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Aeromaster

Simplified version of the classic biplane

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FlyinBrian18/07/2020 08:41:03
665 forum posts
4 photos
OOPS Post removed. I have just seen Martins post re throttle linkage which was what I tried to say in words - not a thousand but too many

Edited By FlyinBrian on 18/07/2020 08:45:28

Nigel R20/07/2020 10:36:03
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4082 forum posts
694 photos

Not much to show for this week's efforts.

Rudder leading edge assembled:

20200715_230651.jpg

which fairly soon after looked like this:

20200718_230141.jpg

Anti warp strips at root/tip.

Similarly, for elevator:

20200715_230912.jpg

and a bit later:

20200718_230116.jpg

Again, some anti warp strips at either end.

Both rudder and elevator have been hinged and beveled and are ready for a bit of shaping, rounding and tapering.

Then I can get busy carving the fairing blocks and mounting them on the fuselage.

Nigel R21/07/2020 13:47:27
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4082 forum posts
694 photos

Found a few minutes to get to the workbench and do the tail fairing blocks. Standard stuff, some nice light sheet scraps stuck together and shaped.

Raw:

20200720_223551.jpg

Rough planed:

20200720_225301.jpg

And near done:

20200721_122151.jpg

20200721_122203.jpg

I still had a touch more shaping to do after that point. I'm now ready to fine tune the tailplane saddle and fix the tail end components together.

However, I might switch tack a bit and jump to the undercarriage - or at least the ply plate on the fuselage front, and get the underside of the main fuselage sheeted. I think the structure is ready for all that to go on now.

Martin McIntosh21/07/2020 14:37:40
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3542 forum posts
1220 photos

I fitted the fin first which was a mistake making shaping that block quite difficult.

For the u/c I laminated 6mm lite ply and 1/8th birch between the LE former and the firewall. This was still quite easy to shape at the front and gives a strong mount base.

Nigel R24/07/2020 11:18:53
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4082 forum posts
694 photos

Must have been nigh on impossible with the fin & tailplane in the way!

I like the laminated idea. I did something a little similar.

I used a piece of 4mm B&Q ply, which seems to be about halfway between liteply and birch ply in weight:

20200724_104219.jpg

Above that, inside the fuselage, I have two strips running widthwise (reinforcing the area where the saddle clamps will be screwed on). This is a terrible photo, it is taken from inside the tank bay, but should show what I mean:

20200722_222948.jpg

The widthwise strips are fitted between the fuselage side. The plate itself sits under. I also fitted some 1/2" triangle in the inside corners. Hopefully enough meat to hold the UC on. Now I need to splash some more fuel proofer around inside.

I also made a start on closing up the rear of the fuselage. First, the crossgrain sheeting was assembled:

20200724_104158.jpg

And I made the skid and mount plate:

20200724_104210.jpg

This will be stitched in place and epoxied, before being stuck on.

Experience tells me I must remember to put the snake outers in place before sticking the underside sheet on...

Nigel R03/08/2020 09:26:50
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4082 forum posts
694 photos

Been rather busy this last week building a shed not an airplane, so I've not made that much progress on the Aeromaster. But I did get some time at the bench to have had a go at getting the cowl in place and final fit of the motor.

First cowl blocks... the motor has been in and the nosering located and three slabs fitted behind it. Motor then comes out, some scrap sticks as reinforcement to keep things in place whilst the nosering is removed to allow easy fitting of the corner slabs:

20200726_223203.jpg

Front view, corner slabs going in:

20200728_224402.jpg

I took the nosering off - hence the circle traced around it, so the corner slabs could be left long which makes them a bit easier to fit (hence those sticks to keep the other three big slabs in place).

Finishing basic construciton with some big lumps at the bottom:

20200728_231809.jpg

20200728_231819.jpg

Nosering back on, and out with the razor plane:

20200729_221126.jpg

Made a whoops with one of the side slabs - stuck it on too low, hence the big gap - easily fixed before rough sanding with some 80 grit:

20200730_224742.jpg

20200730_224753.jpg

Smoothed out a few bumps and oddities and went over with some finer grade paper:

20200730_224815.jpg

Jubbly.

Now a big hole:

20200801_222718.jpg

Spinner fit looks good.

Hole is too tight around the cylinder though:

20200801_222738.jpg

Plus that needs lots more space around the exhaust area. Really need to sort out my exhaust hardware now. Do I use the supplied silencer (which will poke out the side a fair way) or a short flexi pipe arrangement to keep things inside the confines of the cowl (nearly) and exhausting down the centreline right below the wing? I have considered a turbo header, that might work nicely too.

20200801_222800.jpg

I don't know yet. Anyway. Last pic, close up of spinner fit (with thanks to Pete Miller for sharing the technique).

20200801_222828.jpg

Edited By Nigel R on 03/08/2020 09:29:08

Edited By Nigel R on 03/08/2020 09:35:45

Nigel R10/08/2020 09:16:58
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4082 forum posts
694 photos

Another grab bag of small jobs this week.

Just Engines did not have the turbo header in stock, so I ordered an OS header and a JE flex pipe, and opened out the cowling:

20200808_224447.jpg

20200808_224500.jpg

20200808_224518.jpg

JE also sent a neat metal bracket to hold the flex pipe at the rear, yet to be mounted as I want to get the U/C fitted first, don't want the two things fouling each other.

I also did some other cowling jobs, mainly opening up around the motor, and making needle valve access, plus started fuelproofing.

Then took a break from the front end, to get the tail end attached and lined up:

20200809_223909.jpg

That went fairly well. Need to do a touch of fettling around the front of those blocks, put some filler in at the tailplane/fin leading edge and get the control horns on.

Small steps forward.

Nigel R10/08/2020 13:19:14
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4082 forum posts
694 photos

Whoops, nearly forgot. Sorted out control horns.

I like the SLEC "big" control horns. They have a decent size base, and a pair makes a good horn for closed loop. My "engineered" answer to attaching the things is a pair of M2 x 15mm bolts:

20200810_112851.jpg

With the elevator I just screw into the spruce joiner, and as usual add a drop of cyano to harden the threads up.

Martin McIntosh10/08/2020 17:49:34
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3542 forum posts
1220 photos

Cannot remember when I last bought a horn since I always cut them from 1/16th grp with a junior hacksaw. This way I can easily get them the right size and shape for a given model. Simply riddle with holes and epoxy in after covering. Much neater, stronger and no screws to work loose.

Nigel R11/08/2020 09:54:24
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4082 forum posts
694 photos

Never used GRP sheet before, must try some.

Made a start on the U/C:

20200810_222229.jpg

20200810_222248.jpg

Another job for the K&S bender.

I'm using an 8g rear leg and 10g front. As far as I could make out that was what the original Aeromaster used. My U/C has a little less height than the Aeromaster plan shows, but I am using bigger wheels, overall, should be the same, if my sums have come out right.

The next job there is to clamp the thing in place and get it wrapped and soldered, before cutting off excess lengths and dressing the axles with a washer and a flat for the collet. Then I can finalise the exhaust mounting bracket.

Nigel R12/08/2020 08:38:46
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4082 forum posts
694 photos

I got the legs mounted to the fuselage, then wrapped and soldered last night, before the muse left me:

20200811_221428.jpg

Then I watched the lightning storm for a bit. Quite spectacular, unusual for this country, clear sky between myself and the storm cloud which was some miles away; the sky was lit with continuous yet silent flashes.

Edited By Nigel R on 12/08/2020 08:39:23

Nigel R13/08/2020 11:30:58
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4082 forum posts
694 photos

More odd jobs ticked off the list; dressed the UC with washers and flats for collets, mounted the exhaust bracket, mounted the switch on a plate inside the fuselage. Nothing particularly photo-worthy.

I started rigging:

20200813_111257.jpg

I'm lining up the C/L with the two uprights, pinned into the wing tips. The diagonals then fix the fore/aft position.

I have to allow for the thin ply strips that form the top wing saddle during this process. It's also highlighted the fact that my carefully measured and bent and soldered cabane structure is actually a bit out teeth. However, some resin and the ply will make up the difference and hopefully be all but invisible when the thing is together.

Speaking of which, it is finally starting to look like an airplane!

20200813_105207.jpg

She looks a bit long and skinny without the wing tips.

I took a quick weigh in at this point, 5lb 10oz. Missing some bits - tank, battery, covering and miscellaneous knick knacks. If she balances (ha!) that should add a pound so I think I'm on for around 6lb 10oz AUW, plus whatever the gods decree I must bolt to the firewall.

Edited By Nigel R on 13/08/2020 11:48:11

Martin McIntosh13/08/2020 11:52:09
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3542 forum posts
1220 photos

One of my cabane struts ended up a bit short which must have been the mounting because they were definitely the same length to start with. I cut it then rejoined with brass tube.

I have changed my 14x7 APC for a Falcon 15x6 wood to see if this improves the climb so will find out next flight.

The weight of yours sounds OK at this stage.

Nigel R13/08/2020 13:15:38
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4082 forum posts
694 photos

I think the lesson for me is that next time I do a set of cabanes I will need to take more time making a decent solid jig. There's a lot of work in the wire and it's very annoying to see it end up about 1/16" out.

I was planning on a 14x6 for the 81. Out of interest, what RPM does your Laser show on the 14x7?

Weight wise, there's so much wing area, even 8lb will be carried quite happily, I think.

Martin McIntosh13/08/2020 18:56:55
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3542 forum posts
1220 photos

I have never measured it but the revs sound quite low. It was previously in my Mustang so being a fast model the 14x7 was ideally suited. The wooden prop I have fitted has much wider blades than I expected so I shall have to wait and see.

A 14x6 sounds about right for your OS and I may well try one on mine.

I was a bit worried about the -1 deg. on the top wing wrt the bottom one but despite having a laser incidence meter I did not bother to measure it. The model flies impeccably so I must have got it right.

Nigel R14/08/2020 11:56:58
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4082 forum posts
694 photos

I'm going for parallel incidence between the wings. I've seen lots of variations on lots of plans, including different wing sections on both wings and different incidences on both wings and my conclusion is as long as they're within a degree or so it probably makes very little difference (unless you're flying F3A competition and actually good enough pilot to notice these tiny differences).

Last night and early this morning I got the ply wing beds attached:

20200814_104432.jpg

Apologies for terrible photo composition. Try to ignore the large cardboard box!

I first beefed up my wing tip jigs, by actually gluing them together and replacing the pins with toothpicks. Then got both wings in position and slid one of the ply strips in place. The balsa wedges were cyano'd in place to hold the ply in the right curve. Then the top wing was removed and the model flipped upside down and "an amount" of epoxy was used to hold the ply to the cabane (see photo).

Top wing back on, and repeat above process for next ply strip.

Next session I will dig out the balsa wedges and finish the epoxy fill.

Edited By Nigel R on 14/08/2020 12:00:31

Tosh McCaber14/08/2020 14:21:23
192 forum posts
24 photos

The thread's become so long, I can't remember whether anyone's powering their AM by electricity. I'm intersted to see what electrical set-up would be required- motor, esc, battery sizes?

Thanks!

Trevor14/08/2020 15:04:41
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482 forum posts
60 photos

I’d be interested in a recap on this too. I’ve just ordered the bits and pieces to build an electric version this winter. Whilst I’m happy to share my plans, obviously I can’t yet say how well my setup will work!

On a different subject, I’m trying to locate a commercial carbon fibre undercarriage for the Aeromaster. At the moment the nearest on offer is the CCU12 from Carbon Copy. It’s a bit tall, which could be accommodated by recessing the mounting plate somewhat. However the track is also some 60mm wider (30mm each side) and, whilst I can’t see that being a problem from an operational point of view, I was wondering what it might do to the aesthetics of this classic design?

Views on either topic would be very welcome.

Trevor

Martin McIntosh14/08/2020 15:09:18
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3542 forum posts
1220 photos

Don`t know if you have yet cut the actual wing tips but I made mine a bit thicker than the 3/32nd shown on the plan.

Some neat soldering there I notice.

Tosh, if my motor produces say 2 bhp then you would need a set up which draws about 80A on 5s. Why electrify a 1966 design anyway? From my experience of trying various models on both i/c and electric then i/c wins by a mile. The electric versions just would not track the same and seemed to have a mind of their own. Let`s not start a debate on this on the thread here though.

Trevor14/08/2020 15:46:13
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482 forum posts
60 photos

Martin, as you say, let’s agree to skirt around the quicksand of an i.c. vs. Electric debate! As a long time electric flyer (I haven’t flown i.c. since my schoolboy control line days - apart from an occasional go on someone else’s!), I’ve often pondered on this common observation by i.c. flyers that electric models don’t seem to fly in quite the same way.

Whilst there are some differences in power delivery (i.c. delivers more power as the model accelerates whereas electric delivers less), I wonder whether the major factor is in fact weight?

For example, back in the days of NiCd batteries and Ferrite ‘can’ motors I built a 58” Boeing Stearman. Because of the heavy batteries and limited power available, I worked really hard at weight saving and the model came in at 6lb 8oz. It flew well for a scale model but certainly didn’t have the sort of performance you’d want from, say, an Aeromaster. Fast forward a couple of decades and the Stearman, now with a brushless motor and LiPo batteries, weighs in at just 5lb 4oz. There’s lots more power available and performance is now limited mainly by respect for the ageing airframe. At times though, I do feel that it can wander around a bit more than it used to - a combination of less weight and probably me flying it a bit more slowly perhaps?

Anyway, the Aeromaster is a smaller model than the Stearman so, although I certainly wouldn’t indulge in the more extreme weight saving measures I did back then, I’d still expect to come out at an all up weight between 5lb 8oz and 6lb. I’d aim to fly this on a 4s x 3300mah or 3s x 4000mah battery, depending on how the cg worked out. I can’t recall what weight yours came out at but I had the impression that it might have been somewhat heavier? Does any of this ring true to you?

Trevor

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