Convair YF2Y-1 Sea Dart

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Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 18th, 2019, 6:13 pm

The Elevons are constructed from carbon skins, carbon ribs and a Rohacell core. This is cold bonded in the CNC’d tooling cradles to ensure they keep the correct shape. The pattern had a little reflex built into the elevons and wing tips. The elevons are incredibly strong by design as they will take some punishment being on the water line. They attach with a 2mm steel wire which runs the length of the elevon and the pivot blocks are correct in number and location as per the original aircraft. Thanks to Steve for pointing me in the right direction with regard to sleeving for the 2mm wire. :)

The construction and finished components.

ImageIMG_0557 by Alex Jones, on Flickr

ImageIMG_0626 by Alex Jones, on Flickr

ImageIMG_0657 by Alex Jones, on Flickr

ImageIMG_0656 by Alex Jones, on Flickr

The main issue we’ve had is the elevons are impossible to balance in themselves and the actuation is on the pivot so there is no moment arm to help the servos. We didn’t want servos in the wing due to the the bottom of the wing sitting on the water and we didn’t like the idea of having them in the top of the wing. I originally planned on two Ditex servos ganged together actuating the elevon from within the fuselage. It was immediately clear that this was problematic, it works in CAD but just didn’t feel right once installed. It’s one thing to look at the numbers on the screen but there is no substitute for actually doing it and deciding. I used one servo to test the geometry with the telemetry feedback from these servos proving very useful. I had never been entirely happy with the set up so it didn’t come as much of a surprise to see the servo struggle. Just to hold the elevon neutral required 7kgs of torque. There are arguments that the static flight loads on the servo will reduce when neutral etc... when your sentence starts with “it will probably be fine” you know it’s time to go back to the drawing board. :) To move the elevon at any speed to full deflection was causing the servo to peak at its maximum torque. Even with two ganged together theoretically halving the required torque it still didn’t fill me with any confidence. There was discussion around using larger servos with the same geometry but this doesn’t solve the underlying problem so it was decided that the actuation needed to be re-designed.

The torque requirements of the surface aren’t outrageous considering its size. A deflection of 40 degrees at 100kts and 12 degrees at 250kts requires around 1000ozin of torque but our new set up will far exceed this. The full size had a maximum elevon deflection of 40 degrees up and 29 degrees down.

Talking with the Phil and John at Fighteraces we came up with a much better way of doing things. The one thing we are not short of with this model is space in the fuselage. This allows us to counterbalance the elevons inside the fuselage. We then decided on using two SP50 servos per elevon mounting them over the CG and using carbon pushrods to the pivot arm. These servos are powered separately and at 8.4 volts produce a combined torque of 183kgcm (2540ozin). By mounting the two servos in an orientation that allows a plate to be fixed between the two servo arms we can cut a slot in one of the fixing points to the servo horn allowing the elevon a degree of freedom even if one of the servos failed in a fixed position. This is nothing new and used in large models without issue it’s just now we can see a way to integrate that principle into the SeaDart. I’ll post some pictures once I’ve finished the design as the above might not make much sense. At least this is a modification which can be installed into the complete airframe without much issue.

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 20th, 2019, 4:13 pm

We’re at the stage where we can start to do the prep work ready for painting. There is a huge amount of work to do in preparation for paint, far more than I had hoped for. This is the airframe we’ve used for all our development work and aesthetically it is in need of some work. We could just shoot a layer of primer and paint without doing any remedial work on the aesthetics but that isn’t in the spirt of this project. We want things to be as good as possible.

For the prep and paint I can think of no-one better than Phil and his team at FighterAces. Thank you to Phil for taking on this project and spending so much time on it over the last few months. Delivery is planned at the beginning of October so what you see here will soon be the current state of the model. I’m sure Phil will chime in with his processes and answer any questions as I post the pictures.

To get the model to the level we specified will be around 6-8 weeks work, I’m sure it will be worth the wait! The first week in October will see the airframe painted and fully assembled for the first time, I can’t wait!!

On with the work…

Firstly all the hatches needs to be installed with catches and sealed from the water. This is no small task in itself. Secondly, all our development work has been done on this airframe so we need to build back raised panels, re-rivet areas, crisp up panel edges and generally get the model aesthetically up to the standard that is expected of this project.

The model spending its first day in its new home.

ImageIMG_0639 by Alex Jones, on Flickr

ImageIMG_0640 by Alex Jones, on Flickr

A weeks worth of priming, filling and panel work

ImageIMG_1393 by Alex Jones, on Flickr

ImageIMG_0651 by Alex Jones, on Flickr

I delivered the wings a week later, so a quick motivational shot with it assembled. From left to right, Graham, Phil, and John.

ImageIMG_1423 by Alex Jones, on Flickr

Grahams fist look at the single piece machined aluminium main spar… perhaps a caption competition for this one :)

ImageIMG_1418 by Alex Jones, on Flickr

David Baker
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Re: Convair YF2Y-1 Sea Dart

Postby David Baker » September 20th, 2019, 5:36 pm

Alex
My caption is.... “Now that’s what I call a spar!”

barrie burton
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Re: Convair YF2Y-1 Sea Dart

Postby barrie burton » September 21st, 2019, 7:52 am

Alex,a couple of questions I suspect a lot of viewers would like the answer to.Is this a one off order from a very wealthy customer,if so what is the ball park price,to the nearest £10K ? I suspect you now want me to go forth and multiply.Or is it a prototype for a new product line? I wont be offended if you tell me to mind my own buisness,honest !
A truly amazing project that all concerned can be justly proud. PS what radio are you using?

Barrie Burton

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 21st, 2019, 10:54 am

Hi Barrie,

This is a one off project and part of our bespoke service we offer... as for the cost, much of the project has had sponsorship from the various manufactures we have worked with. This has helped tremendously as we wouldn't have been able to do the project without it. As for the final cost... this is something that I would only discuss with my client.

Thanks for the interest and we're using a Jeti DS24 with two 2.4 receivers and one 900Mhz back up.

Cheers, Alex

Timothy Huff
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Re: Convair YF2Y-1 Sea Dart

Postby Timothy Huff » September 21st, 2019, 8:50 pm

Alex,

I'm really looking forward to seeing a diagram of illustration of the elevon servo setup. Does this bring the elevon c of g forward of the hinge-line (if I understand you correctly), and if so, does this have an impact on pitch-trim. I can't see any evidence of provision of a trim-tab, so I imagine this is dealt with by other means?

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 23rd, 2019, 9:17 am

HI Timothy,

The elevon will just be balanced better than it is now. The elevon CG will still be behind the hinge line like most control surfaces without counterbalance. It just means there is less torque requirement on the servos to move the surface. Sorry for the short reply but I broke my wrist on Saturday so my one handed typing takes forever!

Cheers

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 24th, 2019, 10:31 am

More work from the team at FighterAces, they have put a lot of hours in to get to this stage. Lots of attention being payed even to the smallest of details while they get the finish up to specification.

Blending the exhaust section into the fuselage and notice the exhaust with greater definition on the panels after a re-work. This was one section that was a challenge to mould, it required a 5 part tool and coupled with the the temperature specifications of the part meant we lost a lot of detail from the pattern. With some work they have recovered the finish nicely… In hindsight I would have made this part in sections as opposed to one piece.

ImageIMG_0705 by Alex Jones, on Flickr

ImageIMG_0706 by Alex Jones, on Flickr

ImageIMG_0713 by Alex Jones, on Flickr

I’m really looking forward to seeing it all one colour!

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 25th, 2019, 12:22 pm

I’ve spent some time in Durham helping finish up some of the parts. One of the areas I needed to focus on was the water rudder, hopefully the pictures will explain things, as always any questions please feel free to post.

The parts ready to assemble.

ImageIMG_0734 by Alex Jones, on Flickr

ImageIMG_0737 by Alex Jones, on Flickr

ImageIMG_0750 by Alex Jones, on Flickr

ImageIMG_0747 by Alex Jones, on Flickr

Both water rudders primed and ready to paint.

ImageIMG_0760 by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 26th, 2019, 9:09 am

Time for the guys to turn their attentions to the intakes. FighterAces made a silicon mould of the intake patterns and cast these with a tough resin. This area needs to be strong as I’m certain at some point someone will grab or hold the intake.

John de-moulding.

ImageIMG_0745 by Alex Jones, on Flickr

ImageIMG_0746 by Alex Jones, on Flickr

No one has ever seen John smile so this is included as evidence that he does or at least a grimace while trying . :)

ImageIMG_0757 by Alex Jones, on Flickr

The fuselage close to receiving its top coat.

ImageIMG_0765 by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 29th, 2019, 4:00 pm

We didn’t detail the ski well patterns originally so Phil spent some time adding the raised rivets in both the forward and aft ski wells. With this complete and the forward spray rails installed it was time for some paint. The different shades of blue are due to these panels being constructed from different material on the original so this has been replicated here.

ImageIMG_0768 by Alex Jones, on Flickr

ImageIMG_0872 by Alex Jones, on Flickr

This aircraft didn’t have many decals but the few that it does have are added using paint stencils.

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 30th, 2019, 9:35 am

Work on the vertical stabiliser… yellow is painted with the masks applied on top. These were cut by flightline graphics based here in the UK.

ImageIMG_0802 by Alex Jones, on Flickr

ImageIMG_0808 by Alex Jones, on Flickr

ImageIMG_0818 by Alex Jones, on Flickr

ImageIMG_0820 by Alex Jones, on Flickr

ImageIMG_0824 by Alex Jones, on Flickr

We are trying to replicate the original in every way including the hastily painted NAVY on the vertical stabiliser.

Dave Kellett
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Re: Convair YF2Y-1 Sea Dart

Postby Dave Kellett » October 1st, 2019, 12:02 pm

Hi Alex
Like so many others who are thinking the same as myself, what an amazing project.
This really does go to show off the skills of a very skilled team who I would consider to be the 'The best of British'
How was this project conceived? and why the Sea Dart?

Have you got a theoretical weight? and are you close to it?, also how long do you anticipate to achieve the finished project.

Thank you for posting all of these photographs, it really is enjoyable to see the Sea Dart progressing.

Best regards

Dave

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » October 1st, 2019, 12:24 pm

Hi Dave,

Thanks for the kind words, regarding the weight...

The dry weight should be close to 70kg and the full wet weight 85kg which gives a wing loading of 5.4lbs per sqft and an average of 4.9lbs per sqft based on its wing area of 35sqft.

I have some text from the client as to the 'why' which I'll dig out for you. From my point of view it was a commission, however, the subject has really grown on me and I love the unusualness of the subject and the water aspect should be incredible... fingers crossed!

Cheers

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » October 1st, 2019, 6:47 pm

The wings prep and paint, hopefully the pictures should explain things, if not feel free to ask any questions and I’m sure Phil will chime in.

ImageIMG_1796 by Alex Jones, on Flickr

ImageIMG_0780 by Alex Jones, on Flickr

ImageIMG_0821 by Alex Jones, on Flickr

ImageIMG_0829 by Alex Jones, on Flickr

ImageIMG_0860 by Alex Jones, on Flickr

The elevons are not installed or pictured as I want to makes sure that the new elevon system works and is fitted and bonded before these are painted. If the elevon is a slightly out then the stripes on it won’t look right as there will be a slight misalignment.

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » October 2nd, 2019, 8:33 am

Probably the most challenging part of the painting is the Aztec type pattern over the intakes. This took John a long time to get it to the stage that they were happy to commit to paint. The below pictures show the final stage of masking.

ImageIMG_0907 by Alex Jones, on Flickr

ImageIMG_0910 by Alex Jones, on Flickr

ImageIMG_0916 by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » October 3rd, 2019, 6:54 am

We’re nearly there… An enjoyable few days spent at Fighteraces going through the paint work before we commit to clearcoat. The following photos do come with a caveat… The paint work and weathering aren’t complete so some areas need work but you should get a good idea of the progress to date.

The aztec pattern completed bar a few tweaks.

ImageIMG_2189 by Alex Jones, on Flickr

The elevons aren't installed and the skis are only placed in the rough position but other than that I’m really happy with how its looking. More importantly the client is too. :) phew…. The elevons are huge so it doesn't look quite the same without them.

ImageIMG_2201 by Alex Jones, on Flickr

ImageIMG_2197 by Alex Jones, on Flickr

ImageIMG_2171 by Alex Jones, on Flickr

The plan is to have the airframe delivered back down south by the end of this month ready for us to start the equipment installation.

Thanks once again to Fighteraces for all their work on this.

Timothy Huff
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Re: Convair YF2Y-1 Sea Dart

Postby Timothy Huff » October 6th, 2019, 9:30 pm

Hi Alex,

I was wondering if you'd come across and any reference as regards the very vivid and unusual paint scheme? Although it's similar to, it doesn't follow the rules of "dazzle camouflage", so I can only surmise it was something to do with post-flight analysis of cine-film footage perhaps? It may of course be just because it "looks cool", so I'd be interested to know if such schemes were common in USN prototype aircraft of the period...

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » October 7th, 2019, 6:38 am

Hi Timothy,

The stripes on the back of the wings and vertical stabiliser were to help measure spray patterns and control deflections. The Elevons are missing in the above photos but continue the stripes seen on the rear of the wing. During the hydrodynamic phase of testing many more areas were yellow but our scheme is the toned down version from the press day in November 1954. The yellow was chosen for contrast but we don't know the significance of the Aztec type pattern. I can guess but we haven't found anything in our research that can tell us with definitively.

A picture of some of the guys involved. Left to right... Phil (Fighteraces), Alex (TLJC), John (Fighteraces), Ben (TLJC)

Photos courtesy of Philip Bloom.

ImageDSC09999 (1) by Alex Jones, on Flickr

An elevated shot from the front. The white fuselage in the background is a 1/4 scale SeaFury which might give it some scale for those that have seen a 1/4 scale SeaFury :)

ImageDSC00014 by Alex Jones, on Flickr


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