The Model (Phase 4)

As I said in my last post we decided to support the main pivot externally which is exactly what they did on the full size. I assume for a similar reason. We tried to keep it as scale as we could within the confines of actually having a functioning part. The top hat is removable to allow the main pivot to slide out if required for maintenance. Like before all the tolerances have been reduced and it the top hat runs on a PB bush. This works as expected and removes all play in the pivot.

by Alex Jones, on Flickr

by Alex Jones, on Flickr
With the relief of finally having two functioning skis we can turn our attentions elsewhere. Part of the brief was to get realistic in cockpit footage to try and recreate what it might have been like to fly this aircraft. There are three separate camera angles, one behind the pilots shoulder, one looking up from behind the rudder pedals and a head camera on our pilot. With the brief in mind we decided on a fully functioning animatronic pilot. We’re using servo driven flight controls that will move the pilot. The below images show the mechanics of this.

Flight Control Stick

by Alex Jones, on Flickr

by Alex Jones, on Flickr

Thrust Levers

by Alex Jones, on Flickr

Everything mounted in place including the mechanisms for the rudder pedal movement.

by Alex Jones, on Flickr

Parts are a mixture of 3D prints using SLS and CNC’d Aluminium. We had to make a few changes form our initial designs which included larger servos and some reinforcement but after this it all works nicely.
I’ve always enjoyed building small plastic models although time constraints mean I haven’t done so for years but I do still have all my paints and weathering materials etc… many of the techniques used by the plastic modeller can be scaled up to suit our needs. I started by doing some subtle weathering to the floor and rudder pedals using several different enamel washes and pigments. Using a water based paint for the base colours you can then use an enamel wash and work this in using a brush wetted with sprit until you have the level of weathering you desire. Dry pigments used sparingly can add some depth. It’s subtle at this stage but when applied to everything in the cockpit I hope it will soften it and make it look more realistic. (Fingers crossed)


by Alex Jones, on Flickr


by Alex Jones, on Flickr
This is short video showing the movement of the flight controls. The flight controls drive the pilots movements hopefully giving the effect of the reverse once we tweak the speeds and throws etc... less is so often more.

Last edited:
Hi Everyone,

It’s good to be finally updating these threads on the SeaDart… and this time I will be posting until completion. I aim to update the thread every few days so keep an eye out if you are interested in the models progress.

The majority of photos I will be posting are just from my phone so do excuse the photography… These were designed for quick client progress shots during the build so he could catch anything he was unhappy about before anything becomes too difficult to rectify.

My last build post was detailing the cockpit assembly so this seems a good place to pick up our progress.

The next part of the cockpit is the seat. This was designed in CAD and the whole bucket element 3D printed. I wouldn’t ordinarily recommend SLS nylon prints for scale parts as the finish isn’t suitable and can’t easily be made good. However for the seat where much of it isn’t seen and some of the areas with visible build lines are capped with lithoplate it can work.

The pictures don’t really do the finish any favours as in reality everything is much softer on the eye. The seat was painted in several shades of grey and weathered with dry pigment. You can’t use a wash on these parts as you just highlight the surface finish, so varying dry paint pigment colours are used to create a similar effect.

The seat painted in the base colour.

by Alex Jones, on Flickr

Layers of great and pigment being added.

by Alex Jones, on Flickr

The seat in place with the custom parachute. We aren't happy with the harness buckles the next post will focus on the design and build of these. :)

by Alex Jones, on Flickr
Changing the subject a little...

Would there be any interest in people visiting us during the water-based testing here in the UK? (no flying) It will be the hydrodynamic tests, fast, slow, turning, deplaning water taxi tests etc... We could do a talk on the aircraft and people could have a good look around the model and see some of our testing. Just an idea but I get a lot of emails asking for visits so this might be of interest to some. I don't believe this will be going to any shows and obviously couldn't fly at most anyhow so the chances of seeing the model are limited. If anyone is interested please send an email or PM me here on the forum with your name and email and I'll get back to you.

Onto the harness…

We want the harness to be scale for several reasons. We need to remove the pilot so why not have a working prototypical harness. There are three camera angles in the cockpit for, one of these is looking up at the pilot with the instrument panel removed so the harness is very visible at this angle. With the pilot strapped in correctly the body movement is more realistic as he is constrained in the correct way. This should all add to realism

The harness design was done by Ralf at and manufactured at Horbach Technik in Germany. The parts are 3D printed then cast. Its lockable using super elastic NiTi 0.012mm wire.

Ralf has done an excellent job with the harness positively locking well and also being very strong so handling isn’t a problem.

This is one of our research shots showing some of the SeaDart harness.

SeaDart Harness
by Alex Jones, on Flickr

Ralfs initial deign work.

Harness Design
by Alex Jones, on Flickr

The final product installed into the seat with the custom made parachute on the seat.

by Alex Jones, on Flickr

A short video showing the harness working.

Last edited:
On with the ejection seat… The headrest is a mix of SLA resin prints and Nylon SLS. The straight tubes are plastic except the centre ejector rail with is Carbon. The plastic tubes contain the antenna for the pilots head movement which is controlled from a separate transmitter. I have more detail to add but I will do the last little bits when fitting it to the airframe. I still need to work on the left and right panels, I’m just waiting for some water jet cut parts to arrive before I start.

SeaDart Ejection Seat
by Alex Jones, on Flickr

SeaDart Cockpit
by Alex Jones, on Flickr

Next on the list is to install the camera which is interchangeable with the pilots head. Hopefully this will give a decent pilots eye view of proceedings, the camera will be able to move just like the head.
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.

by Alex Jones, on Flickr
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 :)

by Alex Jones, on Flickr
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. :)

by Alex Jones, on Flickr

The carbon seat component for the vertical stabiliser.

by Alex Jones, on Flickr

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

by Alex Jones, on Flickr

The aft bulkhead former and ducting dry fitted in place.

by Alex Jones, on Flickr

Checking the alignment of the wings and vertical stabiliser.

by Alex Jones, on Flickr

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

by Alex Jones, on Flickr
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.

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).

by Alex Jones, on Flickr

The root plates bonded in place.

by Alex Jones, on Flickr
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

by Alex Jones, on Flickr

Kevlar cut ready to wet out with resin.

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.

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 :)
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.

by Alex Jones, on Flickr

by Alex Jones, on Flickr

The carbon seat for the vertical stabiliser bonded in place.

by Alex Jones, on Flickr

by Alex Jones, on Flickr
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.

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.

by Alex Jones, on Flickr

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

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

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.

by Alex Jones, on Flickr

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.

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.

by Alex Jones, on Flickr
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.

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.

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.

by Alex Jones, on Flickr

Bonding the composite exhaust section onto its formers.

by Alex Jones, on Flickr

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

by Alex Jones, on Flickr