Working up Joel's Excellent 1/72 PERMIT

[He Who Shall Not Be Named]

Mine will be the THRESHER, the first boat of the class:

[SSBN659]

Is that your new 3" Sub Driver in the first two pictures?

"Will" Rogers
SSBN659

[He Who Shall Not Be Named]

Is that your new 3" Sub Driver in the first two pictures?

"Will" Rogers
SSBN659

Naw, it's our 'standard' 3.5 SAS SD, single-motor. Identical to the one used in the 1/72 SKIPJACK.

M

[He Who Shall Not Be Named]

John Slater is in a big sweat over where to put the SAS snorkel induction mechanism in his 1/72 PERMIT. I initially blew it off, but, as it turns out, John's right to fret -- once I started sticking my version of Joel's kit together I too found it almost impossible to put a snorkel into that tiny sail and still have room for the sail plane operating mechanism and a few retractable masts. So, I was compelled to switch from the planed vertical type unit (that would have stood up within the sale) and instead employed one of my new, highly simplified, horizontal snorkel mechanisms.



I used it pretty much stock, but modified so I could sling it off the upper portion of the hull, just aft of the sail.

As is my want, I try to make all mechanisms aboard a model removable for service, modification, or replacement. So, I made some styrene mounting brackets -- the snorkel head-valve body would sandwitch between the two brackets and would secure to them with 2-56 machine screws.



The annular space within the hull, between the top of the SD and the upper hull, gave me just enough room for the snorkel float-arm to swing and assure proper closure and opening of the valve as a consequence of water level.

After gluing the two mounting brackets within the upper hull I took a page out of Tom's Good Book and also glued down a short length of styrene tube -- this to serve as a strain-relief conduit for the induction flexible hose that runs between the snorkel head-valve and SD four-point manifold.

Though located in the hull rather than the preferred position up high in the sail, the float is a bit under an inch above water level with the ballast tank half full. Half full is the typical level the tank gets before the float drops and vents the SD permitting use of outside air to finish the blow.



I was not happy with the kit provided propeller -- the blades were skewed in rake and look awful when rotating. hard to make GRP or carbon laminated propellers run true. So, I started digging around in the vaults for a suitable propeller master. Found it, a 20-something year old master used to make a tool and parts for a defense contractor customer back in The Day. The origional tool it was used to make had long ago gone sour, so I was compelled to make a fresh one. I'm using the BJB TC-5050 high-temperature silicon RTV for the tool, which will permit me to cast my propeller from white-metal.

(Pictured are just some of the propeller masters I've built over the past four decades -- some of them for movies, others for clients, some for kits, and some just for hobby use)



So I clayed up one-half of the propeller master and poured the magic-goo. Tomorrow I flip it and pour the second half of the tool. Should have bright, shiny propellers by tomorrow night.

What a slick looking boat this will be!

M

[Slats]

John Slater is in a big sweat over where to put the SAS snorkel induction mechanism in his 1/72 PERMIT. I initially blew it off, but, as it turns out, John's right to fret -- once I started sticking my version of Joel's kit together I too found it almost impossible to put a snorkel into that tiny sail

yeah no ****!

So, I was compelled to switch from the planed vertical type unit (that would have stood up within the sale) and instead employed one of my new, highly simplified, horizontal snorkel mechanisms.

[ATTACH=CONFIG]26674[/ATTACH][ATTACH=CONFIG]26675[/ATTACH][ATTACH=CONFIG]26676[/ATTACH][ATTACH=CONFIG]26677[/ATTACH][ATTACH=CONFIG]26678[/ATTACH]

I used it pretty much stock, but modified so I could sling it off the upper portion of the hull, just aft of the sail.

As is my want, I try to make all mechanisms aboard a model removable for service, modification, or replacement. So, I made some styrene mounting brackets -- the snorkel head-valve body would sandwitch between the two brackets and would secure to them with 2-56 machine screws.

[ATTACH=CONFIG]26679[/ATTACH][ATTACH=CONFIG]26680[/ATTACH]

The annular space within the hull, between the top of the SD and the upper hull, gave me just enough room for the snorkel float-arm to swing and assure proper closure and opening of the valve as a consequence of water level.

After gluing the two mounting brackets within the upper hull I took a page out of Tom's Good Book and also glued down a short length of styrene tube -- this to serve as a strain-relief conduit for the induction flexible hose that runs between the snorkel head-valve and SD four-point manifold.

Though located in the hull rather than the preferred position up high in the sail, the float is a bit under an inch above water level with the ballast tank half full. Half full is the typical level the tank gets before the float drops and vents the SD permitting use of outside air to finish the blow.

[ATTACH=CONFIG]26681[/ATTACH]

I was not happy with the kit provided propeller -- the blades were skewed in rake and look awful when rotating. hard to make GRP or carbon laminated propellers run true. So, I started digging around in the vaults for a suitable propeller master. Found it, a 20-something year old master used to make a tool and parts for a defense contractor customer back in The Day. The origional tool it was used to make had long ago gone sour, so I was compelled to make a fresh one. I'm using the BJB TC-5050 high-temperature silicon RTV for the tool, which will permit me to cast my propeller from white-metal.

(Pictured are just some of the propeller masters I've built over the past four decades -- some of them for movies, others for clients, some for kits, and some just for hobby use)

[ATTACH=CONFIG]26682[/ATTACH][ATTACH=CONFIG]26683[/ATTACH][ATTACH=CONFIG]26684[/ATTACH][ATTACH=CONFIG]26685[/ATTACH][ATTACH=CONFIG]26686[/ATTACH]

So I clayed up one-half of the propeller master and poured the magic-goo. Tomorrow I flip it and pour the second half of the tool. Should have bright, shiny propellers by tomorrow night.

What a slick looking boat this will be!

M

well done. Nice bit of mechanical engineering.

I have gone a different route. I have a pinch valve in operation via servo. Its not ideal as I much prefer a float system, but it works, seals 100%, 100% of the time. Film at 11 - provided I can pull the wife of the computer as she finalises grad school work.

[redboat219]

John,
Very much interested in your setup.
Does it still utilize the 2nd float valve?
Is the pinch servo slaved to the LPB?

[Slats]

John,
Very much interested in your setup.
Does it still utilize the 2nd float valve?
Is the pinch servo slaved to the LPB?

I'll post photos soon. I have an intermediate tube of soft fuel line silicon between two fixed points. That line runs at an angle away from one of its fixed points. The silicon tube is lassoed by a ring of brass and this is ring of brass straightens out to a long push rod that runs on top of the subdriver. This push rod connects to a motor end cap push rod via one of David's connectors. Servo activation pulls the lasso and the silicon fuel line to a point where it kinks shut. The reverse undoes the kink.
Simple, effective - but in my view rather ungainly. Much prefer the float valve and the use of kinetic force of rising and falling water.

J

[Slats]

Photos as promised here is the pinch valve that is servo activated in the Permit.




Explanation is as per the post above.
I have an intermediate tube of soft fuel line silicon between two fixed points. That line runs at an angle away from one of its fixed points. The silicon tube is lassoed by a ring of brass and this is ring of brass straightens out to a long push rod that runs on top of the subdriver. This push rod connects to a motor end cap push rod via one of David's connectors. Servo activation pulls the lasso and the silicon fuel line to a point where it kinks shut. The reverse undoes the kink.

The brass bottle in the ballast tank is the secondary safety float valve. IMO - this is the ideal place for this valve.

The system fully installed - in this position snorkel induction line is open:


In both photos above and below the brass pipe in the lower right corner connects to the snorkel via a clippard tubing line that is not connected in these photos.


Here the servo activates the push rod with the lasso aft causing the silicon line to kink and this closes the snorkel induction line. Air is now supplied to the ballast tank from the dry space:

[Slats]

Next the back end of the SD showing the connection to the push rod with the lasso

[Slats]

I should point out that the silicon fuel line has clippard line inside it at either end that mates with the brass tube fittings. This ensures a tight friction fit that will not allow the lasso push rod to force the line off either of the brass tube connection points.

As an aside...How awesome is this hobby! RC submarines to some present a world of frustration, to me they represent a world of continuous exploration and learning. If these beasts were easy I would not be in this game.

What we have here guys with this pinch valve is a compromise created due to cramped space. I must stress again, I'd rather have a float valve in the place of the servo activation. You must remember to open and close this valve, and you have in my view an ungainly mechanism that is more complicated than the float valve alternatives that David engineered from the get go. My servo activated setup is not in the territory of a Rube Goldberg Machine - but nonetheless David's float setup is mechanically much more efficient. You also are using the boat's position to enact it.

Hope this helps

John

[He Who Shall Not Be Named]

Good stuff, John. Keeps the brain juices flowing.

M

[crazygary]

Seriously "butt-kicking" engineering here, gentlemen!!
Makes me proud to be a part of this group!

Pure genius!! Kudos all around!

CG

[He Who Shall Not Be Named]

Spent most of the day working on the sail scribing -- what a pain in the butt that thing is! But, almost there. The day started with the pouring of the second half of the metal forming tool for the new propeller, with the occasional breaks to eat, take my hedius nap, and run errands for, she-who-must-be-obeyed.



The first half of the propeller tool was left to cure over-night. When I got up I pulled away the clay backing, cleaned up the master and half-tool, then reassembled the two after applying mold-release; mixed up another batch of RTV and poured the second half of the tool. I put it in the hot-box and went on to other tasks.



I finished all the lay-out work on the sail, and got to scribing again -- what a pain! Not much gel-coat on these parts so I was digging into carbon fiber. Tough stuff, I was forever grinding my scribes point on a stone. You make your pencil marks, look things over, and if their right you lay down your stencil and make the first light passes with the scratch-awl. Then you start digging in. The work is over-coated with air-dry putty and the engraved lines chased out before the goo dries. You wait, then wet sand the surface of the work, rinse it off, then work the scribe to pull out any muck stuck in the engraved lines. Prim, and examine the work ... and it looks like ****! You repeat the above steps till its perfect. Ugh!



OK, by time I was thoroughly sick of the sail scribing task enough time had passed and the other half of the propeller tool had cured. Pulling the two halves apart exposed the master which was put into safe storage ... maybe 20 more years from now, it will be needed again.

A sprue hole was punched in the tool half with the dunce-cap cavity -- this is where the molten white-metal (95% Tin, 5% Antimony) will be poured during the casting operation. The cavities and flange faces of the two tool halves were liberally powdered with talc, the excess shaken out, the tool assembled -- the two halves compressed together with some lead weights. A stand-pipe is slipped into the sprue hole -- its job to produce the pressure-head needed to insure a complete fill of the tools cavities with molten metal as the pour is quickly made. Gravity is our friend!

A previously inserted greased length of 3/16" stainless steel rod set into the lower tool would produce the bore within the cast propellers hub that later accepts the propeller shaft.

I cast three propeller. One for this model (which I'm assembling for a buddy of mine); one for another kit I'm ordering for me; and I made a third for safety ... **** happens.




I faced the forward end of the hub -- deep enough to achieve a hub base diameter equal to that of the GRP models stern. I then turned the casting around on the chuck and turned the sprue-blob to the correct dunce-cap cone shape.

This propeller is not the perfect S5W seven-blader we all know and love, but it's close -- when I made this propeller that kind of dope was still classified (more on that story later) so I had to skirt around the edges. Today, through the good works of Adam Carleson, we have the exact shape of the propeller at hand -- one of these days I'll make a proper one in 1/96 and 1/72 scale. In the meantime, I have enough crap on my plate!

M

[crazygary]

Thanks for the metal casting lesson, M!! Gotta love those BJB products!!
You make it look like a total "no-brainer"!!

Good stuff, here!

CG

[He Who Shall Not Be Named]

Do something a zillion times ... you better be good at it!

M