Aeromaster

[Trevor]

Hello Martin. Yes, it's only the straight wing that has a touch of dihedral. Presumably this was taken out with the swept wing on the basis that wing sweep has a similar effect (at least when upright!). That said, the dihedral is very modest and I doubt it will affect things very much - and I'm rubbish at knife edge anyway!

I'm not going to fret too much about the weight on this one. I've got a number of fair weather flyers already so one that can shrug off a bit of turbulence would be no bad thing. The choice of upper wing fixing method is one of those decisions that will have to be made in the next month, so watch this space!

[Graham Davies 3]

Morning Gents,

I found this build thoroughly inspiring and hugely helpful. So much so that I built a model that was inspired by the Aeromaster, but hinted at other biplanes that tickle my fancy. Whilst not directly related, some things may help your build Trevor:

Weight; Mine is about the same size at 47" and weighs 5 lbs 4 Oz so is lightly loaded at 15 Oz/ Sq ft. It's very similar in proportion to my WotsWot and that is 6 1/2lbs. Both fly really well, so I wouldn't worry too much about the weight.

Power: I have a 4250-560kv running 4S. I need to experiment to find the best propeller as I suspect there is more performance to come. At the moment, I have a 16x6 up front. It has plenty, but it's not going to satisfy the rocket ship flyers.

Top wing attachment. This is the bit I thought you might be interested in. I am sure I saw a similar approach on this, or another thread on here. I too hate making the wire structures. Small bend errors cause problems and getting it all lined up is frustrating work. So, I elected to permanently fix the top wing to a removable deck that fits to the fuselage with a pair of dowels and wing bolts, exactly as a high wing would. I used 3/32" lightly ribs in the top wing in pairs with a 1/8" gap, and used 1/8" x 1/2" spruce to make up 'N' shaped cabane struts. These are then glued together. Rigging is dead easy; fit the top wing (the bolts fit from the inside), fit the bottom wing in the normal way. Interplanes are merely trapped between the wings in slots. It seems to be plenty strong enough and setting alignment was really easy: Set the deck section on the bench, apply glue into the slots in the wing, whack it together and using a ruler and a spirit level, tap the wing until it lines up, Proof of the pudding was that this was the first model I have ever built that needed zero clicks of trim!

I can send pictures of this if it interests anyone.

Good luck with the build; everyone's models on here put mine to shame, but inspire me equally!

Graham

[FlyinBrian]

"I can send pictures of this if it interests anyone."

Yes please Graham - Love the colour scheme

Edited By FlyinBrian on 02/10/2020 12:05:48

[Graham Davies 3]

Thank you Brian.

Note to self: lining up the checks on the ailerons once you have shrunk the wing is, er, challenging...

Here's some pictures from various stages of build showing the rough idea of the removable section.

If you need anything specific, let me know and I'll take some more.

Graham

[Trevor]

That’s definitely a different approach Graham! I do like the idea, however I’ll probably have the front portion of the upper fuselage removable as a battery access hatch which might complicate matters. The former positioning on the Aeromaster is also a little odd - there’s no former at the wing leading edge, for example. Add to this the fact that my electric motor is much shorter than an i.c. engine, so the firewall really should be moved forwards, and it’s clear that this whole area is going to need a bit of thought.

I’ve still got a few cap strips to fit before facing up to all this though 🙂

Trevor

[Trevor]

That’s definitely a different approach Graham! I do like the idea, however I’ll probably have the front portion of the upper fuselage removable as a battery access hatch which might complicate matters. The former positioning on the Aeromaster is also a little odd - there’s no former at the wing leading edge, for example. Add to this the fact that my electric motor is much shorter than an i.c. engine, so the firewall really should be moved forwards, and it’s clear that this whole area is going to need a bit of thought.

I’ve still got a few cap strips to fit before facing up to all this though 🙂

Trevor

[Graham Davies 3]

Trevor,

I left the bulkhead where it was on the original IC design as it was in a good position to use for the forward dowels. I then used Richard Wills' idea for the motor mount, which is to make a combined battery box/motor mount which fits through a square hole in F1 and F2. This can then be slid back and forth to get a good spinner gap. I made this in 2 pieces so I could mount the battery underneath, and had the option to bring it forward under the motor to help balance. The battery hatch is then underneath, hinged and retained with magnets. I'm happy to turn her over as it means the prop can never accidentally spin up due to the presence of the ground!

Graham

[Nigel R]

Graham your bipe looks excellent

And a very neat idea for top wing retention.

I've looked at mine a couple of times since parking the project and I think I'm in for a small bit of work sorting out my rear cabane xrossmember.

Like you say the wire work looks great but can be very fiddly. Small errors seem to easily add up and then need correcting later. I think the trick is that you really need to make good jigs to work with. One area where a kit would really score.

Trevor good to hear another aeromaster is on the go.

[Graham Davies 3]

Thank you Nigel, that's kind of you to say so.

I am preparing a project for a 36" lightweight DR-1. It was thinking about this that led to the cabane idea. I'm going to do similar with the DR-1 but the middle and top wing will be permanently joined. It hopefully will be a lightweight for calm evenings.

If it works, I'll share, otherwise I'll keep quiet!

Graham

[Trevor]

Even though the lower wing is still on my bench, it seems that I've mentally moved on to the fuselage and wing attachment - I woke up this morning with various upper wing fixing methods whirling around in my head!

Most of these thoughts were not fully formed and didn't stand up to conscious examination however one which came to the fore was an approach I'd not contemplated before (at least not for this model). I'm thinking about permanently attaching the centre section of the upper wing to the cabane structure, and then using a plug-in system for the outer panels (probably steel blade in brass box). Although I've never done this on a biplane before, I do have variations on this theme on mid wing aerobatic models and several gliders and it seems to work perfectly well.

What does the panel think?

[Graham Davies 3]

Morning Trevor,

It will work, but does it give you anything? I think you'll still have many of the headaches of a wire cabane structure and all the associated challenges of getting it accurately lined up. I went with a permanently attached top wing, upper deck so I could glue the two together and get it lined up without needing to rely on my dubious bending/ soldering skills!

How are you thinking of making and attaching the cabanes?

Graham

[martin collins 1]

Hi Graham, do you have a picture that shows how the N struts fix inside the plane, does the decking bolt in to the fuz at the cockpit end, i see the dowels at the front........

[Trevor]

Thanks for the prompt response Graham. I have a dodgy back so rig my models on a table-mounted stand and try to minimise the amount of manhandling required. The plug-in approach avoids the need for inverting the model to fit the upper wing (Yes, Martin, I have remembered that your method achieves that, too!). I do have some steel blade/brass box joiner material in stock that should fit nicely between the spars so, at first sight, it should be easy to set up.

The cabane wires will probably be transverse, as per the Super Aeromaster plans so the transverse wires will be recessed into the underside of the wing and secured with flat saddle clamps (fishplates?). The lower ends of the cabane wires are attached to the inside of the fuselage sides so, by deferring that operation until the wing can be mounted on the top might (!?) make the alignment process a bit easier.

This particular decision is still a few days away though. Today I hope to make my mind up about the approach to the nose section, the wing seat doublers, undercarriage mounting etc. So that I can make a start on cutting out fuselage sides and formers.

[Graham Davies 3]

OK Trevor, that makes sense. Mine does indeed need a bit of handling to rig, but is quick and doesn't need small screws. It goes like this:

1. Fit the top wing by fitting the upper deck section. Secured from inside the lower wing opening with 2 wing bolts
2. push the interplant struts into the slots in the upper wing
3. connect the aileron servo leads, and fix the lower wing with 2 wing bolts. Before they are fully tight, insert the interplant struts into the slots in the lower wing
4. Connect the aileron joiners.

Martin, I don't have too many before it all got covered up!

You are correct, it fits to the front former with 2 dowels, and bolts from the inside of the wing cavity. Reason for this is to hide the wing bolts and avoid complication of reaching them through sheeted, curved deck.

The deck part is a 1/8" ply former up front to provide a solid base for the dowels, with lightply base and lengthways strengtheners. The rearward former is also lightply. I lined the N-Struts against the strengtheners and marked the position and then made a hole in the base to engage the ends of the 'N's. I then clamped and glued them to the lengthways strengtheners and the base holes before adding a strip of 3/16" to the base between the outsides of the 'N's and the edge of the base. This gives extra strength to the Cabanes, and gives me something to secure the end of the sheeting to. I added a former in the middle to support the sheeting, and that was about it.

To fit to the wing, the cabanes fit into slots between lightply ribs. I set these during the wing build by using a piece of scarab cabane wood (with the 1/32" ply doublers added for spacing) covered in cling film as a spacer. as a result the fit is a close interference fit, which makes rigging easy.

Rigging was dead easy; I clamped the deck to the bench and slotted the wing in. I made some spacers to fit under the wing, and put pins in the centre of the leading and trailing edges. I simply tapped the wing until it was level, and then measured from the leading and trailing edge pins to the bench until I had the required 0degree incidence. Double checked all this, and then again with my engineer's level, and let it all set!

These pictures may help.

Graham

[Trevor]

Thanks for the extra detail, Graham - and that last picture is also timely, as I contemplate how I’m going to tackle the front of the fuselage!

[Martin McIntosh]

Best of luck but complex solutions to the simple fitting of a short span wing.

Best to buy a car into which it will fit in one piece (with tongue in cheek).

Seriously though, one of my struts was of the incorrect length so I cut it and rejoined with soldered brass tubing, so maybe they could all be done like that to guarantee a level wing. Mine has no need for cross bracing and the u/c has none either.

[Nigel R]

If I was going again, I would build the top wing with the same sort of single, central cabane arrangement as my BiFly has - but made with aluminium strips bent into the upside down V shapes. Bolt the strips to the outside of the fuselage into some ply or hardwood blocks with T nuts (or similar). Use two nylon bolts right through the wing so you access from above, with a nut epoxied to the top of each cabanes - the point of the 'V' could actually be a flat about 1/2" wide to allow for the nut.

Interplane struts keep everything perfectly stable.

The BiFly arrangement is an impressively well thought through bit of engineering that minimises assembly, but relies on the kit's supplied cabanes, which of course came pre-made with nuts soldered in place on some plate which was soldered to the wire cabane. Bolts then attached from front and rear through several ply lugs.

Impressive bit of design work actually.

Or I'd make wooden cabanes and use rubber bands!

[Trevor]

No flying so far this month so I’ve had some productive time in the workshop. Sorted out the lower wing and undercarriage fixings today, so it was time for the first ‘bench fly’ pic!

[Trevor]

My October diary entry is now online:

http://www.bartonhewsons.uk/home/modelflying/sport/aeromasterdiary.html#October

Trevor

[Martin McIntosh]

Just comes up `not found`.

[Trevor]

I never did get the hang of this forum. Let’s try again:

**LINK**

Trevor

[Martin McIntosh]

Some parts of this can be a devil, can they not. The wing tips gave me a bit of an unexpected headache too.

So far my method of wing attachment has proven to be fine.

[Trevor]

Yes, I reckon the parts count for the wingtips is over 30, and they all need shaping, tapering or otherwise fettling. They look good when done though.

I still don't really know why I went off the three piece upper wing solution but, once I'd worked out a way of drilling the beech blocks to take the threaded inserts, the new method seemed to come together okay. Mind you, the parts count probably exceeded that for the wingtips by the time it was done!

I'm trying to build a bit of air into the tail surfaces, in the hope that this will give me a bit more leeway when it comes to battery location. I have read of Aeromasters occasionally coming out nose heavy but that was with chunky four strokes up front. I'm pretty sure that my cheap outrunner electric motor will be a lot lighter.

[Trevor]

I've just uploaded the November entry in my Aeromaster build diary:

**LINK**

The airframe is pretty much complete. All up weight, with just the covering to go, currently stands at 5 - 5.5lb, depending on how big a battery is fitted.

[Martin McIntosh]

Looks pretty good to me. You will like I am certain.