Revell Type VII Build advice

[He Who Shall Not Be Named]

Andrew,

Here the servo you need, http://www.sub-driver.com/electronics/micro-servo.html Caswell carries it. No, water is not the issue. Likely, as you suggested, it was tugging on the servo lead. When you pull the servo, unscrew the case, and look to see if you pull one of the three lead wires off the PC board.

[Avera]

Hi David,

You mentioned removing the pushrod and servo as one unit. Just to be clear, are you referring to taking out the pushrod or unhook the servo once I remove the mounting band?

If it is the former then I was thinking that it would be tricky trying to insert the short push rod in the tube. To make it easier, I would make a new longer pushrod insert that into the bulkhead and as I push it through I would snipe off the unwanted length as it passes through the drain hole. I have a micro wire cutter that should fit through the drain hole.

The other method would be to do what Trout did and that is to try to hook the servo to the existing pushrod then attach the mounting band (a dozen tries or more???). Not sure which would be easier and safer to do (chance of a leak with a new pushrod).

If the screws were made from steel a small magnet attached to the screw driver would hold the screw in place.

Andrew

[He Who Shall Not Be Named]

You're over-thinking this. Just do it!

David

[Avera]

Got the parts and installed the new servo. Left the pull rod in place, just removed/replaced the servo. Works perfectly, although it took two installs as I had inverted the pull rod hook to the servo arm which caused the servo to pop out of the brass bracket. I took apart the old servo and noticed that where the top casing of the servo clamps down on the lead wires the insulation on orange wire is broken exposing the wire strand which appears to be cut. This I suspect created the intermittent short and depending on how the wiring is tugged, would allow the servo to work or not. Not sure how the wires got cut, perhaps during the manufacturer and possibly by me tugging on the wires every time I took apart the electronics.

Had to go to my LHS to buy a micro Phillips screw driver with a long handle to reach those little screws. Tried doing it with a shorter one, most frustrating. The longer screwdriver made a big difference. I also noticed that the holes for them goes through the bulkhead into the ballast tank. Possible source of a future leak??? Hopefully this weekend I will have another sea trial in the Tub of Tranquility.

Andrew

[He Who Shall Not Be Named]

Slather the 2-56 machine screw threads with RTV sealant/adhesive before you screw them into the after ballast bulkhead. Duh!

David

[Avera]

Duh is right, I didn't notice that until I had screwed them in and was checking for fit and movement. I will probably take it apart again and add the sealant. Could probably add sealant from the backside (have access to them from the drain hole).

[He Who Shall Not Be Named]

No, no. You don't have to do that. Just as you suggested at the end of you post: put a dab of RTV on it and slip the rod through the after flood-drain hole in the bottom of the ballast tank and apply the dab of RT over the screw holes on the wet face of the after ballast bulkhead.

David

[Avera]

Thanks and will do as suggested, but your reply was a bit late as I had taken several shots of a single blend Scotch in anticipation my next course of action. Could have saved (and enjoyed better) the Scotch for a less stressing contemplation. Oh well, next time I'll wait a bit longer.

On a more serious note, perhaps in the future instead of the Phillip head screws you can use Allen head bolts of similar size. This would make it easier to install/remove. I use them on my slot cars to secure the motor to the chassis as well as to secure the deck of my RC Blue Devil destroyer.

[He Who Shall Not Be Named]

You know ... that last bit, about using Allen screws for those long, hard to reach places. I never thought of that! Good stuff. I'll see if my supplier can get those in. Good thinking there. That would make such work a whole lot easier. Now ... where's that Scotch!

David

[Avera]

BTW, I also got the waterproof switch. I presume that goes into that little pocket in the bow cap of the SD. What size drill bit are you using?

Also, in an effort to loose some weight and streamline the electronics I am planning wiring directly the electronic side to the battery wire (with a little bit of length to fully expose the components), eliminate the ESC switch, and eliminate the T connectors on both ends. The battery side already has a built-in connector with the JST plugs. Currently I am using two 7.4v 1100mAh batteries in parallel. To lower the weight, I was going to use 1 battery and install the switch to minimize the time current is being drawn before the boat gets into the water. Right now once I seal the SD, the power is on, no external on/off switch; bit of a pain.

I want to use a smaller guage battery wire (the wire traveling between WT compartments) than the one included with the SD as it is very stiff and can easily jam the ballast servo arm when the electronics are installed. The smaller guage wire idea came from the wiring for my lipo batteries which appear to be around two guages smaller than the connecting wire. To me it makes sense to use a similar guage wire since the distance is short and not a lot of amperage is being drawn (not racing the motors).

Any suggestions or comments?

[He Who Shall Not Be Named]

1/4" Bit.

Device idle current is next to nothing, the real pull is from the propulsion motors. But, a switch makes life easier.

Weight is not the issue, displacement is. A normal load-out of devices within the SD produces a total weight that is easily compensated for with displacing foam in the saddles and other portions of the hull. Don't hard-wire any more than you have to! Makes life a ***** when it comes time to trouble-shoot and swap out stuff.



22-Gauge power cable is fine here. Shorting the ESC switch wires is a good move -- saves much room.

David

[Avera]

Getting closer. Did another trim test; bow floats nicely, the stern still sinks but overall the boat floats slightly above waterline with empty ballast with the stern supported by hand. Removed a bit more keel weight and added foam from/to the stern area and a little weight to the port forward side to offset a right tilt. Need to let the RTV dry. Discovered another two builder errors. 1) I placed the snorkel part (air intake/fill) too close to the fill stem on the SD so I cannot attached the air can to fill the ballast. Will need some sort of extension. 2) The magnetic cross members to mount the deck to the hull are too short from earlier sanding. The hull top opening is a little wider now (probably due to the numerous openings I have done) than in the beginning so those parts easily detach.

Dave is it possible to get/purchase another set of the those five resin parts plus magnets?

Hope to test the trim again tomorrow before I go on vacation.

Andrew

[He Who Shall Not Be Named]

I'll fix you up, Andrew. E-mail me a list of what's needed along with your mailing address.

David

[vital.spark]

Andrew,

you can fix the cross members by CA gluing a bit of white styrene on to them. I had a similar problem as with the ballast weights in place the hull spread apart slightly.

Myron

[Avera]

Hi Myron,

I had already tried that and it works as a temporary solution, but you need to add the styrene to both sides to keep the magnet properly aligned. I rather start anew.

Thanks

Andrew