Ekranoplan

[ashley needhamParticipant @ashleyneedham69188]

Jeremy. Nice, better than mine, should be nice and smooth.

 

I used p38 car filler to provide a smooth fillet to blend the wing into the body. You may want to consider something else as your wings are going to be very soft (or you could eze/fibreglass them first)…I might suggest for the shoulders (fillet), you butt the inner edge up to a block of foam, draw around it to get a profile and cut a thin wedged shape out to glue over the wing/body joint and sand this to shape.

 

Optimum location !! I looked at it, weighed up the pro`s and cons of getting it wrong and stuck `em on !! The leading edge is 30mm avove the bottom of the hull, and the trailing 22mm.

 

Before sticking anything on, balance the boat in the bath, with all the gear inside or on top (or a guestimate in materials for the weight of bits not yet made), and mark the waterline. Dont forget the boat sits, or will need to sit, well back, and not level, as the rear will lifts by a good15-20mm when power is applied, as a guide.

 

 

Then when you hold one wing in position you can see how close to the water you might risk it! I think I probably overdid the incidence, looking at all my pictures, as the leading edge is some way clear of the water in virtually all the shots and a rise of 25mm may be ok at the front.In actual fact a small rise at the rear may be benificial, to flatten the angle off a bit and have the training edge clear of the water. I would leave lots of material on the end plates/floats and have a go with them large..you can sand down easily enough at the pond side, and if you take just a bit too much off, its easy to simply glue a bit back on. I made mine deep to start with after experiences with the Sunderland etc, but probly wide is the way to go, no one will notice extra wide floats. Mine are 20mm wide at the bottom and about 35mm deep in the centre, tapering to a point at the front and flattening off to about 30mm at the rear.

I sanded the bottoms of these very slightly outwards rather than flat to tend to clear water outwards and not inwards if you see what I mean. At speed they are sort of foils rather than just floats.

 

I couldnt think of a way to trail the wing position without building virtually two boats( I thought of using hot glue as a temporary measure, but if one wing fell off…), so I went for safety. This was also one of those things…the real craft had the wings at the bottom of the hull, I felt that this was a non-starter for a model and so moved them up as little as I thought I could get away with, with regard to aesthetics and operational neccessity.

 

Its very tricky trying to double guess what will happen to an experimental craft once water and boat meet. The Sunderland was a case in point, the humungous nose down attitude it developed when power was applied made my heart sink, after all that work. BUT with a bit of perseverence !

 

Ashley

 

[JeremyParticipant @jeremy15845]

Ashley

 

Thanks for your quick reply and as always helpful advice. I plan to fibreglass the body, wings and tail plane separately before attaching anything. The body anyway needs to be fully waterproofed before a bath test. I like the idea of finalising the shape of the floats during initial trials. I note the point that they can act in part as foils.

 

I found Shorty in your album together with two other flying boats. Have you ever been tempted to get any of them airborne, even if only for a few metres?

 

Happy Christmas!

 

Jeremy

[ashley needhamParticipant @ashleyneedham69188]

Jeremy. It would be nice, I confess, so seeing the flying boats hop off the water..but this requires substantial power. the engines on shorty cost about £2 each or something and a set of 4 props was 88p…..the economics speak for themselves !!

 

In the case of the Sunderland, i think that larger props would then be needed and spoil the look at the size its built at. The other boats were for my son, the stripy one in fact being not built as a radio control item at all but something simply to put soldiers on.

 

INCIDENTALLY, the hull of that one was made as a test-hull for the Ecranoplan to see if that size of hull would support all the bits and bobs and make it a viable project!

 

Making the Ecranoplan wings a bit more horizontal would allow “the hop” to become more controlled when using an 11v LiPo…

 

Ashley

[ashley needhamParticipant @ashleyneedham69188]

The build feature for Shorty the Sunderland can be found on the “features” page under builds, about page 5.

 

I tell you what, If I had found the little Park brushless motors when I was building Shorty …..

 

(but..£30 a piece x4 as against I think £1.85 x4 for the others…..hmmmm)

 

I splashed out on the German flying boat and used 2x speed 280`s !!!

 

Motors for the BFB3 stripy one came from discarded cheap battery toys from a few Christmases ago, although I did change the centre one later on to an ordinary MFA 280 motor for more power to improve the steering, as only the centre prop washes over the tail rudder.

 

Ashley…….no expense spared, me

[JeremyParticipant @jeremy15845]

Ashley

 

I’ve found and read the build feature on Shorty. Interesting that it was powered by a water propellor. I was thinking about that for the Ekranoplan. No trimming problems caused by the tail lifting under power and it would definitely get up on the plane. My Bluebird K7 is three times the weight and, even without Lipos, goes at a fair lick with no prop in sight!

 

 

Dependent upon how the A90 goes with the air prop, it could be a modification for version 2. There would be plenty of space in the hull.

 

I got the Eze-Kote and fibre glass earlier today so I can move onto the next stage of construction.

 

Jeremy

[ashley needhamParticipant @ashleyneedham69188]

As the A90 has an air prop, it seemed to me that it should be powered by it and not a cheaty water prop! Besides the room is there for something powerful and having a decent prop size. If fitting a water prop to the A90 I think you would have to dump the lift off the wings otherwise it would just porpoise up and down as the drive came and went.

 

It will not be as fast as the Bluebird, I have to say looking at the pictures.

 

The Sunderland was of course only going to be a boat and so the use of air props was not considered when I started the build

 

The Bluebird looks great.. which motor (and Kv) did you use and how many volts?

 

Ashley

[JeremyParticipant @jeremy15845]

Version 2 on indefinite hold, maybe not such a good idea! Anyway, I still have a long way to go on version 1.

 

Bluebird motor is a BL2 from Prestwich Model Boats, a 2845 with 2881KV. Battery is an 8.4V NiMh pack. A friend whose build I followed has since moved on to Lipo power which, still with the same motor, makes it considerably faster.

 

Jeremy

[ashley needhamParticipant @ashleyneedham69188]

Chaps, for those even remotely interested, have posted video clips of the Ecranoplan on Youtube…. search for my channel under “bandleader42”.

 

Not me driving unfortunately. For me its quite quick enough, and in any case you really need a reference against another boat to judge just how fast it is going.

 

Not only that but the band is also available for bookings……

 

Ashley Happy noo year and all that

 

[Bob Abell 2Participant @bobabell2]

Hello Ashley

As a keyboard player myself, I admire your dance band involvement.
Well done, the band!

Seen your flying thingy….Very pretty, but would like to have seen your model on the point of taking off!

Happy New Year my M8

All the best

Bob

[ashley needhamParticipant @ashleyneedham69188]

Jeremy. `Plan coming on now! gives me a bit of deja-vu looking at your build pictures.

 

Be in a position for a test flight soon once the wing ends are fixed on? or do you have a prop yet?

 

Ashley

[JeremyParticipant @jeremy15845]

Ashley

 

Floats now added; one still to be fibreglassed. I adjusted the angle of incidence of the wings in the direction you suggested in earlier posts. Trailing edge to the base of the hull 25mm instead of 22mm; for the leading edge 28mm instead of 30mm. Floats about 22mm wide at the bottom, tapering out towards the front. The bottoms of the floats are at the same level as the hull. Whilst the wings are epoxied in place, I could still prise them off the hull if needed (I did not glue the full surface area). Changing the floats would be more difficult but I could make new ones. I still have to source a propellor. I would want at least to primer coat the whole craft before an intial test.

 

I watched your video clips and was surprised how sensitive the craft was to movements of the air rudder. It will be interesting to see how the water rudder compares.

 

 

 

By the way, your last two posts on this thread have been duplicated. Is your computer set to send things twice?

Jeremy

[ashley needhamParticipant @ashleyneedham69188]

jeremy, Computer slow, operator too fast with the “post” button.

 

I dont suppose you will have to change the floats.

 

Are you having the rear fin rudder “self castoring” so it can wag? or will it be fixed, possibly after tests!

 

Ashley

[JeremyParticipant @jeremy15845]

Ashley

 

Rudder hinged with strips of thin plasticard, so “self castoring” to an extent, although with some resistance from the plastic. It could easily be fixed.

 

Jeremy

[JeremyParticipant @jeremy15845]

Ashley

 

Construction complete except for fairing in the wings. Two props bought – 5.7×3 and 5.5×4.5. the 5.7 has just enough clearance; I imagine that the 5.5 with the sharper pitch will be more powerful assuming the motor has enough oomph. I couldn’t find a 5.5×3

 

I noted that you used Humbrol tinlets for painting the top coat. Were they the acrylic or the enamel versions? Did you airbrush or brush them on and did you use thinners? They would seem to be small tinlets for covering a larger area and presumably not easy to airbush camoflage stripes.

 

I need to modify the right hand stick of my Planet T5 transmitter to ratchet action – centre springing would leave the motor turning at 50% as there is no reverse on the ESC.

 

Jeremy

[ashley needhamParticipant @ashleyneedham69188]

J. Ordinary enamel Humbrol. Tinlets fine for painting everything, its suprising how much area one tinlet will cover!! Brushed them on with a flat brush, about 12mm wide from an art shop.

 

My floats, although its not so obvious from the photos of it finished (they started life being very large) are quite a bit thinner and sharper at the front compared to what you have there…but I would leave them as they are to start with and take a block and sandpaper to the pond and see what you can get away with.

 

I wouldnt like to say about the props, The smaller pitchier ones I had were not as good as the 5.5×3 ?? I would imagine that the 5.7×3 will perform as well as if not a touch better than the 5.5×3?? and the 5.5×4.5 ??? who knows!! be interesting to hear what you think is better.. I may pop out and buy something the same if there is a marked difference. I would also try an ammeter on the setup to see what the varioyus props draw..the battery is supposedly only good for about 8A I think according to the website (component shop).

 

Just thinking about the tail rudder, this might have a strong effect on the steering at speed, so would take some tape along in case you need to immobilise it when you give it a trial.

 

Ashley…..exiting, almost there!!

[JeremyParticipant @jeremy15845]

Ashley

 

Where can I get an ammeter which would measure up to say 60 amp DC – probably the max I would need for model boats? My Maplin multimeter has a limit of 10 amp as do the many others I have found on the net. There are clamp on units which measure higher amperage but I would prefer a digital read-out unit with leads. I have looked long and hard but to no avail! What am I missing? Am I confusing amps with milliamps?

 

Jeremy

[Gareth JonesParticipant @garethjones79649]

Jeremy,

 

Rather than buy an ammeter which would only allow you to measure the motor current, you would be much better looking for a wattmeter. There are lots of them around especially used by the model flying fraternity. Prices are typically £20 upwards and they usually measure voltage, current, power and energy through the meter, all at the same time. The more expensive versions will record data as well. I have made up a set of adapter leads with various connector combinations so that I can connect between the battery and speed controller of all my boats (and other club members) and its very easy to see how much power a motor is taking with the propeller in and out of the eater.

 

Gareth

[JeremyParticipant @jeremy15845]

Gareth

 

Thanks. It certainly helps to know what you are looking for! I’ve gone for the one at the link below. HobbyKing had several others but all out of stock.

 

http://www.focalprice.com/YOE03B/100A_Multifunction_Watt_Meter_Black.html?Currency=GBP

 

Jeremy

[ashley needhamParticipant @ashleyneedham69188]

Good job Gareth replied as I cant remember where I got mine from !! it is only a cheap

30-0-30 plastic job, looks a bit like a car or old motorbike ammeter.

 

Not particularly accurate I dare say but it gives you a rough idea as to how much you are drawing, just in case..

 

Ashley

[JeremyParticipant @jeremy15845]

A90 now complete. Looks OK but unfortunately too heavy. Including the battery, it weighs in at 800g compared to Ashley’s original at 660g. This is only partly explained by the fact that the body is 5mm wider than Ashley’s to accomodate the battery lying flat.

Floating in our garden pond, the trailing edges of the wings touch the water.

So what to do now? I think I have two options:

 

1. Stick with the current NiMH cell and reduce the weight by replacing the 35amp ESC with a 12amp ESC (saving 23g), replacing the mini servo with a micro server (saving 8g), replacing the heavy wires connecting the ESC to the motor with much lighter wires (saving ~ 16g) and finally removing the expanded polystyrene stuffed in the front of the fuselage, put there to help keep A90 afloat in the event of disaster (saving ?). Without major surgery to the craft itself, it will be difficult to reduce the weight below 750g and this may still not be enough.

 

On the question of connecting wires, I worked on the basis of using much the same gauge as on the input side of the ESC. Given that the wires attched to the motor are very thin, was this overkill?

 

2. The second option would be to go with a Lipo battery and here I would appreciate advice. The Park EFLM1010 motor requires 2-3 Lipo cells. Its continuous current requirement is 7A and max burst current 11A. Looking at the Vapextech website, I could go right down to a 7.4V Li-poly (3 cells?), 900 MAH with a 19Amp continuous rating and a 38A burst rating. Weight 48g which would reduce the craft’s overall weigh to 628g, below the weight of Ashley’s model. A 1650MAH battery with a 36A continuous rating and 72A burst rating weighs 88g which would still keep the overall weight close to the target.

 

On the face of it, there is a considerable mismatch between the continous and bust current specs of the motor and those of the batteries. Does this matter or are there Lipos with specs more closely aligned to the motor? If I went with one of these Lipos, would I need to upgrade the ESC? I have a multi-function watt meter on order so I will be able to measure current and mange the performance of a Lipo battery.

 

I note that Ashley thought about using an 11.1V Lipo but, if I understand correctly, this would have four cells, more than the maximum specified for this motor.

 

As you will see if you have been kind enough to plough through the above, I am more than somewhat confused!.

[Trevor HollowayParticipant @trevorholloway99134]

Have you tried removing equipment (battery pack, receiver, wiring etc,) to see what weight you need to get down to for it to sit on the water correctly – this would at least give you something to aim for ?

[ashley needhamParticipant @ashleyneedham69188]

Jeremy. Looks great ! Nice colours,

 

Dont worry about the weight. I just re-weighed mine and its showing just over 700G on the scales. How accurate are these scales?? dont know.

 

Wings touching the water at rest.. mine do as well. Have you zoomed across the pond yet? I would not worry and make NO alterations until you have tested it out and tried a few different propellors. You will probably be able to halve or take 2/3 off the wing floats..mine are much slimmer (deep) than that (although they started out at your size initially), however try a run with them at this size first and take some off bit by bit.

 

With regard to LiPo`s. 2 cells is 7.4v and three is 11.1V so you would be able to go to 3 cells no probs. An 11V LiPo would probably be half the weight of the current battery (at a similar capacity) and of course add another 5000 or so rpm!

 

With regard to an ESC, if you know roughly how much the motor is drawing (using your meter) then an ESC of say 10A or so above this should be more than enough. Dont forget that you are not at risk of stalling the motor, like a boat, on weed or something. More likely is the prop adaptor will loosen and the prop come off.. my motor gets only modrately warm after a good thrashing and the ESC only barely warm.

 

11V is taking off and flipping over territory. Could I suppose be tamed by a smaller prop to provide less thrust at max revs compared to the 5×4 or whatever you have.

 

Take it out first, worry later.

 

Ashley

Edited By ashley needham on 26/01/2012 17:46:09

[JeremyParticipant @jeremy15845]

Ashley

 

Thanks for your reassurance and advice. I will give A90 a go as it is and report back. I should get the meter in about a week’s time and I will wait till I get it so I can measure what the motor is drawing.

 

Just one point of clarification. When you refer to slimming the floats, are you reducing the top to bottom dimension (at the moment the bottoms of my floats are level with the bottom of the hull) or the width dimension which I think you said was 20mm? Does this width taper from front to back?

 

Jeremy

[ashley needhamParticipant @ashleyneedham69188]

Jeremy. Yes, the top-bottom measurement. Mine started out level with the bottom of the craft. but now the bottom of the floats is much higher, and the floats are a bit thinner..

 

I tapered mine just a bit so the top looks slimmer at the top but provides a bit of width at the bottom to act as an outrigger or ski for stability when the wings are clear of the water, as no doubt yours will be !!

 

Ashley

[JeremyParticipant @jeremy15845]

Ashley. Thanks for the clarification.

Jeremy

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