1/72 688 class

[a1965l]

Ok.. based on Bob Martin's design, I modified the servo mount tray to fit my overkill servos. I also simplified it a little bit by eliminating the screw bosses that secure it to the tray. I ensured that the lower part of the mount was large enough to fit the receiver, as it seems a very convient place to mount it. Of course I do not have a picture of it... HWSNBN has a nice picture of the resin part he's pulling on his daily work thread. . It's a very simple design. I need to print another one as it needs just a bit more tweaking.. the servos are a little too loose, and the rails just a little too far apart. EZ stuff... but no more white filament. I wish someone made filament in the proper, interior green-gray that's so hard to describe but so recognizable. Anyhoo....







In all it's glory.. you can see where I trimmed the servo tray a bit to allow the servos to plug into the receiver. I'm going to have to watch for interference between servo leads and the control horn on that side. Still waiting for my double sided servo tape to show up. So here are the questions:


Top view...



Ok. I'm in the outer holes on the servo horns. The thing about rotary motion on a servo, it introduces side motion into the pushrod b/c the point on the horn which the pushrod is fixed to moves in an arc, not linearly. That's not normally an issue but here, where the pushrod has to pass through a watertight gland, that side movement seems unwelcome. I have 2 fixes, neither of which will eliminate motion, just minimize it. First is to run the pushrods to the inner hole on the servo horn. This, of course, reduces the amount of motion the pushrod can have and limits travel. The second is to turn the servos around so the output is at the front of the tray, furthest away from the bulkhead. Both of these would reduce the amount of side motion. Or is there enough flex in the glands that I'm concerned for nothing? I see the special slotted pushrods on the front servos.. important there as the servos are right at the bulkhead. Here, I have some room.


I've decided which boat to model.. USS Norfolk, SSN 714. Built local, stayed local, did it's job and brought crews home.

[He Who Shall Not Be Named]

Go for the inboard servo horn hole. Use silicon grease on those pushrods where they pass through the watertight seals.

David

[a1965l]

David, are you available tomorrow for a short block?

[He Who Shall Not Be Named]

David, are you available tomorrow for a short block?

**** yeah! What time? And what are we doing (so I can prep the shop)?

David

[a1965l]

Really, just need to pick up a couple things.. I don't have the cylinder together enough to test yet, still waiting on double sided servo tape, and thanks to your hard work last time the stern planes and rudder are in place and moving freely. I'll bring the sail, hopefully a vertical snorkle valve will fit, and other than that...

Early afternoon? 1300? I'll call before I leave, of course...

[He Who Shall Not Be Named]

Really, just need to pick up a couple things.. I don't have the cylinder together enough to test yet, still waiting on double sided servo tape, and thanks to your hard work last time the stern planes and rudder are in place and moving freely. I'll bring the sail, hopefully a vertical snorkle valve will fit, and other than that...

Early afternoon? 1300? I'll call before I leave, of course...

Yeah, we'll get that snorkel installed and working. I got servo tape for you here … no more ****ing excuses! See you later, Alligator.

Use Ellie's cell-phone, as we keep the land-line off the hook … ****ing tele-marketers!

418-0779

David

[a1965l]

Once again, I must say thanks David for your time and patience... as of today, I actually have 99% of the stuff I need to make a running boat. So, after some actual income producing work, some mowing, some tractor wrassling, and some mosquito dodging and other fun pastimes that come with owning more than few blades of grass, I found a few minutes tonight to attend to the USS Norfolk. Well, that might require some re-considering, being as there is PE of VLS tubes on the hull... can't be a flight 1 with VLS, apparently. So it may have to be the Newport News... still local.

Anyhoo.. I did some very minor soldering and then tried to stuff the engineering space into its tube. All went well and good until I reached the servos... at which point I produced 2 very nice scratches on the inside from the ends of the pushrods. Turns out the servos are just a big red c#^t hair too high. Nuts. I did like how the receiver fit under the servos, but I think that's going to have to go. I suppose I could take it out of the case, but from what I see that dosen't save very much overhead height. I think I will relocate the ESC further aft, and mount the receiver to the forward bulkhead of the metal frame. In the case. That looks like it will provide enough room for the connectors, and then there's just the matter of the motor wires to route. All simple stuff... but I'm wore out and have been at Grandpa Hellmann's cough remedy... it mixes very well with sweet tea and is good for what ails you.

[a1965l]

Raining. Let's work on the boat. Since I got the brass tube to make the stern tube with, let's do that.

I guess the first thing to do is to drill a hole. I basically eyeballed center and then stepped up bit sizes untill i reached my final size...



Looks pretty close, if I do say so myself. Ok, so the oilite bushings are a nice tight fit into the brass tube, so once it's cut to the right length, I scuffed the inside of the brass tube and cleaned it thoroughly, and then used thin CA to hold the oilite bearings in... then put it together for mark the shaft...







I have these thrust bearings... but I think they're not necessary...

Now, there is one minor issue I have to solve, and that is a jam nut for the prop. The back side of the hub is curved, and I'm not sure if the nut will hold. Now, I'm thinking about using threadlocker to hold the propellor on. Blue would do nicely, I think, and hold the prop fairly well. But I have no experience with locktite in water, so any thoughts?

Back to work.. I used a sanding drum to remove the flange from the foward bearing, and then worked the hole with a little sandpaper until l got a tight fit...
And dropped it in. I spent some time with a longer piece of rod getting it as straight as poissible, then hit the outer bearing with some thin CA just to lock it into place.





Shiney! It's not exactaly straight of course, but I'm certain it won't be an issue... note that the hub is a little larger than the aft hull. but we'll fix that down the road.

Now I know you're asking yourself how is he going to tighten the set screw on the coupling inside the hull? Well, I figure I can just snake my arm up the hull and do it in situ. Yeah right.. who am I kidding. Let's drill another hole...
cCare


Carefully and scientifically measured so it falls in the right spot....

And then mix some 30 minute and micro-balloons to fill in around the tube and lock it in place...



OK... on to the next.

[He Who Shall Not Be Named]

Get over here so we can screed that ass-end to contour with the hub. Now!

David

[a1965l]

Gonna have to be Sunday, I think, plans are being made for Saturday.

[He Who Shall Not Be Named]

Gonna have to be Sunday, I think, plans are being made for Saturday.

Sunday works for me. Bring a fresh can of Bondo, the small one.

David

[a1965l]

Been slacking. Grass to mow. Hydraulic fluid to change. Engine oil to renew. And you wonder why farmers get up at 4am....

Got in a little build time. I have all the parts on hand to close up the WTC, so let's do that. First lesson.. that damn silicone grease gets everywhere. I thought I'd just put a little smear on the O-rings, but of course it winds up all over the place, especialy wnen you're looking for that third had to stick a recaltricant wire back into place. Anyway, after a few tries and re-positioning, I wind up with this:





I'm not unhappy, but there's an issue with how the AD2 and failsafe are oriented.. the wires are touching the servo horns, and they pull very tight if you have to disassemble the cylinder. So, I went to bed on that, and when I got up in the morning with a fresh outlook, I tried this:



Turned the 2 units parallel to the long axis of the hull. I had to re-do the setup on the aD2, of course, but there's less strain on the wires, and the servo horns are clear.



Stuffed it all together and powered up:



Just have to hook up the snort line and it's ready for a water test... whoo hoo!

Now, for the next issue.. snort mounting. I had an itch to mount the valve into the sail. Means I need a disconnect in the line to it, as connecting to the actual valve would be a PITA. The issue was how to mount it so I could remove it for maintenance. Drilling a hole into the top portion of the valve was out of the question, I don't want to risk opening up the air passage in the block. So.... hot glue to the rescue! Yeah, I know, but it's generally as permanent as you want it to be, it can be removed for maintenance. So out came teh gun, I did a few dry runs to ensure clearance and that the float wasn't rubbing on the side of the sail, and....



It will clear the fairwater linkage there, it's tight enough that the float won't rotate, and it shouldn't be too difficult to hook up once the sail is on the boat. Wait.. I'll hook the hose up before I install the sail, and come up with a QD to remove the cylinder. Much easier.



I'll come up with a couple small spacers to keep it more centralized, it's actually only glued at the back to the block that holds the screw.

Allright.. it's cold outside and I'm not motivated to go out, so let me get off the computer and go see what else can be done....

[He Who Shall Not Be Named]

Good sound engineering so far. See you tomorrow. Bring Bondo and coffee!

David

[a1965l]

Morning then, or would you prefer afternoon? I'm good with either....

[He Who Shall Not Be Named]

Morning then, or would you prefer afternoon? I'm good with either....

Early afternoon works for us.

David