TRIALS AND TRIBULATIONS

Well hello all,

This is really a tale of rush to see if it works syndrome - been building a near enough scale of Bluebird, powered by a EDF fan. along the lines of Ashley's model of bluebird as he was my inspiration.

To cut a long story short I was impatient to see if the actual model worked. On paper it would work - because I was using a fan which was rated at 7.5 lb thrust at 22 volts. The model all up with batteries and that - only weighed up at about 5 lb . That is a good ratio. So, this morning I took it down for sea trials - minus the intake spray defectors and also the sponson spray defectors. Just a single rudder on the stern, no stabiliser.

Model did move prettry briskly at first across the water. She failed to achieve the plain. Anyway, after my Co-Pilot (my son) indicated she was sucking in gallons of water through the air intakes and literally filled the boat with water and it was briskly brought to shore.

We panicked as we tried to salvage the electronics - but you know what - it all survived up to now. Sadly , no pictures of her on the water , but they will follow when we do further sea trials and completed the model

Here are a couple of pictures of her now with me fitting the spray defectors this morning.

John

I have to say John she looks beautifully built. The important thing is that you got her back and learned a lot!

Hi John,

My experience of flying with the new generation brushless fans is your fan probably can't breath with the scale intake area, we have to cut cheat holes under the aeroplane, not appropriate on a boat !! what you have is a frustrated hoover which would explain the ingress of water ? If with extra thrust and speed she should lift higher and stay dryer ? Many moons ago I designed Wetjet which was a free plan in Model boats I learned that weight is your biggest enemy and I were building it again I would use Depron glass clothed to save weight ! I did the same as you with a planked eflux tube which we now use rolled acetate , I think the sponsons is the right way to go as the wetted area is greatly reduced once you have the speed

Regards Ray

Hi John

This is Wetjet which had an old school Womotec fan with a brushed 480 which didn't really go like I'd hoped but with a brushless fan and Lipos it may be much better ? I'm almost tempted to have a go

Regards Ray

Hi there Richard and Ray

Yes, I have spent this afternoon re-checking the electronics making sure that they are working okay, not that there is much inside - just one speed controller, one servo and the fan. Ive been drying the internals out with the hairdryer gently and a low heat. Everything seems to be okay. (Touch wood - up to now)

Also, I have been making & fitting the spray defectors which sit either side of the intakes as on the original K7 Bluebird. Apparently the original Bluebird suffered the same fate (swamping of the jet engine).

Also, tomorrow, will be fitting the 3 spray defectors which fit directly underneath the slope on the bow of the boat. I am thinking of making them from light aluminium.

To answer Ray's queries - I am unsure if you noticed but the canopy is made from aluminium mesh and underneath the canopy there is a ducting straight through to the fan. Either side of the canopy there are cheat holes as you call them to allow extra air into the fan. Also, the overall dimension of the intake is slightly larger than the scale size.

I have been looking to see if I may be able to re-position the batteries - At the moment I have them side by side, roughly just behind the front plaining shoes of the sponsons . I would like to get them in line, but, I have get one battery underneath the fan which may be an impossible task.

The other thing I note was when we did the trials this morning - I decided to run the model on 14.8 volts keeping the 22 volt batteries in reserve - as I was totally unsure how the model would perform. The one thing I did learn was the characteristics of it for steering was terrible - even though the rudder is slightly larger than scale.

I am looking forward to my next trip down to the lake - but I might wait until next Sunday when the lads are about with their waders.

On Saturday I was testing the rudder servo and I had a 7.4 battery connected up just so I could check the centralisation of the servo - as the speed controller has the BEC built in to power the receiver. Devilment took over and I thought to myself go on give the fan motor a blip to see what it's like - what happened - I don't know if you noticed - the set of drawers on the wall behind the boat - 5 or 6 drawers flew out spilling all the components onto the floor and I spent a good bit of time finding them and retrieving them - note to myself - do not do that again.

John

Edited By John W E on 27/08/2023 18:46:50

Well, I have spent the whole week modifying and adding spray defectors, either sides of the intakes. I also (on the inside of the sponsons & on the main slope of the Bow) - fitted the defectors were fitted. So, used freshly charged batteries - and went down to the Lake this morning. First set of batteries used were 14.8 volt and these were made up from from 5200 mAh at 7.4

She came up on the plane no problem. Couple of trials runs and pretty happy with that run.

Brought her in and made sure there was no water inside. We then swapped over to the 22.2 volt batteries - and they are also 5200 mAh batteries at 11.1 each.

All I can say - WE NEED A BIGGER LAKE -

What bothered me was (and it did take some getting used too) was you shut the power off and she still runs on at a considerable speed for a good distance.

I am, going to try and download the videos which my co-pilot son took

Here are a couple of still pictures - I am well pleased.

Edited By John W E on 03/09/2023 12:24:07

Looks superb John, a credit to you.

Edited By Colin Bishop on 03/09/2023 17:16:13

WOW, and the (live) swan didn't seem to bat an eyelid. Looking forward to more video runs. Well done.

George

Edited By gecon on 03/09/2023 18:08:26