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Jan 10, 2013, 05:39 AM
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Trevorh, if your model weight is below 5.5 lbs, then reducing the width by 1 should be fine. Do not reduce the depth or shape of the bottom of the floats.
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Jan 14, 2013, 07:07 AM
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Trevorh's Avatar

Fuselage top and cockpit

The bottle canopy turned out to be very rigid. This will be good news when the model is upside down in the model stand but it does mean that there is little or no scope for flexing it to fit the fuselage. As a result, building up the surrounding structure around the base of the fin has been a lengthy trial and error exercise and the fit is still far from perfect. I think the general effect is okay though so will now move on to the next stage - just as soon as I have decided what that is!
Jan 14, 2013, 12:00 PM
Student of Ivan
mountainman2442's Avatar
I really like to look of the canopy Trevor. The plane takes on a more "scale" appearance with it. Nice job.

Jan 16, 2013, 04:53 AM
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Trevorh's Avatar
Couldn't resist putting it together again, on the pretext of doing another weight/balance check, but really just through indecision about where to go next with the build.

Nevertheless, a couple of decisions have been taken:
i) The tailplane is now screwed on (wood screws into 1/4in dowel inserts) but will be screwed and glued after covering.

ii) The all up weight still looks like coming in at 5lb or just under so motor has been ordered - EMP N5045/09, 600kv, 195g.

The balance exercise showed that, with a 4s x 3000mah LiPo pack, the nose will probably need to be extended slightly to balance without lead. However, I'll wait until I can run a test with the motor to decide whether to run off 4s or 5s, the deciding factor will be prop size - I reckon anything over 13in could be getting a bit close to the water once the tail comes up.
Jan 29, 2013, 11:35 AM
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Trevorh's Avatar


After all the work on the tail and turtle deck, I had a fair few offcuts of 1/16in balsa laying around, so embarked on some rib cap stripping - hardly the most exciting or photogenic part of a build, but it had to be done.

The underside leading edge wing fairing is also now roughly fitted - final fitting will have to await completion of the front end of the fuselage, which awaits finalisation of the firewall position, which awaits a motor test, which awaits some weather where I can venture outside without sinking into the mud, getting frozen to death or blown away. The joys of the English Winter!

Meanwhile, I have made a start on the winglets. These are to the outline and section shown on the plan, but the construction is modified to my preferences. Just as well really, since there are a fair few errors on the plan, even in such a small simple structure as this. Shame really - Laddie's design deserves better but, as I've mentioned earlier, it looks as if the publishers just commissioned the drawing of a built-up option for the wing and didn't check it with a prototype build.

Anyway, after adjusting for a few mis-drawn ribs, the panels have gone together pretty well so far, and now I am tackling the 3D geometry puzzle of fitting dihedral braces. Watch this space!
Jan 29, 2013, 01:46 PM
What could possibly go wrong?
nickchud's Avatar

This is going to be a lovely plane!

Jan 31, 2013, 04:38 PM
Registered User
Trevorh's Avatar
I'm still working on the tip panels but today it was time to assemble it all for the end of month photo call.

All up weight still looks on target for about 4lb 8oz.
Jan 31, 2013, 05:15 PM
Slip the surly bonds...
Sopwith Mike's Avatar
With any luck, the February photo-call should be ready to fly. She looks great, what a mixture of shapes - and what an inspired designer!
Jan 31, 2013, 07:22 PM
Registered User
wijwoj's Avatar
Looks stunning Trevor. A credit to Laddie's design!
Feb 01, 2013, 06:46 AM
Trevor, a most impressive build! I might suggest you consider material from a plastic folder used to protect office or school reports to protect the fuselage bottom at the rear, of even the forward portions of the floats. They are available for a $1 or so here and come in various styles. I prefer the ones with slightly thicker material, clear front and colored back portion. I cut sections to size as needed, then attach them with a water resistant contact cement (3M 77 Spray, or equiv.). I have used this "protector" plastic on several planes, land and water types; covered and painted balsa, fiberglass and depron surfaces. It is tough and fairly light.

Perhaps the most notable example is a 150% sized "Polaris"; Steve Shumate's design based on Laddie's 'Northstar', constructed of depron foam. My plane's flying weight is a bit over a 1.3 kilograms (42 oz). I mounted the folder plastic on the fuselage bottom and bottom of the tip floats. As well as flying from the lake, I rather often perform takeoffs, landings and touch-n-go's on gravelly and paved surfaces without nicking or denting the depron.

Feb 01, 2013, 07:09 AM
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Trevorh's Avatar
Hello Tony. Thanks for that. I must admit that I'd never thought of using plastic film in that way. We used to put carpet tape on the undersides of our slope soarers to protect them from gravel rash, but I don't imagine that would last long in an aquatic environment!

For the floats, I had wondered about adding a layer of 1/64 ply along the bottom to protect them from damage, but this would be before covering so wouldn't protect the finish in the same way as the film would.

The tailskid question is not so much about protecting the finish though - more about saving the rudder hinges from taking any weight when the model is set down on the ground. This would become more important if I ever flew the Aquabird from grass, when the rudder could take quite a knock on landing.
Feb 01, 2013, 08:05 AM
Registered User
The model is looking good. As for protecting the tail when flying from grass. On the original Aquabird, I had wheels on inside of the sponsons and the tail wheel as shown in post #42.Later on I only had the skid as shown in post #44 and no wheels.
Feb 01, 2013, 12:45 PM
eye4wings's Avatar
My simple and cheap solution (since it is made from a material readily to hand) would be bend about 3" of 20 swg wire into a semi-circle and glue the ends into the underside just ahead of the rudder.

(That was thoroughly predictable then, wasn't it?!)
Feb 02, 2013, 07:00 AM
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Trevorh's Avatar

Motor Test

I finally got outside to run up the motor. It is an EMP N5045/09, 600kv and a 13 x 10 APCe prop was fitted for the test.

First run was with a cheap Zippy 4s x 3000mah pack and the current went up to 32amps then immediately sank back to 28amps. Swapping to a newer Gens Ace 4s x 3300mah pack recorded a steady 46amps for 7,500rpm.

The on-load voltage wasn't measured, but this must equate to about 650W which, with an AUW of under 5lb, should be enough. On this basis, I will try to balance the model for 4 cell operation, with the option of going to 5 cells and a 12in prop if prop/water clearance is an issue.
Feb 05, 2013, 11:50 AM
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Trevorh's Avatar

Sponson construction

Now that the wingtips are permanently fixed, work has started on the sponsons. As Laddie suggested, I have narrowed the sponsons in line with the expected weight reduction compared with the i.c. prototype.

I over-ordered on 3/32in quarter grain balsa for wing ribs, not realising just how much wood Robin's 'strip rib' technique would save me. Also, for reasons that I don't understand, I seem to have under-ordered on 1/8in sheet. So, the sponson sides are made from 3/32in quarter grain, which I have to say, looks and feels ideal for the job.

The triangular stock took a lot of notching to go around those curves and will need to be notched again before the fronts of the sponsons are pulled in. As always, the fit to the wing took a fair bit of fettling but I'm quite happy with the fit so far.

I'm planning to glue the sides and the one former to the wing and build the rest of the sponsons in situ.

After that, there's more or less just the nose to go. . . . . .

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