Puffin - Trial and error engineering

[Occupant]

Think I figured most of it out(maybe)? some holes were already there but hidden under the plug on the vacuum tool. I also realized it wasn't creating a vacuum so set it deeper to allow bridging toe the exterior first to create a seal and let the vacuum do its work. on top of all that I was so close to the vacuum hose couldn't draw down much. addressed all those issues and still having more issues - namely material size so far limited to what fits in the toaster over I'm using as a heat source. going to make a insulated foam hot box powered by a heat gun (internal baffled to prevent blowing up material like a balloon) and use a full sized sheet 11x17 vs something cut to fit within a toaster oven. am I missing anything else?

FYI hole on the top is thru serves double duty 1) pull vacuum when forming 2) drill location indicator for finished canopy 3) drain hole for air/water when diving/surfacing - the cockpit is perforated to do this as well

[Subculture]

Make sure any vent to vacuum is well below any area of plastic you wish drawn tightly over the mould.

[Occupant]

Back for third attempt at vacuum forming, still not getting it hot enough - went low tech with a heat gun vs buy/build a heat source. it started to drape but not quite soft enough. Once it started draping i hit the perimeter with the heat gun until it softened and the vacuum did its magic. got most of it, not all of it and one tiny little wrinkle in it. not bad for a third try.

[Occupant]

Switching gears again (printer was down with a broken belt). Have redesigned fin to fin arm joint - reduced part count and less play - i hope! Doing so changed the linkage routing a little that snowballed into adding big clearance radius on the servo mount. so had to pot in the servos in a new mount and thought i'd share the process a bit. 1) screw servo in the mount . the mount sets the servo slightly off the bottom to allow silicone to get under and around all sides. 2) install cap on the servo 3) tape joints - there will be leaks 4) mount servo in stand - sets the cup up pure vertical 5) mix silicone 6 ) transfer silicone into mount all the way to top. at this point its observe see if you have any leaks to fix with the tape job. very slow leaks will clot for lack of a better term and self seal after a bit slowly add silicone to backfill to the top. allow to cure. 7) remove from stand 8) remove cap 9) trim flash 10) apply super lube to servo output shaft exterior 11) slide silicone washer over output shaft 12) install servo horn. the washer is another seal bridging the gap between the servo and the servo horn. the super lube keeps the washer from getting stuck to one of the faces and fils any voids within the washer once closed making it harder for air/water to intrude.

[Occupant]

Well, more fix this and break that in the process... for whatever reason my receiver had a dead channel and i use all of them so got a replacement receiver and set it up and now have lost the telemetry? after trying to trouble shoot it for an afternoon said screw that and need to get this wet and see how its doing. This morning took it out in the pool with some trim weights added (needs more to pull the body down a bit) but drive works, rudder ball doing its job. I'm seeing some thrust torque but can correct with the fins doing a little counter roll. using the fins get it to dive and progressively dives deeper faster, faster, faster then it gets deep enough to lose signal (salt system pool) and then bob back up to the surface. Then the grandson came over for science fair work and when he was leaving asked him to video my next run. i dropped it in the pool (literally, and doing so broke off the internal fin arms - ouch) but was able to get ani idea of the speed again and the rudder working. and the way the fins are fixed you can see it pull the nose under a bit in reverse. GIven i snapped the fin arms i reworked the deisgn for more material and they're working away on the printer, should be ready tomorrow. after that program ballast esc and more telemetry troubleshooting.

[Occupant]

Another pool day after printing and installing a new set of fins and fin arms. Still seeing a few issues 1) still too light, need weight to pull it under a bit more 2) See thrust torque rotating it a bit 3) once you get a little speed and hit the fins a bit it begins to dive and then just keeps getting steeper and steeper till its nose down ass up, at that point its deep enough the failsafe kicks in and it bobs back up. While I was at it printing new fins I reduced the length of the fin - how much it stuck out from the body by 25% thinking reducing the surface area would slow down the dive. the shorter fins had little effect. next going to try weighing the inputs via transmitter to make it a bit more manageable. I"ve seen the electronics to help stabilize attitude but not sure they would be appropriate here since I have two servos, one for each fin mixed to give pitch and roll - anyone have any experience with setups like this and words of wisdom? One other thing I hadn't considered till today the design is set up for the separate fins to allow controlling pitch/roll, etc to potentially make it behave like a plane underwater. what I hadn't considered is the trim weights and placement with regards to that. I still need to add weight to bring the waterline up higher on the boat, installing the new weights closer to the centerline of the boat may help, but I’m not sure if it will be enough.

[JHapprich]

Dynamic diving on speed, could that be an issiue with the hull shape itself? It looks like an inverted airplane in profile.

[Occupant]

I don't see the dynamic diving until i give it little down on the fins.

The hull is kinda Wankel rotary piston shape, with fins protruding out like an inverted Beechcraft V-tail.

[MFR1964]

Those issue's sound the same i had on my Spirou, solved the torque roll by enlarging my fins and place all heavy things as low as possible, as for balancing, the Spirou is balanced with just 1/2 inch above the surface, less force needed to dive.
Steering your fins seperatly can make things more complicated, mine are steered together with one servo.
If you intend to let her roll underwater the torque issue will stay because your boat has to be balanced with all stuff in the centerline of your boat, this is the reason torpedos have counter rotating propellors.

Manfred.

[Occupant]

For what its worth this is my WTC. The three front round legs connect to the front body. The three back legs (arrowhead shaped) connect the rear shroud. All the legs below the centerline are filled with lead to help counteract the buoyancy. It looks kinda weird but i was trying to minimalize the displaced water by conforming to internal components.

My original intent was to have the boat able to pitch and roll like a plane but with all the weight low like this not going to happen, too much too low, add to that not fast enough or enough surface area to overcome the weight. Started looking at options to get me back to that and i'm tearing up a lot of track again. started by taking volume inside the hull, shrinking it down a bit, cut outs for fin servos and arms , etc. then fed the volume and desired material and wall thickness into AI to get displaced water weight then volume for equivalent lead in cylinder forms. Put that lead on the centerline of the boat and fill in components around it so its weighted to get trim line but more neutral with respect to roll.

Also looking into using a gyro to stabilize the pitch and roll, rudder, its interesting what I've read so far. Using the Sbus to pass multi channels to gyro sounds cool. not sure about something though. a lot of gyros say they have v tail configurations but with my front fins an inverted V if i fix that orientation will i be able to have correct roll if fixed for pitch or will it be reversed?

[trout]

The v-tail mixer will work. Your using the lower portion of an x-tail and if it is backwards, many transmitters have a reverse function. Do not hold me to this, I am just wondering if this would work, If you do not have a reverse capability on your TX, you might be able to switch the red and black wires on the servo at the RX.

[Occupant]

I have the FrSky X18 and hve it mixed currently to get pitch and roll and it works great . Like i've said before once it starts diving it accelerates going down faster and faster, a gyro might help stabilize it. I have no experience with gyros and how they work. Do i pass the mixing to the gyro or just use it for stabilization? Thinking of Detrum iStone V3, would like to know for sure how it behaves before getting one. WOuld hate to get one onlu t fight new problems, make enough of those on my own. from what iv'e read this afternoon would setup like this: Have an R9 SX OTA receiver, connect channel 6 Sbus out to gyro bus in (carries all servo channels) then the gyro branches out and controls fins and rudder. use channel 1 an 2 on the rx for the ESC's 1 for drive 2 for ballast pump. figure out how to apply a v-tail cofiguration. anyone have experience and lessons learned to pass on? Meanwhile going contact sellers / company asking about my setup and how it might work or not work.