Vacuum laminated the board,
3x200g cfk plus 1x100g glass on the top side. 2x200g cfk plus 100g glass on bottom side. The bag needs to be big enough to go into the cavities on the top side, otherwise the pressure from the bottom is too hard and bends the bottom plate. Applied 0.6bar vacuum.
If I would do it again, I would not put the last layer of glass on top as this caused some visible spots where it is not transparent. It protects the cfk but without I would have got a cleaner cfk finish.
Seals
In my first build I used a self adhesive EPDM seal. It works well but it is not reusable. As it compresses and stays compressed, it needs to be replaced each time the box is opened. It is also annoying to remove the remainig adhesive with acetone.
As my new board has many seals, they need to be reusable/easily replaceable. Therefore I made them from Wagnersil 32N 2k silicone. The moulds were 3D printed.
I made this seal in two parts. First I made a flat 2mm thick seal on anacrylic glass plate with a frame cut from 2mm acrylic. Glued 4 3d printed space holders for the screw holes on that mold plate. This way you get a smoother surface than entirely 3d printed.
2nd step was to cut out the center opening for the cables. I cut it bigger than the opening in the board, installedthe seal, added a 3d printed mould part from the inside and poured silicone from the inside.
To my surprise the added silicone sticks to the premade part.
Connectors
Seals were not available when I ordered the Amphenol connectors, therefore I had to build them too.
Took it to the lake and put it under water.
Main compartment and receiver compartment are 100% waterproof but here was some leakage in the motor cabling compartment at the back. Not a desaster as the connectors and ultrasonic sensor that sits in there are waterproof. Need to troubleshoot, I guess either the round screw hatch or (more likely) the seals around the ultrasonic sensor leak.
ESC and elctronics
For the ESC I used a VESC A200Sv4.1, a replacement I got from a faulty v3. Not the cheapest option but it is well made and runs cool. To protect it from water, I put it in an extra aluminum case. The case is not 100% waterproof as I could not bother with cable glands. The compartment is waterproof, it is just an extra safety measure if some drops should get in. There is a 0.5mm heat pad between the ESC and the case. Between the case and the heat sink, there is only a thin graphite heat transfer foil, as the surfaces are flat. I lathed down the painting on the outside of the case. On the inside I just “machined” it on a drill press. The passive cooling works well, the VESC temp never exceeded 40°C so far.
Receiver and Minnie Logger are in a small box below the tube to the front. The loggers GPS module as well as the receivers antenna sit in the front of the board. Minnies BT/WiFi antenna sticks out of the box as it is only needed to transfer log data. I also added NTC temp sensors to the battery packs to log battery temp, it is connected to the motor temp inut of the vesc and logs unter motor temp in metr log.
Gadgets
As it is hard for me to read the display of the remote, I added some LEDs to display the voltage level of the battery. I built it into the lid of the receiver antenna compartment in the front of the board. I is made from a 32 segment 2812b RGB LED ring connected to an arduino.
The second feature is the flightAssis height measurement system. The vertical 8 LED bar indicates the height from the water level. There is an extra 5V 3A DCDC converter to supply the LEDs.
The horizontal 4 LEDs are status indicators. The lid is made from a sandwich covered with dyed fiberglass to allow radio signals to pass. The LEDs are really bright and readable in sunlight.
Batteries
I built two 14S11P Split Packs, one with Molicel P42A and one with P45B. To make them fit the through the screw hatch, I used a offset pattern for cell arrangement. I designed an Printed the cell holders and end caps. 7S is a bit more tricky than 6 (or 8S), as one of the busbars has to be at the bottom of the pack. I used 0.2mm nickel strips to spot weld the packs. Terminal leads are 6AWG with QS8 antispark connectors. I also put an ntc inside to log the battery temp (connects to motor temp input of vesc and logs as motor temp in metr).
2nd set of Batteries
For the second set I wanted to try something new, a copper nickel sandwich. It consists of a 0.1mm copper strip and 0.1mm nickel on top. I used a 3d printed template to form the strip and guide the stamp to stamp out a slot. Conductivity of copper is aprox. 4 times better than that of nickel.
I tested both battery sets and they work well, the P45B has slightly more capacity but not much, only 10% more. For a pack of this size it is not really worth the extra cost. For a configuration where you need high current per cell there might me an advantage to use the P45B.
Battery fixing system
I was tired of hock an loop bands so I chose a different way to fix the batteries. There are 3d printed thresholds on the side and at the back to keep the packs in position. The edge of the pack in the back is secured with a angled lever with 5mm pins. The pin locks with a spring on one side. It can be removed wit a 3d printed slider. All parts under load are made from aluminum, the 5mm pins are from stainless steel.
On your RL mast have you had the need or considered bonding the RL mast to RL mast plate? I find that there is a tiny bit of flex there using only the two mount screws and was thinking to inject epoxy or JB weld cement and steel bonding agent into that connection to remove flex and lock it tighter.
In this build I built my own mast from CFK. In my first build I only used the RL Fuselage and wings, not the mast, I used a chinese slinshot knockoff, which is really solid (and heavy). I do have an RL mast but never used it. I think the RL mast is not the most rigid one on the market, not only the junction between mast plate and mast but also rigidity of the mast itself. But it is relatively low cost, to be fair.
When sketching masts i found the the rl mast has the same profile as the f1 but rl is about twice the thickness. Maybe the grade of alu can be lower on the rl but i think it’s definitely not the flexiest mast out there. Gong v1 mast comes to mind
Built a top cover plate for the mast for transport. This keeps the Wagnersil silicone seal in place and allows to fix the phase cables. It also “stores” the fixing screws.
I also need to build a part to secure the motor for transport as this is the most delicate part of my system. The motor is over 2kg and has quite a bit of lever force. Still thinking on how to build an easy to remove sopport for the motor…
Season is ending, time for a 1st conclusion. I made around 600km on the new board and really like it. If I’d start over I would build the mast slightly angeled to the front to get a better foot position, I have to stand rather far in the back. 10-15cm more to the front would be nice. I extended the fuselage 7cm to the front which helped.
Because of the foot position a bit far back, I have to stand partly on the lid of the rear hatch (the one used to connect the motor cables). The round Osculati hatch was sticking out too much and not nice to stand onto. I built a custom hatch that only stands over 2mm over the board. It is also waterproof, as oposed to the Osculati. Not a big problem as the connectors are also waterproof but extra weight in the board.
Tested differen props, 3 blade FR6”, 2 blade FR 7” and Flight prop. They all work well but I prefer the flight prop, very efficient and fast.
I also built a new smaller rear wing with 187cm2.
I really like your builds. You work to a level of perfection that I’ve come to expect from myself. You’re not satisfied with anything and you’re always improving your own things. Keep it up
