Sopwith Batboat

[g_kandylakis]

It was back in 2004 when I first discovered Small Flying Arts. Then I was building my Sopwith Batboat in 1/20 scale, as a CO2 powered free flight model, for the coming Interscale competition in England.

The model was a flop as a flyer and got converted to electric RC woth the coming of small light RC systems a few years later.

As such it flew well enough for many years, even being somewhat underpowered. It had already suffered some damage during free flight attempts. Additional research and documentation over the years revealed a number of scale accuracy issues as well, so eventually the thought of rebuilding it became firmly stuck in my head.

Now, 20+ years later, I am building it again. The rebuild started a few years ago and was documented in the original HPA forum, but all that is gone now.
So I intend to continue from there and perhaps revisit the older posts and pictures, when time permits.

[g_kandylakis]

to paraphrase the famous disco song: "You should be building, yeah"...

The Batboat is my current project and has come at a stop in recent days, due to understandable reasons 

Current status, more or less as it was a couple of months ago. Started with covering, did the two rudders and an aileron.

Currently rather cold to continue (I ventilate as I use dope and thinners for covering) so it will have to wait for a bit later

Plenty of other things to do though, currently working on the dummy Green engine.

The old one from 2004 was almost exclusively made out of balsa. This time, because of the same bad habit I inherited from Mike M. there is plenty of polystyrene externally. Very thin though and the balsa base is hollowed out as much as possible to reduce weight

[g_kandylakis]

Close up on the motor base made of plywood.

The motor is fixed to a basswood beam, secured with the larger screw.

The beam is inserted into the plywood base and has 4 screws at the front, for thrust adjustment, up-down and right-left, about 3 degrees in either direction.

Being a pusher  I hope it does not need a lot of additional fixing.

The top of the dummy engine is removable to allwo more access.

The BL motor wires go down to the hull along the rear right motor mount strut

[Steve85]

What lovely models.  I'm fascinated by your adjustable motor mount and may just steal some of the ideas behind it...

The sub-forum description states "small" scale RC models... at the risk of starting a legal-speak argument, how "small" is "small"?  I'm about to start building an own-design 1/12 scale Fairey Swordfish (about 45") - does that count as "small"?

Steve

[g_kandylakis]

Hi Steve,

I sent you a PM after you posted. Did you get it or did you miss it?

George

[g_kandylakis]

Parallel to the forum, some aeromodelling needs to be done as well...

My aim is to have the model finished and flown by April. But I also need a proper documentation drawing, which I am in the process of finishing. Next step is to have it validated, to be acceptable for contest use.

So, more PC time for now.

But I am close to finishing it. Here is the (almost) finished side view of the Batboat.

[Squirrelnet]

Great build thread George. The adjustable motor beam is a brilliant idea. Like Steve I maybe pinching that at some point ... (I have a CO2 Supermarine Walrus idea I want to do again at some point and that would solve few issues)

Look forward to seeing the rest of the build when you get a chance, as you say, forum aside aeromodelling is why we are all here 

[OZPAF]

Always enjoy your approach George, to both duplicating the structure while keeping it light and your ingenious engineering solutions.

I hope you are able to enjoy some more building time.

John

[dputt7]

Hi George,
           Always liked this model and it is great to see it being built again. Could you tell me the thrust angle of the motor and does the model need up elevator as you apply power. I have a Free Flight model with a similar layout and could use some advice on thrust lines.
                                                  Thanks, Dave

[g_kandylakis]

Hi Dave,

The motor in my first one was set at 0 degrees. I never went through the trouble of adjusting the thrust angles, it was not easy to do afterwards inside the dummy engine.

Yes, it did require up elevator, as a matter of fact, I added some mix of throttle to elevator. It did not help that the model was somewhat nose heavy too, but I had little place in the rear to conceal any ballast. So (wrong) I used up elevator more that I should.

With the new one I hope for improvements.
The weight distribution should be better, I moved the RC components as far to the rear as I could. They are still located in front of the CG, but less so.

The battery too.

And the ability to add some downthrust should help too.

We'll see...

Side view drawing finished, now to finish the top view.

George

[g_kandylakis]

So, yes, I split the messages on thrust settings for pushers, they deserve their own thread in the Model Aerodynamics board.

Not much new to report on the Batboat for now, except for a very important step.

I finished the drawings and after some adjustments and corrections I got them validated too (thanks to BMFA, Rich and of course Mike), so I can proceed with the building without worrying about changes in the future.

Covering can be resumed now...

[g_kandylakis]

At last, some progress.

Started covering on thw wing panels.

I am using pre-shrunk white esaki, shiny side out.

Bottom side done first, with the wing sitting on a base, to keep it parallel (forgot to take a picture of this, will do.

Thinner brushed through the tissue, tissue pressed evenly during drying using a piece of balsa.

[g_kandylakis]

The wing tip segment is done with a separate piece of tissue, due to the doble curvature there.

Trimming the edges for overlapping around the wingtip.

[g_kandylakis]

and last for now, although it preceeds covering, the pre-shrinking.

Some more tissue pieces are needed, so more are getting pre-shrunk.

Tissue glued on with UHU stick glue. Then full wet with water, left to dry.

cut from frame and ready to use.

[g_kandylakis]

First picture for a friend... The result of pre-shrinking. Every wrinkle dissappears. even the fold lines.

The base for covering of the bottom wing side. Stabilises the flimsy structure and ensures it is "parallel" during and after covering.

When the bottom side is done, the top is much easier as the wing sits properly flat.