Aeromaster

[FlyinBrian]

Posted by kc on 28/11/2019 12:49:46:

The original versions used engines like Merco 61 etc which are probably more equivalent to a modern 60 four stroke than a 90. Even a 60 four stroke seems maximum for a 48 inch span bipe!

All of my Aeromasters have been the double swept wing 52" versions. Early ones were powered by an HP 61 and an OS 61 FSR, both were ample power. Later ones have had OS 91 Four strokes and ASP four stroke, again ample power.

[jeff2wings]

I have both the Aamco and GP kits of this wonderful bi-plane will be bookmarking this thread ! And yes,the Bi-Fly has more than a hint of Aeromaster about it .

[Nigel R]

Jeff that's very nice, I like the black and silver flowing around the nose and tail.

Where did the canopy come from?

Well, the die is cast, SLEC are sending wood, wire and miscellaneous knick knacks and fittings, and I have drawn out plans. The wings will be following the original Aeromaster construction quite closely. The fuselage outline will follow the Aeromaster but will have construction of my own preference - rendered in sheet balsa, mainly 1/8 and 3/32 with some ply doublers up front.

I'll start posting some proper updates when things get underway for real.

[Nigel R]

Thought I should start updating this thread!

I've made a reasonable start to the construction, although I have not taken that many photos yet.

Wings first. I started by making this bagful of ribs:

seeing as there are just over 40 ribs to cut for this thing, that kept me occupied for a good while. I then cut a load of strip balsa for spars, leading edges, etc.

After I did that, in the interest of the infamous first line of any old magazine build article "step 1, cut a kit of parts", I decided that it might be an idea to make the wing skins. But before I did that I wanted to know (don't ask, I under-ordered on the 1/16 balsa sheets) what I would need for sheeting the tailplane. So, a brief diversion from the wing... I usually make the bigger fixed bits of the tail end from a sheeted framework of 1/8 x 1/4 (or thereabouts, quite often it is just a case of raiding the scrap box and seeing what I can use):

That is near 20" span. Two full sheets of 1/16 required to cover the framework. No photo, but the inside of the fin looks roughly the same. The "spar" is put where the join in sheeting is, so I can get a nice flat join when it comes time for finish sanding. The fin used up the leftovers from the tailplane.

After the tailplane, it turns out I have just (and I do mean just) about enough sheet, so I need to be careful with the wings. No photos of me joining wing skins - been done before lots of times.

There is nothing particularly unusual about the wings. I am building all the panels separately and will join with glass later. The lower wing has a pair of, er, pairs, of rear spars (a quad of spars?) to demarcate the ailerons, which I am building as part of the main structure and cutting free later:

it also needs some webs, some blocks laid in between the rear spars for the hinges, some riblets for the aileron edges, and some other bits that didn't make it into the photo below - some block at the centre to stop wing bolts from crushing the sheeting, more blocks inside the rear spars to hold the torque rod bearings, ...

I found all those bits quite fiddly. It probably took about as long to get those sorted nicely, as it would have done to plane and sand a pair of solid block strip ailerons. Hey ho. I think at heart I just like carving away at big lumps of soft stuff until an airplane appears.

Ok. Last photo for this update. At this point one of the wing skins is on. It should explain why the root rib is so chunky near the LE:

The root rib is liteply, slotted to accept the wing dowel.

The middle section of the rib well end up being dremelled away when I mount the central aileron servo. I already stuck in a half rib to form the sides of the servo well.

Since that photo, I have completed the sheeting on the lower wing panels and while the sheeting remains oversized and unfinished (and thus instantly far more resistant to workshop dings), have put them aside to move on to the upper wing.

More soon.

[Nigel R]

Perhaps another short post is worth it.

I "accidentally" put in a low bid on an EBay auction for a pumped OS 81 alpha. Turns out I was the only bidder. So the engine choice for this project has been made now. It looks a nice motor. Turned up in lovely condition. I have run it - no complaints, easy starting, good throttling, solid idle (all much like any given OS four stoker I have run). The pump is a handy bonus. Nigh on identical weight and mounting dimensions as the 70 Surpass, with nearly the same power as the 90 size.

[AndyD]

because of your posts I have just down loaded the plan as ive always wanted one,not sure when I will get round to building it due to other builds at the moment but when,i will do it as electric as ive got a nice motor set up just waiting for a air frame.

[Nigel R]

Good stuff Andy. Do put up a thread when you build her!

My swept upper wing panels are entirely conventional:

I need to think of a cunning plan to keep the trailing edge of those ribs in place while i attach the sheeting. There is a lot of unsupported rib behind the main spar. The lower wings had the aileron spar keeping things straight but these do not, there are no ailerons on the upper wing.

[Steve Dunne]

Nigel,

Strongly suggest putting ailerons on the upper wing, it gives it much better aerobatic capability.

Just build the ailerons as per the bottom wing, and use a link tie from bottom to top.

See the photographs of my aeromaster in post 20/11/2019 above.

Steve.

[Nigel R]

I did weigh up going the four aileron route Steve. However I've been quite happy with the roll response on my smaller Bi Fly which is a two aileron design, it will easily snap and spin and has a quick enough roll rate for the style of flying I envisage with this machine. Minimising the assembly required at the field was on the agenda, too.

What I eventually decided was to make sure the ailerons have plenty of area - mine are slightly wider than the original plan shows and come in around 12% of total wing area.

I'll bet yours whips round with four ailerons though!

 

Edited By Nigel R on 31/03/2020 09:25:06

[FlyinBrian]

I find the two ailerons are fine, I did convert the upper wing on one build to have ailerons but to be honest I don't think it added anything; as Nigel says it is very aerobatic on two ailerons.

[Nigel R]

Upper panel construction continues:

To keep the rear of those ribs in place, I used some scrap blocks of balsa pinned down either side of them. Skins were applied with contact adhesive (my usual method). The two swept panels are quite simple units and are going together quickly. However, there is a third panel to make for the upper wing, the centre panel of 8". This will have wing attachment stuff inside it, a ply plate with lugs at the front, and some block around where the wing bolt will pass through the centre section, it is the most complicated bit of the upper wing.

Now, the original plan shows the top wing built all as one unit flat on the board with spliced spars, but I am taking a different approach - my favourite method is to build up individual panels and then join them together when finished (or nearly finished) as if they were foam panels. Another reason, my board is not big enough to do the whole 48" panel in one hit.

I also found that I had taken a photo detailing some of the internals of the lower panel:

I am using a strip of 3/32 along the rear of the sheeting to give the TE a little extra stiffness. The three 1/4 thick riblets are there to accept the torque rod. Some infill between aileron spars is there for the torque rod bearings and the hinges.

One major goof, I used 1/16 ribs at the tip end of the panels. Normally, I use a thicker section rib there, and I should have done so this time - the 1/16 ribs have bowed a little, and will need some careful attention when I get around to making and attaching the tips.

More soon.

Edited By Nigel R on 01/04/2020 10:11:16

[Martian]

Lovely neat work Nigel

[Nigel R]

Thank you Martian

I got the other sheeting on the upper panels. All looks good. Two straight panels. That's the good news.

Now the bad news.

I went to examine the lower wings with a view to sanding the sheeting back in line with LE and end ribs (etc), and discovered a major horror on the lower wing - whilst one panel is good, I have managed to build a warp into the other panel. The TE itself is straight. But, I believe the ribs flexed around the aileron spar location and caused the panel to take on a set as I pressed the sheeting on. This means the TE is straight, but, the remainder of the panel is not. At one end the bend in the rib is quite apparent, around the aileron spar point. All in all a bit of a setback as I cannot adjust at this stage, the sheeting is on and that is that. I might need to strip back the sheeting and try again - if I can get the sheet off cleanly - although the problem there is that I definitely do not have enough replacement material. I am tempted to buy more wood and simply start over for the lower wing and do it right this time.

I guess if I had jigged the wing up with the jig strip at the aileron spar location, where the rib is nice and strong, that would not have happened. Live and learn.

[Nigel R]

Tonight's session was a minor victory.

I had a basket full of wood on the slec webpage and was ready to order, when the thought occurred i had nothing to lose, what is the worst that can happen if i try and sort the warp out?

I started by having a good look at where the warp was and figured that if i could fix a corrective twist into the two bays at each end i would be back to very nearly warp free.

Before going any further i cut the aileron free.

I then managed to slice the join between sheeting and the end rib easily enough. The next rib in was tricky to reach and the join with the sheeting was cut blind. I think i probably cut through the rib itself anyway it was enough to allow me to flex the panel and stick the sheeting back down with thin cyano.

Don't know if it comes out in the picture but the panel is now within 1/32 of flat at the aileron hinge location.

One of my nine lives gone, for this build!

[Nigel R]

[Nigel R]

Aileron have yet to be tidied up and faced.

[Nigel R]

Only a short spell actively working on the build last night, getting the ailerons ready for facing with 1/8 sheet:

the facing won't take long. Obviously I have the main panels to face at the TE as well.

I took a picture of the tail surfaces as they stand, they look just like a vanilla lump of 1/4 sheet:

both are (or will be) sheeted core (1/8 x 1/4 framework) - lighter and a bit more warp resistant than solid sheet - with med or med-hard 1/4 x 1/2 along the TE, med 1/4 x 1/4 LE. Those strips add quite a bit of strength to the core. Finished with some tips from 1/4 sheet (in this case what I had handy was some 1/4 x 1/4 strips).

In case anyone familiar with the Aeromaster looks at that and thinks something looks amiss, yes, the fin is smaller than original plan - I am making the rudder wider (I like the rudder to have some authority).

Next big job on the wings will be getting the centre 9" section together. This is the bit where the cabane attachment is done. The plan is to use 1/4 ply lugs, two of them, at the leading edge, the two sides of the cabanes will have forward facing prongs to engage with the lugs, and at the rear, a cabane crossmember will have a hardwood block clamped to it, to receive a standard 6mm wing bolt:

To make all that work, when making the centre section, I have to make sure I have a nice accurate slot in the ribs for the lugs, and I have to put some soft block filler around the area where the bolt will go.

Starting to make quite a stack of parts now:

[AndyD]

you don't hang about,i spend to much time thinking about it rather than doing it.i want to start mine but I must finish other projects first.

[Nigel R]

If only!

The log is a bit deceptive up to this point Andy, I've been putting a bit of time into this on and off for a few weeks - at the rate I build it'll be another couple of months before I'm done with the wings and on to the fuselage...

Time spent thinking about projects is never wasted, and usually winds up saving time at the end of the day.

[Nigel R]

Tonight's job was marking out the slot for the ply lugs, and making some ply doublers for the balsa ribs. Lots of careful measuring. Ready to assemble and glue up the structure now.

[Nigel R]

Slow week for the build, although the short sessions I put in seemed to move things on quite well.

Most of the time has been put into the upper centre section. After part-cutting the slots for the ply lugs, I got the basic structure - ribs, spars, webs and LE - assembled:

Very basic jigging as usual, just a strip near TE and near LE. Providing one doesn't bend the ribs (!) - see previous tribulations with lower wing - this is plenty to keep everything nicely straight and warp free.

The balsa ribs in this section have some ply doublers to help strengthen things up. The two ribs that sit over the cabanes have been made from liteply so won't need doublers. It is probably a little overkill but won't add much weight to the whole build. My thinking is that all the ribs can help out near the LE by distributing the loads from the lugs into the wing skins and the liteply rib will sit on the cabanes and help spread any loads from those at the bottom skin to the top wing skin. I usually try not to be shy with material use around the key areas where wings attach to fuselage. Strength at stress points doesn't go amiss.

On this section I stuck in some scraps of 1/16 near the TE of the ribs, in order to keep them correctly spaced:

With these in place I only had to hold the outside two ribs in place whilst doing the sheeting.

Once I had the lower sheeting in place, I added a lump of soft balsa to prevent the wing bolt from crushing the wing:

and then put some pieces of 1/4 sq (ish) next to the slots, to provide some extra gluing area for the ply lugs:

I also poked the knife through the lower sheeting to mark out where the slot will be made.

With that done I was ready to button up the panel with the upper surface sheeting.

Following that operation I tidied up the sheeting at the root and tip of all the panels, and I now have some panels that look like this:

and this:

The upper panels only need the real leading edge to be stuck on and shaped. The lower panels also need the ailerons and the torque rods to be sorted out. They are then ready for joining together.

Edited By Nigel R on 15/04/2020 10:17:22

[Nigel R]

Eight foot is a fair amount of leading edge to shape.

Phew!

[Nigel R]

Been busy (re) painting the kitchen this week, not so much play time for me in the workshop

I got the aileron facing on and the centre section cut free; both parts neatly sanded to length. The built up ailerons have come out nice and light even though they are large (2-1/2" wide from an 8-3/4" total wing chord).

Next move is to get the torque rods - and hinges (dry) - installed.

I don't know why this picture has come out all Australian.

I also thought I had a closer photo of the facing just to prove I'm actually doing something useful with the wing, as it's not obvious that I've done anything bar saw the TE in two, but I can't find it now, I think I've had a user error when using my mobile to snap a shot of my progress... Hey ho. The facing is just 1/8 sheet, which will provide just enough material to get a good taper - I'm intending to bevel both wing and aileron.

Edited By Nigel R on 23/04/2020 10:27:32

[FlyinBrian]

Beautiful building work, It's personal taste but I much prefer the two swept wings version.

[Nigel R]

Thanks Brian

Both versions look good to me, I had to pick one and this build I went for the original layout

If I build another I would very likely do the "Too" variant, I tend not to build the exact same thing more than once