Convair YF2Y-1 Sea Dart

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Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » August 2nd, 2019, 4:57 pm

Hi Guys,

The pilot now has his Go Pros Session head attached, this is easily interchangeable with the scale head. Head movements are controlled by a separate transmitter and all the hand and foot movements are tied into the aircrafts flight controls.

Image_DSC6312 by Alex Jones, on Flickr

I'll upload a short video tonight which should explain things a little better.

Cheers

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » August 2nd, 2019, 5:31 pm

Here is the short video of the above.

https://www.youtube.com/watch?v=fUFfRHHpMC0

Nigel Cox
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Re: Convair YF2Y-1 Sea Dart

Postby Nigel Cox » August 3rd, 2019, 7:34 am


Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » August 3rd, 2019, 9:24 am

It's a great bit of footage. The first SeaDart was very underpowered as the engines the designers had hoped to use were still in development so they had to use J34's (3400lbs). As the video shows it struggles. The later SeaDarts had the more powerful after burning J46 (6100lbs). the power to weight ratio on the first SeaDart was only 0.29! with the more powerful engines they got this up to 0.5. Interestingly modern deltas with a similar configuration to the SeaDart like the Mirage 2000 have a power to weight ratio of 1.1 with reheat. I'd like to see a SeaDart with that kind of power! :) The best our model will have is around 0.85 and seconds later will run out of fuel so a realistic figure would be around 0.75-0.8. You can't read to much into these figures in isolation but the geek in me enjoys the comparisons. Sorry I digressed a little...

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » August 8th, 2019, 6:44 am

Jumping ahead a little before I start talking about the rear fuselage build...

A quick photo with all the guys involved in the original pattern build and now the paint prep and paint of the final flying model pictured here. FighterAces are doing a great job as usual :)

Image_DSC6321 by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » August 11th, 2019, 6:58 am

Moving on with the build…

I’ve covered the builds of the forward fuselage, ski retraction, animatronic and cockpit. All of these need finishing off but that will be after the model is painted, so bear with me.

Next on the list is the rear fuselage. This has been tricky as I’ve had to re-design some areas to accommodate the new ski actuators which went through several iterations. I also failed to take into account the increase in skin thickness over the curvatures of the airframe plus I re designed a few formers to save some weight. All this meant that there was a lot of fettling.

Everything is interlocked which helps transmit the loads but also means everything has to be bonded at the same time or at least clamped into position while some of the structure is bonded. The rear fuselage formers dictate where the wing spars are and by extension the wings, if out of alignment then the wings won’t fit or be square with the airframe. The same can be said for the vertical stabiliser. What this means is that I have to assemble the whole model, dry fit everything, square the wings and vertical stabiliser and assess what areas need trimming and repeat the process until all the formers are seated correctly. The intakes need to be installed as these bolt onto the formers and it is important they have a tight seal onto the formers and run in the correct alignment. Now, I don’t want to sound like I’m moaning because I love being part of this project but assembling and dissembling the model got old very quickly!! I lost count… and started wondering if a 1/8th version might have been a better idea :)

The last time I was seen smiling for around 2 months. :)

ImageIMG_0404 by Alex Jones, on Flickr

The carbon seat component for the vertical stabiliser.

ImageIMG_0441 by Alex Jones, on Flickr

The turbines had to be installed and aligned also during this process.

ImageIMG_0476 by Alex Jones, on Flickr

The aft bulkhead former and ducting dry fitted in place.

ImageIMG_0474 by Alex Jones, on Flickr

Checking the alignment of the wings and vertical stabiliser.

ImageIMG_0528 by Alex Jones, on Flickr

Finally all the rear formers bonded into the correct position. Yay :)

ImageIMG_0847 by Alex Jones, on Flickr

Dave Kellett
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Re: Convair YF2Y-1 Sea Dart

Postby Dave Kellett » August 11th, 2019, 12:20 pm

Hi Alex,
You and your team never cease to amaze, a truly amazing project.
Hope this is relevant, but does the model have a water rudder? as do some float planes.

Best regards
Dave

PS. I still think it's got to the bum twitching cycle clip stage.:)

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » August 11th, 2019, 10:43 pm

Hi Dave,

Thanks... it did have a water rudder which we have replicated. It would open to 30 degrees in the water and act as a water rudder while in flight both doors would open to 60 degrees and act as a speed brake. The only picture we have of them open is below and this was likely taken long after they were decommissioned.

ImageWater Rudder by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » August 26th, 2019, 12:17 pm

With all the main formers bonded in place it’s time to fit the fuselage wing roots. These tie all the formers together along with the keel beam. Once trimmed and fitted correctly I bonded them in place while taping and clamping the wing. I had to do one at a time and also check the wing alignment just in case! This was more work than these three pictures make it look!

Prepping the fuselage wing root.

ImageIMG_0488 by Alex Jones, on Flickr

The root plate taped to the wing to ensure a good fit. I also clamped the wing to the fuselage (not pictured).

ImageIMG_0494 by Alex Jones, on Flickr

The root plates bonded in place.

ImageIMG_0490 by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 5th, 2019, 8:19 am

With the aluminium wing roots bonded in place I filled the step between the bonding surface and composite ready to lay some kevlar over the join.

Step filled

ImageIMG_0504 by Alex Jones, on Flickr

Kevlar cut ready to wet out with resin.

ImageIMG_0507 by Alex Jones, on Flickr

You may have noticed the two holes in the ski wells. These were cut to help with trouble shooting on the ski retraction and the other was cut to help with symmetry. These were cleaned up and boxed in with carbon. I hastily made clamp consisting of air rams and duck tape when I realised what I planned to use didn’t work.

ImageIMG_0509 by Alex Jones, on Flickr

This section of the airframe has had some abuse! It has seen several iterations of structure and ram positions not to mention the pivot block which I had to remove after my own stupidity jammed the main pin into the block. The damage is all superficial so it’s in need of a coat of paint. I’m looking forward to erasing those memories with my airbrush :)

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 10th, 2019, 6:39 am

All the internals now painted green, a few more bits of structure to add that would have been in the way then I can look at bonding the top fuselage on.

ImageIMG_0521 by Alex Jones, on Flickr

ImageIMG_0519 by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 11th, 2019, 3:21 pm

Next on the never ending list is to prep all the formers ready to bond on the top composite fuselage section.

The Tridair anti-vibration fittings have been installed, these secure the forward fuselage section to the aft. We also have a large carbon tube running through both sections and finishes just aft of the forward ski mechanism.

ImageIMG_0542 by Alex Jones, on Flickr

ImageIMG_0543 by Alex Jones, on Flickr

The carbon seat for the vertical stabiliser bonded in place.

ImageIMG_0541 by Alex Jones, on Flickr

ImageIMG_0544 by Alex Jones, on Flickr

The intakes have to be installed as they secure against some of the formers so ensuring these are in the correct place is important while we bond the top section.

ImageIMG_0549 by Alex Jones, on Flickr

ImageIMG_0550 by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 12th, 2019, 9:13 am

I’ve assembled the auxiliary intakes and dry fitted them in place. Cutting all the apertures is not a job I want to repeat any time soon. :) The final fitting will be after the paint work is completed. They are bonded to the intake but to facilitate removal for maintenance they will be sealed with silicone onto the fuselage. I hope they don't need removing often but the intakes need to come out to maintain the tanks and rear ski mechanisms so they do need to be removable if I have any issues with these. In hindsight I would split the intake again just forward of the main hatch so the tanks and retraction mechanisms could be maintained without the auxiliary intakes needing to be removed. Fitting these will be one of the last jobs on the final equipment installation.

ImageIMG_0477 by Alex Jones, on Flickr

The unit is all 3D printed with the frame in SLS nylon and the doors manufactured by SLA. The intake doors open automatically when at high thrust settings and slow aircraft speed either at half or full depending on the thrust. They open into the main intake ducting so work prototypically.

ImageIMG_0481 by Alex Jones, on Flickr

A short video demonstrating their movement. The video has no sound incase you wonder.

https://www.youtube.com/watch?v=AhWylmR1rjI

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 13th, 2019, 7:59 am

Installing the main wing root into the wing which I thought would be easier before fitting the top fuselage composite.

ImageIMG_0551 by Alex Jones, on Flickr

ImageIMG_0552 by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 14th, 2019, 12:27 pm

The engines installed and centred to ensure nothing pulls out of alignment with the top is clamped into place.

ImageIMG_0475 by Alex Jones, on Flickr

Hysol in place ready to receive the top, this is a two man job and requires us to prize the top section open slightly while lifting the section over and positioning on the correct location so the glue ends up where it needs to be. All the hatches have been installed and secured with duck tape to avoid any unwanted deformation.

ImageIMG_0596 by Alex Jones, on Flickr

ImageIMG_0589 by Alex Jones, on Flickr

A good 24 hours later I removed all the hatches and ducting. The bond joints were inspected and the fillets increased in size using more Hysol.

ImageIMG_0580 by Alex Jones, on Flickr

I deliberately didn’t try and bond the rear lower seams until the top had cured. These will be bonded with Hysol then reinforced with carbon tape. The rear most former also needs to be installed along with building the exhaust section.

ImageIMG_0609 by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 15th, 2019, 8:58 am

The exhaust section is removable and consists of of one rear former with two carbon rings of a slightly small aperture diameter. The ducting is flush with the inside of the carbon when in place. An o-ring is installed into the the gap between the smaller diameter carbon and larger diameter glass. The exhaust section is then bolted on from the inside pulling it flush with the rear most fuselage former and compressing the o-ring creating the seal.

The inside face of the exhaust former.

ImageIMG_0634 by Alex Jones, on Flickr

The outside face of the exhaust former, note the groove created by the differing diameters which is where the o-ring will sit.

ImageIMG_0635 by Alex Jones, on Flickr

Bonding on the rear most fuselage former with the exhaust former bolted in place waiting for the composite to be bonded.

ImageIMG_0636 by Alex Jones, on Flickr

Bonding the composite exhaust section onto its formers.

ImageIMG_0637 by Alex Jones, on Flickr

Everything removed and checked, also note the carbon tape reinforcement on the rear seam line.

ImageIMG_0631 by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 16th, 2019, 8:04 pm

I didn’t take any pictures of the tailwheel structure installed but I do have the CAD renders and a shot of the parts which you can see below. I’ve tied the axlel structure into the keel beam using 3mm carbon plate. We have a 1mm thick carbon fairing that then goes over this as pictured so it all looks like the full size.

ImageTLJC SeaDart Model 25_07_17 v662 by Alex Jones, on Flickr

ImageTLJC SeaDart Model 25_07_17 v664 by Alex Jones, on Flickr

ImageTLJC SeaDart Model 25_07_17 v669 by Alex Jones, on Flickr

ImageIMG_0624 by Alex Jones, on Flickr

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 17th, 2019, 12:35 pm

While on the subject of wheels...

The original concept was to have the aircraft ingress/egress the water via a slipway under its own power and independent of any ancillary equipment. The first SeaDart tested had a tailwheel and two fixed wheels in the aft portion of the skis.

Image4561375515_08ede9ee14_o by Alex Jones, on Flickr

This worked well, however, the twin skis caused severe vibrations as the ski flexed between the forward and aft ski attachment points. Interestingly when testing their scale models this wasn’t present (fingers crossed). On the second SeaDart the fixed wheels were removed to concentrate on the ski hydrodynamics, this is the best SeaDart twin ski variant from a hydrodynamic perspective, also the only SeaDart to go supersonic and the aircraft we have chosen to model. This variant kept the tailwheel but had a beaching dolly. The wheels sat under the aft section the skis and fixed forward with bars onto the forward ski mechanism. Divers were used to remove and attach the dolly once the aircraft was in the water.

Image31792048724_a360346ab5_o by Alex Jones, on Flickr

Image31792049394_a0389d559a_o by Alex Jones, on Flickr

The third SeaDart went back to having wheels on the aft of the skis but these rotated through 90 degrees when in the water...

ImageIMG_0007 by Alex Jones, on Flickr


I suppose this is a good point to share our plans in this regard... We have designed a dolly for the model which can be converted into a scale dolly by removing all the aft section rear of the wheels. So this will look very similar to the above pictures. The model can then sit on its own and move under its own power if desired.

For maintenance and testing purposes before we put the model in the water the dolly can be used to support its full weight using the full length non scale version. Ski retraction and oleo extension can be tested and we can also run the engines with the model sitting on the dolly. Our model is large and heavy so it’s important that it can be moved around easily and hopefully this will achieve that. The dolly uses disc brakes on the main wheels with a steerable wheel at the back. Below is a CAD render of our dolly designed by our engineering partners Performance Engineered Designs. Along with the dolly PES also helped work through the ski retraction system and scan the original pattern for us. They have shown great enthusiasm for the project and sponsored much of the design work so a bit of a shout out to them for all they have done so far. :) It helps when the MD and and Technical directors are aircraft enthusiast :)

Our Dolly hasn't been built yet but all the design work and engineering drawings are complete.

ImageDolly Assembly (with mirror parts) v4-2 by Alex Jones, on Flickr

Cheers, Alex

David Baker
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Re: Convair YF2Y-1 Sea Dart

Postby David Baker » September 17th, 2019, 1:37 pm

Hi Alex
Now the project is so well advanced and most of the sub assemblies are nearing completion....
Have you weighed it all yet? do you think the weight will be in the right place for the c of g and for its “sit in the water”
Have you calculated the wing loading yet?
Thanks
David

Alex Jones
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Re: Convair YF2Y-1 Sea Dart

Postby Alex Jones » September 17th, 2019, 6:49 pm

Hi David,

The CG is in the same place as the original so it should sit in the water correctly (fingers crossed). 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. These are similar to the loadings of the other jets we've built with success.

We did weigh the complete fuselage last month and it was 39kgs which was 1kg lighter than I had calculated in CAD so its looking like it will be on target.

Cheers, Alex


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