (1/2" wide piece of scrap balsa) to get them parallel to the top of the fuselage side. To get the rails spaced correctly I pre-mounted the servos to them, before dropping them in place and tacking with cyano. Then servos out, and glue the joints properly.

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Next up, time to get the control runs in place. I start at the back and work forward. I have a hi tech drill jig to make the exit hole. A piece of sharpened steel tube is the perfect drill:

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And inside that hole, some soft thick sheet to support the snake exit:

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There, looking good so far:

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Then sort the other end. Servos in to get the location right. The elevator snake just passes through the former. I also added some scrap thick, soft sheet, to provide extra support:

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I did the same with the guides for the closed loop rudder (snake inners from cheap snakes), and added some intermediate support pieces every few inches:

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And presto:

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I realise, since doing this lot, that I may not have left enough space between the elevator servo and the end of the snake - should have around 3", I think I have about 2" - I will need to cut the snake back and add some new support blocks - but as everything is in place this will be an easy job.

Next session proper will be on the throttle linkage.

Edited By Nigel R on 06/07/2020 09:16:58

Trevor06/07/2020 10:15:12
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453 forum posts
57 photos

Just thought I would let you know that, probably due to following these builds, the Aeromaster now heads my shortlist for next Winter's build project. I'll just be lurking for a while but then brace yourselves for a load of 'why did you do it that way?' questions!

Keep up the good work,

Trevor

Nigel R06/07/2020 14:22:15
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3987 forum posts
722 photos

Lurk away! smiley

Just bear in mind I have gone a little off-piste with mine.

Martin McIntosh06/07/2020 16:26:06
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3472 forum posts
1216 photos

Looks fine. Not a problem on this model but when I am using my normal closed loop on rudder I raise the servo a bit so that the wires go above the elevator one. Helps in tight spaces.

My cowl has been a problem to align. Thought I had it right but not so and by the time I had sanded bits off the rear end the motor was sticking out more than intended so I cut a disc of 6mm lite ply and glued this to it; also removed quite a lot of material to save a bit of weight up front. Rather than add filler to the imperfections I have tissue covered it. Lots of sanding but it is now perfect. The spats seem fine without doing this.

I intend to paint these parts with matt white Humbrol enamel as a base but am a bit low on it so may use Halfrauds white primer which I already know from experience does not go too well with the water based Ferrari Red but I think that I can get round this. I really need this wind to drop so that I can spray outside.

I have not yet dared to assemble it all again to check on the cg so shall wait until it is completed.

Nigel R06/07/2020 16:55:43
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3987 forum posts
722 photos

Yes the raised servo is a useful dodge finely engineered solution. smiley But as you say, space not at a premium here.

I'd usually go with two rows of servos on something this big, with the closed loop in the rearward "row" and throttle and elevator in front. But your CG comment made me think that all of them at the back of the wing saddle might be better. There's lots of width in this fuse to provide clearance for the output arms.

I'm expecting/preparing to have to mount the battery behind the wing somewhere. Maybe up in the decking, somehow, if I can fix it on a plate for install/removal, or in a box right behind the TE.

Martin McIntosh06/07/2020 18:07:48
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3472 forum posts
1216 photos

Cannot remember what you are going to power yours with but my Laser 80 is pretty beefy which is why I put the servos in the rear. Fingers crossed.

Nigel R07/07/2020 08:50:56
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3987 forum posts
722 photos

OS 81, which comes in about 3oz lighter than the Laser I think. I'm not planning on a radial cowl either, just a regular light balsa block job. The OS is still a fair lump for this size airframe.

Last night's short sessions - I moved the end support block and there is now 2-1/2" from servo disc centre to the snake outer - happier with this:

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Martin McIntosh09/07/2020 19:51:35
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3472 forum posts
1216 photos

One up for grabs in the "Latest For Sale" ads for £75. Looks OK to me.

Martin McIntosh10/07/2020 17:28:00
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3472 forum posts
1216 photos

Nearly there now, just the cockpit to sort out and wait for the fuel proofer to harden off since it was only applied yesterday. The cg as expected is a little forward but only about 12-14mm. The cowl needs a little packing at the rear to get it to align with the spinner but that will wait.

Some picks before I try to wreck it. Quite chuffed with the outcome.

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Martin McIntosh10/07/2020 17:51:34
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3472 forum posts
1216 photos

Almost forgot. Final dry weight is 124oz, 7 3/4lb, 3.5kg. More than I expected as usual.

martin collins 110/07/2020 18:31:58
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429 forum posts
199 photos

Very nice, you`ve done a good job there, no wing struts?

AndyD10/07/2020 19:12:28
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771 forum posts
553 photos

looks fntastic

Martin McIntosh10/07/2020 19:34:40
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3472 forum posts
1216 photos

Those wings are so rock solid that struts should be superfluous I hope. It also means that to assemble I shall only need to fit six bolts. The u/c and cabane struts are similarly rigid so I decided not to add any unnecessary weight. Glad that you like it. Can anyone else who has one of the 62.5" version tell me the AUW of theirs please?

Nigel R13/07/2020 09:40:05
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3987 forum posts
722 photos

That looks brilliant Martin. Some very neat results on the cowl and spats.

Martin McIntosh13/07/2020 09:47:25
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3472 forum posts
1216 photos

Thanks. I have added 55g of lead to the tail, swapped those lousy 5mm wing bolts for 6mm since one actually snapped when tightened and set up the throws, rates and expo. Trying to figure out how to glue a windshield to the covering film, otherwise it is ready to fly.

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