Aeromaster

[Martin McIntosh]

Yes, those ones.

I am going to take my model up this afternoon. Hope I have enough clearance on the wheels which only protrude 1/2".

[Robert Welford]

Posted by Nigel R on 13/07/2020 10:05:36:

Nigel - I'm probably missing something here, but couldn't you rotate the throttle arm on the carb so the linkage is above the engine mount. This looks as if it would give you enough room even for a link/ball-ink if you made an appropriately sized hole in the firewall.

I recently finished putting together an Acrowot XL with a 3w 28i petrol. The reason for using this engine is it's both powerful and very easy to start.

Anyway on trying to start the engine in this airframe it would not start easily - lots of head scratching! In the end I found that the linkage to the choke servo was fouling the firewall and thus didn't close the choke fully.

[Nigel R]

With the arm on top and pulled back at full throttle, there was little clearance to the firewall.

If I was using a solid pushrod I could have cut a girt big ole in the firewall, but, I was intending on using a cable. As per previous post I figured it was probably six of one when comparing making an extra support for the cable an inch or so back from the firewall, vs knocking up the bracket and rocker arm.

[Martin McIntosh]

Flown it and very pleased indeed, straight as a die and just three clicks of up so I must have done something right.The only snag was that the pressure feed from the silencer kept falling off despite a very strong fuel clip round it, but easily fixed. Tried without pressure but the motor quit when pushing down from inverted due to the low carb.

Way too much aileron throw but since I was using a lot of expo I hardly noticed. Loads of power as expected and on a stall test it did not drop a wing. Landings were a doddle, even the dead stick ones.

Why do you not simply use a wire pushrod on throttle as I suggested? You would then not need the bellcrank and the wire would not require any support.

[Nigel R]

"Flown it"

As to the bellcrank and wire, it's sort of done now, I don't see a lot of point revisiting the arrangement... next time maybe I'll do it different.

Edited By Nigel R on 15/07/2020 16:55:43

[Martin McIntosh]

Thanks, I think that my heart has at last slowed down.

I may post a thread to see if anyone has any bright ideas on how to fix a windshield to polyester covering. I need to be able to operate the switch so a canopy is out of the question.

[Nigel R]

Small brackets and small screws, I would say.

I'm planning on a canopy and canopy glue but I'm not sure how secure that would work out with just a screen.

[Steve Dunne]

Nicely done, Martin!

Great to see another Aeromaster in the sky.
They live a long time, too!

Steve.

[Martin McIntosh]

Back in the air today with a modified exhaust pressure nipple. Fine until the motor coughed so I landed, only for it to stop when the model came to a halt. Strange. On carrying it back I found that the spinner and cowl were swimming in fuel and the tank was empty. Found a huge hole in the fuel feed due to the pipe getting pinched between the motor back plate and mount. Easily solved and everything now hunky dory.

I reduced the aileron throws by removing the servos and re tapping the arms a couple of holes further in to take the ball joints. A little Tx tweaking and I now have the roll rate I want. I shall now concentrate on elevator travel and making sure that it will knife edge from one end of the field to the other.

The fairly strong slight crosswind today did not bother it at all when landing.

[FlyinBrian]

Posted by Bob Cotsford on 13/07/2020 09:51:59:

That sounds a good weight for a 62" bipe Martin. The GP Super Skybolt kits at 58" regularly came in at 9-11lbs depending on the finish and power plant, I've not weighed my WotsWot (50" but the quoted weight is 7lb.

The orange and white looks good together, you've done a very nice job trimming the paintwork and colour matching.

I think it is actually 52" span rather than 62" but 7/3/4 lb is fine - there is close to 1000 sq inches of wing!

Martin, your model looks great, make me want to build yet another.The Ferrari red against white is rather visable eh?and with the B&W checks underneath there is little chance of confusing which way up it is.

Was checking mine over yesterday, it has not flown for a while - found a/ the battery IR is high so when it is under load it drops voltage and the capacity is well down - replaced it with a 5 cell 1500 2/3 A (not AA) pack which seems to hold up.

The u/c mounting ply has got a bit fuel soaked now and the wood above it is going soft (must stop doing so many T&Gs - so looks like another refurb coming on soon

 

Edited By FlyinBrian on 18/07/2020 08:32:55

[FlyinBrian]

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 R]

Not much to show for this week's efforts.

Rudder leading edge assembled:

which fairly soon after looked like this:

Anti warp strips at root/tip.

Similarly, for elevator:

and a bit later:

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 R]

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:

Rough planed:

And near done:

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 McIntosh]

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 R]

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:

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:

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:

And I made the skid and mount plate:

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 R]

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:

Front view, corner slabs going in:

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:

Nosering back on, and out with the razor plane:

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:

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

Jubbly.

Now a big hole:

Spinner fit looks good.

Hole is too tight around the cylinder though:

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.

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

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

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

[Nigel R]

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:

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:

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 R]

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:

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

[Martin McIntosh]

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 R]

Never used GRP sheet before, must try some.

Made a start on the U/C:

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 R]

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

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 R]

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:

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 . 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!

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 McIntosh]

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 R]

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 McIntosh]

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.