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US NAVY SeaDart F2Y (Flying boat) Build

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US NAVY SeaDart F2Y (Flying boat) Build

Old 09-25-2020, 01:12 PM
  #351  
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Unusual that you didn't use mil spec circular connectors?

Seem they would be perfect for all your internal connections.




Regards,
Old 10-28-2020, 08:41 AM
  #352  
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What happened to this? Put on hold? Sure is fantastic.
Old 11-03-2020, 06:08 AM
  #353  
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Apologies for not updating this sooner, due to the tightening of restrictions here in the UK we could no longer carry out any testing, therefore we shifted focus to our other projects. I’ll continue to update the thread over the next few weeks as we’re not yet at 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.

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

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Please note these are not current pictures, the various COVID restriction we now face here in the UK were not in force when these images were taken.
Old 11-05-2020, 06:48 AM
  #354  
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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.



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Old 11-06-2020, 03:06 AM
  #355  
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With the model ready for the initial engine runs we took it the BMFA at 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 we are getting closer. 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.



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Old 11-06-2020, 04:07 PM
  #356  
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That Sir, is STUNNING!!!
Old 11-06-2020, 05:31 PM
  #357  
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Outstanding!!!
Old 11-07-2020, 05:10 AM
  #358  
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Thanks guys... I'm not going to be able to put off the flying bit for much longer



Phil from Fighteraces sent me a short video he took on his phone of the engine runs, Phil you need to get a better phone! []






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.



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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.



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Old 11-08-2020, 03:16 AM
  #359  
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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. Like the full-size this is more akin to a flying boat. It will have to survive forces greater than that of a land based model with the wings, fuselage and skis taking the direct impact on landing.



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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.



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Next stop the water...
Old 11-09-2020, 02:41 AM
  #360  
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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.

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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.

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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...

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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.

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

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Last edited by Alex48; 11-09-2020 at 02:44 AM.
Old 11-09-2020, 03:43 AM
  #361  
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Congrats Alex.. that looks amamzing (and cold )
Old 11-09-2020, 03:56 AM
  #362  
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Thanks Paul, although I'll only ever be happy once its flown successfully but I'll take this for the time being. The water temperature must have been at least 4 degrees! tropical for the UK... at least there isn't anything in there that will eat me!

I invited Dave Wilshere to come and take a look at the model as 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


Last edited by Alex48; 11-09-2020 at 04:10 AM.
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Old 11-09-2020, 05:42 AM
  #363  
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Jolly good show gentlemen!!

I’m a huge believer in checklists! I’m the only rc pilot I know that carries checklists at every flight!

Certainly, this masterpiece deserves a check list!
Old 11-09-2020, 10:11 AM
  #364  
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It was great fun driving the world’s largest-complicated-valuable model jet ‘speed boat’ around the lake, it’s amazing how Alex produced something that complicated, that was on the water for several hours without a hitch and barely a thimble of water inside. That and the owner who just ‘loved’ what had been achieved, he was literally a kid at Xmas beaming with happiness and pleasure from just watching his baby take it’s first steps.

It’s all been said, but the team involved with this have taken model jets to a completely new level.

Old 11-09-2020, 10:12 AM
  #365  
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Originally Posted by Alex48 View Post
Thanks Paul, although I'll only ever be happy once its flown successfully but I'll take this for the time being. The water temperature must have been at least 4 degrees! tropical for the UK... at least there isn't anything in there that will eat me!

I invited Dave Wilshere to come and take a look at the model as 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

https://youtu.be/Vbk2ZlXdLF0
That was only one turbine...imagine how wet we would all have been with both at that time 😄
Old 11-09-2020, 11:19 AM
  #366  
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Who's doing the first flight...??
You doing it Dave?

Not one I'd be volunteering for!
Old 11-09-2020, 12:25 PM
  #367  
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I guess the owner will make that decision when the time comes. Sensibly it’s been tested in stages, chasing it in a speed boat as we did, it can be taken right onto the step and ‘skipped’ it will be fine, the saying it looks right guarantees success.
Old 11-10-2020, 05:13 AM
  #368  
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I'm very much looking forward to the next set of tests. A few pictures from the first test with Dave at the controls, thanks Dave.

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

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And another with the model disappearing into a haze of spray.

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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 but for the time being I’m happy that it floats.

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 there 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.

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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.


Last edited by Alex48; 11-10-2020 at 03:20 PM.
Old 11-10-2020, 02:09 PM
  #369  
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wow... that is an amazing project! Great job... can't wait to see some more videos!
Old 11-10-2020, 03:11 PM
  #370  
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It is awesome to see the progress. Love the pics and vids
Old 11-11-2020, 05:41 AM
  #371  
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wow !! amazing !!!

... that rooster tail is impressive but at the same time is a risk to hide the model during take-off?
Had this hapen once to me when i took of with smoke and cross wind..

congratulations for your work!
Old 11-11-2020, 12:42 PM
  #372  
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Once it’s on the skis clear of the water most of this goes. This is just while taxiing at lower speeds
Old 11-12-2020, 06:03 PM
  #373  
Spencer K
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I hope this goes better than the full scale. Lots of guys died trying this stunt 🙈
in all seriousness, good luck for a really cool 😎 project!!
Old 11-13-2020, 02:09 AM
  #374  
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Originally Posted by Spencer K View Post
I hope this goes better than the full scale. Lots of guys died trying this stunt 🙈
in all seriousness, good luck for a really cool 😎 project!!
Only one crashed...
Old 11-13-2020, 06:20 PM
  #375  
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You’re right, i thought I remembered several. Looking forward to a video of your beautiful model!

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