Convair YF2Y-1 Sea Dart

[Dave Kellett]

Hi Alex
It's looking fantastic, how close are you now to completion? Do you have any video at all?

Regards

Dave

[Alex Jones]

Hi Dave, The model is finished bar the scale details in the cockpit but we've again put everything on hold due to the pandemic so will finish the testing next year if the situation in Europe allows. We're now focusing on other projects until we feel the situation improves enough to continue... I need to continue updating the thread as I've been side tracked with other work which has taken priority. Unfortunately everything is wrapped up in covers waiting for the spring.

[Alex Jones]

Apologies for not updating this sooner but over the next few weeks we should get to it all finished up to the current state of the model.

With the beaching gear nearly completed we wanted to test fit it to the model to check it was fit for purpose before using it. A few small changes required but it works as designed and is stable even without the lateral supports connected to the rear ski mechanism. Buoyancy will be an issue but we will see how much of a problem it is in the first water test. If necessary we’ll add holes to allow the tubes to flood with the main wheeled section probably requiring a few kilos of weight to be bolted to it.

This is with the beaching gear in the extended position and no lateral support allowing the ski oleos to actuate and the skis retraction to be tested before it goes into the water.

F39B32B2-6920-46CD-9453-3B6FE642EC54 by Alex Jones, on Flickr

D7D7FD2D-B2A2-48AD-8DAF-CA4A42025294 by Alex Jones, on Flickr

A scale model wouldn’t be the same without at least some head scratching.

Photo 30-07-2020, 11 33 21 (1) by Alex Jones, on Flickr

Please note these are not current pictures, the various COVID restriction we now face were not in force when these images were taken.

[Bob Thompson1894]

There was a program on tv about it the other night. It seems vibration of the skis, especially in rough water, was a major problem. Despite that, the pilots loved it.

[Alex Jones]

An interesting aircraft for sure...

I managed to finish the last of the installation on the electrics and engines before doing the first few engine runs. I always get excited seeing a model come alive for the first time. I was working insane hours to get it ready for testing so I didn’t take many pictures, those I have of the final engine installation are below.

36D84025-E839-42B0-AE6A-27D3A30EEF51 by Alex Jones, on Flickr

5F77B2C5-9F79-4B88-A82F-30393F92FDAD by Alex Jones, on Flickr

EFF57CA8-0B8E-4715-9580-837AC4C6AEC2 by Alex Jones, on Flickr

[Alex Jones]

With the model ready for the initial engine runs we took it BMFA Buckminster. Phil and Graham from FighterAces came down to help as it needs three people to safely handle the model. Phil has been with us from the start of this project so I was pleased he got to see it run for the first time, I know its not as interesting as seeing it on the water but it was a big deal for me.

The team at Buckminster were excellent, very friendly and accommodating, I’m looking forward to testing some of our other projects at the site once we’re allowed out again. It was great to finally get to this stage and have everything working, although there is still much to do before it gets wet but at least things are now starting to come alive. The engines ran well after some tweaking with the initial start voltages. I wanted to make sure that the expense of hiring a lake isn’t wasted because we can’t get the engines started so a dry test seemed sensible when running them for the first time in the fuselage.

The beaching gear is shown here in its scale configuration with Phil giving it some scale. The model with the pitot probe attached is nearing 5 meters long so its not the smallest of things.

IMG_4039 by Alex Jones, on Flickr

_DSC7799 by Alex Jones, on Flickr

_DSC7797 by Alex Jones, on Flickr

_DSC7806 by Alex Jones, on Flickr

_DSC7798 by Alex Jones, on Flickr

_DSC7809 by Alex Jones, on Flickr

[maurice northcott]

No superlative good enough ..... just fantastic...... well done and congratulations to everybody involved. Thank you for keeping us advised and showing us progressive photos ......

[Dave Kellett]

Quite simply the BEST OF BRITISH.
To all of the team to reach this stage, congratulations on a fantastic piece of scale engineering.

[Alex Jones]

Thanks guys... I'm not going to be able to put off the flying bit much longer

Phil from Fighteraces sent me a short video he took on his phone, Phil you need to get a better phone! [:)]

https://youtu.be/QhHendC5FDE

After the engine runs it was just a few weeks to go before the first water based tests which was going to be a push. We had to book the lake and flights etc… for the team months in advance and with the lull in the pandemic it was probably going to be our only chance to get some tests in this year. Anything we learn from these could be addressed over the winter ready for further tests when circumstances allow. Unfortunately the tests had to be private as we couldn’t accommodate spectators with the COVID restriction in place at the time.

The model above the waterline isn’t designed to be water tight but it is important that it is splash proof. One of the areas I’ve put off doing for a long time is the cockpit seal as I couldn’t decide on the best way to approach this. In the end we created a 1mm recess around the inside of the canopy and use 1.5mm neoprene rubber with a compression of 40%. This allows the canopy to close then the locking mechanism pulls it down compressing the seal but still keeps the canopy flush to the fuselage. Due to time constraints I couldn’t detail the canopy myself so luckily FightAces managed find time to do the detail work and make the recess. Within a few weeks it was back with me and looking really good. Thanks Fighteraces.

AA77FC63-81DD-485B-8017-5CBBDD639278 by Alex Jones, on Flickr

52EEF8A6-BA10-4801-AFD1-D49CD07B7490 by Alex Jones, on Flickr

The locking mechanism consists of two conical latches that actuate via a servo. These extend into a recess on the front of the canopy and gradually pull the canopy down.

59091FF2-11DD-4195-B7E2-BA6D73815000 by Alex Jones, on Flickr

BCF56C95-CC22-4AFD-B3D3-200428B8E7B3 by Alex Jones, on Flickr

[Alex Jones]

The other area for concern has been the CG, I had been keeping a basic weight and balance sheet incorporating all the components. This had been suggesting we were getting tail heavy and the model seemed in reality to be a little further aft than the calculations. I had failed to account fully for all the wiring that has been required and I was probably out with the weight of the paint. We had always intended to make carbon spars but at the start stopped the process at the aluminium until we knew more about the weight. It was decided now that we needed the spars in carbon to help with the weight and balance so these were constructed using the existing aluminium spars as patterns to making carbon LTM tooling for a full set of carbon spars. It’s worth noting that if this model had been land based we wouldn’t have gone to these extremes with the strength of the wings, fuselage and spars but like the full-size this is more akin to a flying boat. It will have to survive forces far greater than that of a land based model with the wings, fuselage and skis taking the direct impact on landing. Anyone who has waterskied can attest to the hardness of water above 30kts!

350E16ED-E321-44F6-9CC7-F0F397482B95 by Alex Jones, on Flickr

350CDB7A-E439-4B26-818F-5FF6802A1E5F by Alex Jones, on Flickr

During the first lockdown here in the UK I measured the CG by using an ‘A’ frame belonging to a swing and some block and tackle, our garden is barely big enough for the model but needs must and it wasn’t as if I had anything else to do. The real SeaDart had a hoist point over the CG and ours was designed the same so it could be lifted safely at this point. I was surprised and relieved when it balanced as I had intended, I’m sure it will require some tweaking but as a starting point we’re good to go.

IMG_4061 by Alex Jones, on Flickr

[barrie burton]

Alex,another thing that you should be praised for ,is the quality of the photographs,please dont say they are taken on a mobile phone.I suspect that a lot of our members saw the 'Spitfire factory',what surprised me was the fact that when the Greek owners came to view their £2.5 million Spitfire,they used a mobile phone to photograph it,I woul have thought that it warranted a Cannon or Nikon

Barrie B

[Peter Siggins]

This is so far in front of modelling and the patience to get everything as near perfect as possible is mind blowing.

Whilst it was on the “swing” did you weigh it ?

Looking forward to seeing video of the flights and wish you every success in achieving maiden fights.

Pete

[Alex Jones]

Thanks guys... The model does get treated to a Nikon occasionally

As you see it on the swing it was 91kgs so around 200lbs which is within the tolerance we expected.

The moment I’ve been most looking forward to for years is getting the model in the water for the first time. There are so many possible problems that we’ve had to overcome purely in a theoretically sense. Time to see if it works in practice. No pressure then….

There are so many unknowns that we have to take the testing slowly ticking off each item as we go while gently building up to the more exciting stuff.

We found a suitable lake close to Cambridge for the initial tests at Dams Watersports in St Neots. The team there were very friendly and supportive and provided everything we needed. It is not an easy thing to explain to a company outside of the industry and I had some interesting reactions in my search for a suitable site. Most of these reminded me of that scene in Top Gun where the guy in the back seat exclaims “you’re going to do what” accompanied with some eye popping then a polite “no”.

We plan to test the buoyancy and general handling at slow speeds before we start to stretch its legs and get the aircraft to plane on its skis. The smaller North lake was chosen for the initial tests as its size was good for the first round of slow speed tests. The longer stretches on the south lake can be used for the higher speed runs if all goes well.

4911C8F4-5502-4F68-9E90-AD2DE44302A9 by Alex Jones, on Flickr

There is no escaping the fact that this is a complicated model and it does need a checklist to ensure nothing gets missed. A lot of time has been spent in the background on this checklist and checklists for the various tests.

38F94CAC-795F-458A-931E-236A11BB266D by Alex Jones, on Flickr

The weather looked kind for the the days we had arranged so an early start got us on site at 0700. We found the lake had large deposits of floating weed which had only appeared in the last few days. When I scouted the site out the condition of the three lakes was perfect and I hadn’t considered this might change. For the slow speed work it didn’t matter but some thought would be required to find a clear path for any high speed runs. Much of the first day would be spent by the slipway anyway...

37C65705-705E-4129-B4AC-2E4B0884D685 by Alex Jones, on Flickr

8E39FD32-54C3-492A-BF2F-992EE8F8DBCE by Alex Jones, on Flickr

[Alex Jones]

The first job was to get the model in the water and do a basic leak test along with checking the buoyancy. It needs to sit at the correct waterline or it will just look odd when compared to the real aircraft. Thankfully it worked out well… We did have a leak in the rear bulkhead where the rudder servo wire comes into the dry section of the hull. Unfortuantley this did cost us 3 hours as we had to get the aircraft out of the water dry the area, remove some internals before sealing the leak and putting it back together again. It was a bodge job but allowed us to carry on for the day… subsequently the model stayed in the water for over 5 hours without issue but it will be properly addressed before the next set of tests.

Sitting ready to go into the water for a second time.

_DSC7839 by Alex Jones, on Flickr

No leaks and sitting how it should, time for some fuel...

_DSC7849 by Alex Jones, on Flickr

_DSC7857 by Alex Jones, on Flickr

[Alex Jones]

I invited Dave Wilshere to come and take a look at the model and do some of the initial tests. I always value his input and I know he'll say exactly what he thinks good or bad which is what a project like this needs.

I think he enjoyed getting everyone soaked during the engine runs.

https://youtu.be/Vbk2ZlXdLF0

[Alex Jones]

A few pictures from the first test…

The model coasting out for the first time on one engine as the other starts to spool up.

_DSC7862 by Alex Jones, on Flickr

_DSC7866 by Alex Jones, on Flickr

And another with the model disappearing a haze of spray.

_DSC7890 by Alex Jones, on Flickr

I am biased but it was much more impressive in person than the photos perhaps show. The rooster tail is over 30ft long and about 9ft tall coupled with the noise of the two 300’s did make it a real spectacle. It did really blow my mind as it was much more realistic than I ever imagined or hoped it would be. This is only one small step along the path to flight and ultimately in will only be a success if it flies as well as I hope but for the time being I’m happy with its progress.

The engine runs did cause a few issues, disappointedly but not surprisingly when the exhaust shroud is installed the engines make a great paint stripper! The good news is that it is purely aesthetic as we used a specific resin system that can cope with the temperatures caused by the efflux. The composite wasn’t damaged or even soft to touch after extended running on the water at slow speeds and high power settings so it would appear to cope with the worst case scenario in regard to cooling i.e very little bypassed ram air that you would have if in flight.

We should have used high temp paint from the start so we’ll see how a coat of heat resistant stuff does on the next test or maybe use aluminium tape and try and make it look scale that way… It does need some thought and any suggestions are gratefully received. It is a problem the full size had so at least we are having the full scale model experience.

The other issue is that the backend is running hot and this only occurs with the exhaust shroud in place (large silver section at the rear) and I also believe only when the aircraft is in the water. When the model is running in the water at slow speed and high power settings we’re vaporising the water and producing super heated steam which is being drawn back into the thrust pipes, this can even be seen in some of our images and only occurs when the turbines are running above 80%. You can see a sort of fog form inside the shroud at these power settings which is really interesting, for me anyway. We did have some static 3D printed Nylon engine petals that looked great but were completely destroyed and the after burning light rings were also damaged. These have now been removed and two new thrust pipes ordered as a precaution. The molten Nylon also blocked what little cold bypassed air they might have been contributing to the heat in the rear. We operated the model for 25 minutes with both engines running in two separate tests so this does represent the worst case configuration for cooling. Our next set of tests will explore this area further with some infrared cameras and tufting of the exhaust to see what’s happening with the heat and airflow.

_DSC7874 by Alex Jones, on Flickr

There isn’t anything we can do to stop this as we want to keep the model scale and changing the entire backend isn’t an option. What we can do is be aware of the problem so when positioning to the takeoff area we use a low power setting and accept that for around 10 seconds we will be getting the back end very hot until the tail lifts from the water and the aircraft starts to plane on its skis, at this point it should start to cool again and once airborne will be getting a good amount of ram air through both intakes.

[Dave Kellett]

Hi Alex,
Yet again some really interesting information and photographs.
As you are getting closer and closer to its maiden flight, please don't think this is an irrelevant question, but because of its weight, will the CAA be in attendance for these test flights? or will it simply be classed as an Unmanned Aerial Vehicle with CAA dispensation (UAV), I.E Drone. And allow you to fly unsupervised so to speak.

Best regards and very good luck.

Dave

[Alex Jones]

Hi Dave,

If flown in the UK then it will need to go through the LMAs excellent over 20kg programme and all that entails. If operated abroad then we would need to have relevant permissions, initially we had intended to operate the first flights with a European Navy who have followed the project from the start but the pandemic has put a hold on things. It hasn't flown yet and I doubt we will be able to do anything until the Spring at the earliest but whatever happens it will require the correct paperwork and permissions.

[Timothy Huff]

Alex, do you know how the "petals" would be set on the real aircraft at slow "taxi" speed? I'm wondering if they needed a particular setting to prevent this steam in the thrust-pipes from occurring on the full-size machine. It's conceivable they need to(work) and be partially closed to accelerate the efflux and provide a smaller aperture for steam to enter? Have you the "pilot's notes"?

[Alex Jones]

Hi Timothy,

The petals would have closed a little with reheat, however the models static versions were well away from the efflux and with the engine runs at Buckminster without the shroud theses static elements were fine as they are mounted inside the the bypass. We will just remove them completely but have some removable versions for use when on display. I'm looking forward to exploring the heat issues further on the next test.