Two Wings and a Round Engine

[bert baker]

[bert baker]

[bert baker]

Hope this helps anyone

[bert baker]

Solartex glue side up,

Thread laid across and bonded onto glue side of tex with Balsaloc

when dry strips cut with straight edge and rotary knife

wider cap strips ripped down length from tex

iron on the thinner strips glue side down

then put wider cap strips over the top

[David P Williams]

Thanks for that Bert. I wasn't actually asking how to do it, I'm aware of the various methods and have used some of them in the past as seen on my Chipmunk -

I was just musing on the vast mileage of tape on the Stearman, the faff and cost of doing it and the weight added - it's almost like covering it one and a half times.

[David P Williams]

Well - a big heavy box of wood has turned into this..

Still a long way to go, but I've really got the building mojo back now.

As it stands in the picture with just the engine fitted and a couple of servos, it's 8.5kg or about 18.7lb. The plan recommends some modifications if using a larger/heavier engine than the Laser 180 shown on the plan. I've done the first of these, adding spar webs out to the interplane strut mountings but still need to do the second which is fibreglassing the wing joiner boxes. I've also beefed up the end ribs of the centre section that carry the upper wing joiner and bolt to the cabane struts.

Next up is sheeting the centre section and then lots of measuring and incidence checking before drilling the cabane struts and fixing them in place.

[john stones 1 - Moderator]

Impressive mojo there David, beautiful.

[David P Williams]

Now built and sheeted the centre section, and been doing a few time consuming jobs. I wasn't too happy with the end ribs on the centre section, they support the wing joiner and are bolted to the cabane struts, but they are fairly well fretted out and didn't look strong enough, so I cut non-fretted versions from 3mm ply and laminated them to the kit ones. Seems pretty solid now.

There are a load of vac formed parts in the kit, including the fairings for the rear corners above. The usual fiddly careful trimming to get a decent fit.

The cabane struts are suppiled pre-bent, and are pretty accurate with just a litle tweaking needed. They are 3/4" x 3/16" aluminium or dural and look a bit agricultural.

The full size has streamline tube struts, so several hours with files and emery has them looking a bit more realistic.

Next job is lots of tweaking, eyeballing and adjusting so that the centre section is parallel to the bottom wing from the front and from above, and at an incidence of 3.5deg to the main fuselage longeron, before careful marking and drilling the bolt holes to line up with the captive nuts already in the centre section.

[Jon H]

Looking really awesome. And regarding the laser on the plan, its a fantasy. These models always end up at 20lbs or more and the 180 simply isnt man enough for that, not if you want any sort of aerobatic performance. We recommend our 300 as a result, which often shocks customers who call to order a 150 for it as that is what they recommend on the website.

[David P Williams]

Not much progress unfortunately. Been fitting wing servos and linkages.

 

 

I was going to 3D print some mounts for the HS645MGs, but then I found these on Ebay - super lightweight and made to fit these servos.

 

 

A few mounting blocks and the are hatches fitted. I'll replace the Pozi screws with slotted ones to look a bit more in keeping.

 

 

Just got to wrap the wing joiner boxes in glass cloth and epoxy to reinforce them and fix the wing retention straps, then the wings are ready for covering.

 

[David P Williams]

Well - months have gone by, life has happened, my building and flying enthusiasm disappeared, and not much was done on the Stearman.

 

Now however I've had more time available, coinciding with better weather, and have been out flying and even joined another club that is closer (only 25mins away rather than an hour to my main club). This entailed some servicing and rebuilding of the squadron, and the Stearman has still been sitting sadly in the corner.

 

This activity has helped to rekindle my enthusiasm for this build and I've been tackling several daunting or head-scratching jobs that were stopping my progression.

 

The first was setting up the centre section. The lower wing incidence, dihedral and perpendicularity to the fuselage are all set by the pre-cut parts and the wing joiner. The cabane struts are pre-drilled at the fuselage end and fit well, but they are left undrilled at the centre section end.

What seemed like hours were spent with plumb line, incidence gauge and digital angle gauge to set the centre section incidence at 3.5deg and the top wings in line with the bottom wings in plan and elevation before finding out that somewhere between building the centre section framework pinned and clamped to the building board, and the finished item sheeted in 1/16 balsa, I had managed to introduce a 1deg difference in incidence between the two sides. Once sheeted it is really rigid, so no chance of steaming and twisting and no alternative but to strip off the sheeting, clamp the frame straight and re-sheet.

 

 

 

 

After cleaning the frame up I used the cabane fixing blind nuts to fix the frame to two accurately drilled lengths of hefty aluminium angle to hold it straight while I re-sheeted it.

 

 

 

All re-done and spot on straight this time. Another lengthy session triple checking the alignment on the struts (easier now the two sides matched) and a nervy half hour marking and drilling the struts and another milestone reached.

 

Then there was a diversion to add some diagonal bracing to the fuselage as I wasn't happy with how floppy it was in twisting and I didn't want to rely on the Solartex to stiffen it up sufficiently. Much happier now, it's really quite rigid and has added little weight.

 

Back to the wings and next job was the interplane struts. I had read warnings that the strut lengths on the plan were not correct, so I made carboard ones first to check. Turned out that the plan ones were about almost 20mm too short, so exact size cardboard templates were made. Quite tricky as the struts not only angle fore and aft, but inboard to outboard too. The supplied steel mounting brackets have to be cut to length, drilled out to suit the mounting bolts (6BA supplied but may change these to 3mm) and the ends angled to match the strut direction. Need to be careful to make left and right handed sets.

 

The cardboard templates were used to cut the 20mmx6mm struts which again needs a lot of concentration to allow for the angled ends in two planes and to make left and right handed sets. All done first time with no scrap, so really pleased.

 

 

 

 

 

All fit nicely and all incidences check out correctly, so very happy. Lots of shaping and sanding of the struts and wings now, then glassing of the centre section and Solartexing of the wings. The struts will need some fine adjustment to allow for the covering and the brackets will also be epoxied in place after covering.

 

Very happy with how it's going now, just need to work out the radio install before covering and sheeting the fuselage as the only access after that will be through the cockpits. Bit difficult to put access hatches in a fabric covered fuselage.

 

 

[Danny Fenton]

looking great David!

[Ace]

Lovely craftsman's ship - almost a same to cover it up. 

[David P Williams]

Thanks chaps. As you know, it looks WAY better in the photos than in real life.

 

Lots of shaping, sanding and smoothing today on the tail components and ailerons, followed by the start the relaxing phase of covering. Using up offcuts of Solartex on these small parts - luckily I bought two 10m rolls when they were selling off stock after stopping production. The instructions say I will need 10m for the wings and tail and 2m for the fuselage.

 

Ordered scale rib tapes from Mick Reeves. I'm only doing the top surfaces and probably only the wings and tail, not the fuselage. Even so, at 300mm per wing rib, that's 50 metres of rib tape and about 2500 dummy stitches.

 

Started with the rudder -

 

[i12fly]

Lovely build! I've only seen one fly but it was very tail heavy (like many Flair?), it was lucky to arrive back in one piece. There are quite a few forumites here who can advise if the plan CoG is correct with model horizontal or pointing down.

[David P Williams]

The engine I'm using is more than twice as heavy as the kit recommended one, so I'm hoping that will help with the tail heavyness. I'm sure I'll be back for advice on CofG before I commit aviation with it.

[David P Williams]

Well, another six months has gone by with little work on the Stearman. I must be heading for a longest build prize. I had a big loss of confidence in my ability to complete this to a good standard and even contemplated selling it as a project, but I've given myself a stern talking to and now I'm trying to devote some serious time and effort to it in order to have it ready for outdoor spraying when the weather improves, and ready for flying this summer.

 

So - here's where I'm up to. I needed to paint the cockpit interiors while I still had relatively easy access before covering and panelling. I also needed to work out and fit cockpit flooring to cover up the radio kit and batteries etc., instrument panels, pilot's seats and of course pilot figure or figures. All of this was easier before covering as I can get fingers between longerons and also see and measure from all round. There has been much headscratching and not much actual doing, but I'm finally making progress.

 

 

Usual use of cereal packet to work out size and shape of seat.

 

 

Panels based on instrument sets from Aerocockpit, but instrument faces replaced with slightly more accurate 1930's US ones - mph and feet not knots or meters.

 

 

The Stearman is probably going to be finished as a US Navy N2S, so trying to find suitable pilot figures was difficult. They either look cartoonish, or British, or £120 each. I found some beautifully sculpted figures for 3D printing via Thingiverse. They are not free downloads, they are commercial offerings from Max Grueter and cost me $39 for the files. As supplied they are 1/6 scale, but are easily scaled in Cura when loading for slicing. Although the Stearman is referred to as 1/4 scale it is in fact 1/4.3, so after wrestling with the maths I needed to scale them up by 139.5%.

Of course that meant that the main body component was too large to fit on the bed of my rattly old Anet A8 3D printer, and anyway it looked like a 2 day print and I don't like leaving the printer running unattended for long periods.

Forunately, when my copy of Fusion360 upgraded itself to the latest version, it now includes some pretty good mesh editing facilities, so I was able to divide the main body into four components initially, then six to keep the print times down. I now have right and left pilot's arms, right and left gunner's arms (these may work for the instructor figure), right and left torso, right and left thighs, right and left knees and goggled and open face heads. They should all glue together OK. Still experimenting with Cura settings, but so far I have these.

Not looking forward to the painting stage.

 

 

I also cheated by buying seatbelts from Aerocockpit rather than messing making them from tape and lithoplate.

 

 

The finale time consuming job has been sorting out the vac formed wheel hub covers. These didn't fit the supplied wheels, so I ended up turning spacer rings to look like aluminium wheel hubs (you can just see them in the pic) that had the correct sized recess for the hub covers.

 

 

My intention is to not have switches but to remove one or both floor panel/seat/pilot units to directly plug or unplug flight and onboard glow batteries and also to remove the batteries for charging. Trying to work out if this will work by measuring with bits of wood and string is hopeless, so next steps are finishing at least one pilot figure to finalise the seat size and shape and making sure that when fitted to the removable floor panels that can still be fitted and removed without fouling anything.

After all that I can move on to covering.

[Harrier Mate]

David,

sorry I’m late joining your thread. I too have a flair Stearman which is ‘framework’ complete and was about to install a Saito 180 which matches the 6 dummy cylinders perfectly. But I’ve now been bitten by the real radial bug and am toying with installing the UMS 7 -90 gas radial but I’m frightened by the huge extra weight, prop length and excess power output. 
Have you finished yours yet??? How well does it balance with the extra weight up front?

Sorry for all the questions but I’m new to radials (and gas power rather than glow)…. And it’s expensive albeit beautifully scale size for the front of the model!

[David P Williams]

Hi HM, so sorry I missed your post, I've been away. I was just like you - when I originally obtained the kit many years ago I was going to go the Saito 180 route and even bought one in anticipation. for many reasons it was over 15 years before I started to build the model and by then, like you, I had been seduced by the almost perfect scale size of the UMS 7-77 or 7-90. I don't have any petrol engines, I'm quite happy with glow, and the extra fuel cost makes little difference with the small amount I use in a year.

Anyway, I'm sorry to report that a combination of personal and practical changes in circumstance meant that it was unlikely I would be able to continue with this model and I sold it as a project, just after the Cosford show, to one of the display pilots there. I'm sure that he will complete it.

Sorry I can't be more help.

David