Moebius Skipjack

[Ken_NJ]

This is for Ernie. He asked about the magnets I used to hold the sail top down. I purchased the magnets from K&J Magnetics. They are 1/4x1/4x1/32. I did not use the stock sail as I made my own. You will have to fill in the stock sail to make a mounting surface. The mount area on the sail, since it has a slight angle to it, I carved that angle out so the surface was flat so the magnets seated flat together.

https://www.kjmagnetics.com/proddetail.asp?prod=B4401

I bought my G-flex years ago, but this is what I would by today, same thing. My hardener tube is getting thick with age but still works. GREAT STUFF!
https://smile.amazon.com/WEST-SYSTEM...s%2C181&sr=8-4

[Ken_NJ]

Groton was the first time I ran the Skipjack for any significant time. I'll describe any issues that I had. Surfaced trim was good. Submerged trim, I need to remove some above the waterline foam. Submerged, the waterline is at or just below the fairwater planes. The few days before leaving for Groton I spent trimming the boat and checking out the Marlin. The seemed to be enough friction with the fairwater planes that the pushrod would separate the magnet connection. Did not have enough time to figure this out so I locked the fairwaters and hoped that boat depth adjustments can be made with the aft planes.

Saturday
Surfaced, the aft end of the boat was porpoising. I changed the sensitivity of the pitch controller from I think 3 to 1. Much better with the sensitivity at 1. Next, not sure if this is typical of a Skipjack model, going into a turn, the aft end would dig in. Will have to see how this goes once the boat is running better.
Submerged, the boat was hard to control with only the aft dive planes. Could not get it running level or have decent control. These dive planes were controlled by the knob on the top of the transmitter. Using these to control your depth and pitch seemed to not be the easy to go, even temporarily. David suggested to switch the aft dive planes to the right stick which should give better control to the aft planes. So I did this on Saturday and would test it on Sunday.
The water level of the pond was low. Where we launched the boats it was shallow and sandy. At one point the aft planes locked and would not move. A few of us could not figure out why this was. I removed one of the shafts and found a few particles sand had gotten between the fin and dive plane casing the planes to lock. Once the sand was removed all worked OK.

Sunday
Surfaced was fine.
Submerged, for me it was difficult to control the depth and have the planes keep the boat level. I’ll have to work on getting those fairwater planes working properly.
Another thing that occurred. One of the magnets that held the top of the sail down separated from its mount. I thought using G-Flex would have solved that problem but oddly it did not. Will now have to figure out how to keep those magnets attached.
Again, had a problem with sand getting in the slot in front of the dive plane. Cleaned this out once I got home.

[wlambing]

Ken,

US ships all squat when the rudder is laid over, especially at slow speed with a large rudder angle. The rudder acts like a brake and the hydrodynamic force makes the stern drop, or appear heavy. A little tweak of additional throttle will counter this and tighten up the turn considerably.

Take care,

Bill

[Ken_NJ]

Thanks Bill. I thought that something like that would be the case.

[SSN687]

Ken
Thanks for the information on the magnets and epoxy, ordered them and they just arrived this week. Those are some strong magnets for being so small.

When you completed your final trim what was your new trim weight and foam configuration? My friend is opening her pool up this week, I’m going to attempt trimming mine tomorrow.

I had the same problem (no stern plane control) while running my Blueback at Groton in 2019. The grit was between the fixed portion of the stern planes and the moveable plane. I tried sanding between the back on the stern planes and fixed portion but I wasn’t able to get enough clearance between the two to get in working correctly. After Groton I ran it my friend’s pool and had no problems with it.

Thanks
Ernie

[He Who Shall Not Be Named]

Ken
Thanks for the information on the magnets and epoxy, ordered them and they just arrived this week. Those are some strong magnets for being so small.

When you completed your final trim what was your new trim weight and foam configuration? My friend is opening her pool up this week, I’m going to attempt trimming mine tomorrow.

I had the same problem (no stern plane control) while running my Blueback at Groton in 2019. The grit was between the fixed portion of the stern planes and the moveable plane. I tried sanding between the back on the stern planes and fixed portion but I wasn’t able to get enough clearance between the two to get in working correctly. After Groton I ran it my friend’s pool and had no problems with it.

Thanks
Ernie

Of all the places I've operated, it's Groton that presents this unique problem. It's owing to the very gentil slope at the launching/retrieving point. The heavier model will be more prone to scooping up sand as it slides in and out of the water. Most other sites either have a hard bottom or sand with a steep incline. The best course of action is to shake the immersed model back and forth to dislodge any sand that gets between the stern plane leading edges and trailing edge of the horizontal stabilizers. Or, provide a wider gap between the two.

[Ken_NJ]

Prior to going to Groton I lost one of my fairwater planes. David did not have any spares and Bob is not at that point of making resin parts. I took the original Moebius parts from the kit and prepped them. Made a shaft and put notches in it for epoxy, filled the voided space on both halves and clamped together. Next day sanded. You'll see them painted up in a later post. They feel solid, no hollow sound at all when tapping on them.

On of the original resin planes, part of the fittings kit.


Prepping Moebius parts.

[Ken_NJ]

Also prior to Groton, the fairwaters had enough friction that the magnet from the servo would not hold on or move the planes, kept becoming separated. I made a small 1/16-3/32 long bearing from brass. Where the fairwaters shaft entered the sail on the inside, I use the correct size drill and hand reamed out that hole to fit this bearing. I did not go all the way thru, so the outside of the sail you do not see this bearing.



I then cut a spacer and carefully filed it down so it can be used to hold pressure against the bearings while they are being glued.



With the bearings in place, the spacer in place, the sail halves together, an alignment rod lined everything up. A few drops of CA was applied thru the bottom of the sail with a pointy thing onto the bearings on the inside of the sail to hold them in place. The sail was taken apart then a fillet of CA was added around the bearings.



The fillet of CA was then filed down to make the CA smoother. The fairwater gear as is fits exactly between the sail halves. I had to ream out the gear opening down to the set screw to accommodate the bearing. I also had to ream out a camfer so there was no binding with the CA fillet.



The new fairwater planes needed the forward part filed down so it did not interfere with the sail when at full dive or full surface.



Not shown, I also ground some flats where the set screws touch the shafts.

[Ken_NJ]

Now for the lower gear. I made another set of bearings\spacers. These do two things. They cut down on friction between plastic and brass, although the plastic gear is already loose fit on the shaft. And they center the gear on the shaft to align it with the upper gear. I made the proper length spacers. The existing plastic 'bearing' was also hand reamed to the proper size and was CA'd in place as before.



Due to all the friction, this gear bent and magnet hole elongated. This had to be fixed.




I made two brass sheets. One had a extension for a ball joint. The surfaces were roughed up, then epoxied and clamped. No more bend. I added two 1-72 machine screws just in case the epoxy gave way.







Test fit of both gears.



The magnet is gone and replaced with a ball and socket joint. Much more reliable connection. AND, after all this work, the servo to fairwaters connection works excellently! A lot less friction.

[Ken_NJ]

I wanted a third magnet at the aft end to hold the sail top on securely. My first attempt I tried to glue both magnets simultaneously. Well they came out crooked. Note to self... don't try to blindly glue two parts at the same time. They would work fine this way, but me being anal about things I removed it, then epoxied (G-flex) one of them in place. Next day epoxied the other one in place using the first one to locate the second one. I then applied a fillet along the edges of the magnets for additional holding power. The glued side of the magnets were run on like 180 grit sandpaper and the styrene surface was roughed up as well.



Much better.





To activate the navigation lights I made my own periscope. The bottom is a tube and at the bottom of the tuber is 1/2x1/16 magnet, epoxied in place.


When I insert the scope it activates a reed switch which then turns on the nav lights. Essentially and on-off switch.
Under the rectangular foam is another reed switch. The foam is attached to a float with a magnet. When the boat is surfaced, the nav lights are on. When submerged, the float rises, deactivating the nav lights.
Also when the boat submerges, the same reed switch activates a safety location LED on the deck to help locate the model should it not rise to the surface.



Hand made micro periscope from brass.



Sub beacon and periscope.

[Ken_NJ]

For the blinking submarine beacon I think I previously posted how I encase two micro LED's in epoxy. This beacon manually telescopes from the sail. To make it blink, I used two digital outputs from a Bluno Beetle. More can be found at Nicks Blinky thing thread here, https://forum.rc-sub.com/forum/gener...a-blinky-thing
Ed posted his code there, which I modified for two LED's. I used two resistors, one for each LED, soldered and shrink wrapped to the two digital outputs on the Beetle board. I made an acrylic box with lid and sealed the Beetle board in the box using silicone as a sealant. The box was placed inverted in the hull, if there was a leak, an air bubble should keep most of the water from the board.



A 7805 provides the required 5 volts to the board.


Here you can see the package taped inverted to the inside hull, the 5 volt regulator and the connector. As part of the pre-mission procedure, I brush some Corrosion-X on the connectors.



This is my code for the Beetle. With notes as I won't remember what I did.

//Programming date May 2022
//Connect Beetle to right side, forwardmost port
int ledD2=2; //Digital pin D2
int ledD3=3; //Digital pin D3
//Bluno Beetle pin reference
// D2-D5 = Programming Reference 2-5
// A0-A3 = Programming Reference A0-A3
//Operating voltage 11.1v (3s Lipo)
//7805 Voltage regulator for Beetle input voltage
//100 ohm resistor for each LED
void setup() {
pinMode(2, OUTPUT);
pinMode(3, OUTPUT);
}
void loop() {
digitalWrite(ledD2, HIGH);
digitalWrite(ledD3, HIGH);
delay(600);
digitalWrite(ledD2, LOW);
digitalWrite(ledD3, LOW);
delay(600);
digitalWrite(ledD2, HIGH);
digitalWrite(ledD3, HIGH);
delay(600);
digitalWrite(ledD2, LOW);
digitalWrite(ledD3, LOW);
delay(600);
digitalWrite(ledD2, HIGH);
digitalWrite(ledD3, HIGH);
delay(600);
digitalWrite(ledD2, LOW);
digitalWrite(ledD3, LOW);
delay(3000);
}

[Ken_NJ]

Finally for today, inside of my sail.









Today's post starts at #307 so you should scroll up and start there if you want.
Or click this... https://forum.rc-sub.com/forum/build...310#post162310

[SubDude]

This is awesome stuff Ken. The presentation is right up there with the illustrious Mr. Meriman. I have two of these kits to build (the ones I got at Subfest last year) but I can assure you that I will not go quite so detailed as you have. I humbly submit to your praiseworthy skills.

[trout]

Ken,
You really are inspiring. Love your creative thinking and the cleanliness of your installs.
How are you sealing your connections to the deck LED and beacon?

[Ken_NJ]

Thank you Steve and Tom. Your comments are most appreciative! We all have our level of skill and detailness we will go to. Steve, your large scale subs are works of art. Not something I would tackle.

For my connections between different model sections I use these waterproof connections in the first pic. I have five pairs of these to attend to. I use 2, 3 and 4 pin versions.



For the beacon LED to Beetle connection I use some PCB connections I strip from things that are getting thrown out. They are of course not waterproof so before each mission I dab Corrosion-X on it.



For the deck LED, I use this guy and do the same with Corrosion-X. If it comes down to it after time, they can get replaced.



Any exposed to water soldered connections, I smother with silicon then heat shrink it, then finger dab silicone on the ends of the heat shrink to make sure it is sealed.

That should answer more than what you asked Tom. For the benefit of all I guess.