Waterproofing Hull

[Max-Q]

End goal is to waterproof M41 hull. Battery box cover will be glued/sealed in place. Cut top of batt box off to maintain molded-in ribs/rigidity. Frankly, the hull seems pretty stiff as-is. However, I see many reinforce the hull w/various aluminum shapes. Would it be better to remove the batt box completely and add side-to-side stiffeners? Are lengthwise stiffeners attached to two side-to-side stiffeners recommended? FWIW, added will be red-motors gearbox and Visiton FRS7 speaker. May do metal turret ring. Has all-metal tracks, wheels, idlers, sprockets. Metal shocks will be installed. Has 360-degree turret. Power will be Lipo batt. TIA, Dave

[RichJohnson]

None of that work is needed. Unless you intend to drive it in water. Then maybe do the water proofing but the rest is a worthless venture that is not needed at all.

[Max-Q]

Running in shallow water is likely. I'd feel better knowing the bottom half or so of the hull is waterproof. On the fence re stiffening. Would like to hear from others on this. Might build a simple back yard course which would involve varied terrain from dry and dusty to lush green and a few structures to destroy!

[SoCalBobS]

If you keep the top and bottom hulls screwed together, there is no need for stiffeners under normal "abuse".

[Max-U52]

If you keep the top and bottom hulls screwed together, there is no need for stiffeners under normal "abuse".

Agreed. They're kinda like a uni-body car when they're buttoned up. Most guys only add bracing if the upper is held by magnets.

And there's another waterproofing option for shallow use, just waterproof the electronics. The motors are fine and will actually run underwater, so a small tupperware or custom made and sealed box big enough to hold the mfu. Lots of silicon sealer at the holes where the wires pass through and you can get away with fording rivers, but I don't think I'd try to go full submersible.

[tank_me]

I run magnets to hold my uppers to lowers and upper turret to lower turret on most of my tanks. It really depends on the model as to what I've done to stiffen it. I tend to remove the battery boxes, seal up the bottom, and then I will poor resin in the bottom. Is it necessary...probably not. The resin has several functions for me. It does help keep the bottom from twisting, it makes a nice level floor to mount stuff to, and it adds weight. It's a tank and I like weight...some don't. I personally don't like my tanks bouncing around and I feel like the extra weight helps mitigate that for me. I also like the chassis opened up because I typically install larger speakers in a bigger enclosure with aftermarket MFUs.

Weight leads to lower battery life, but I use 18650 based Li-Ion batteries. I have yet to run one dry in an event, but I also don't run smokers.

On my HL ZTZ-99 I did add some angle aluminum because I use magnets and the upper hull was pretty wavy. The long nature of the hull with all the metal wheels, suspension, tracks, etc also had a part in that. Part of that was due to the age of the tank. My original ZTZ-99 had the older 27mhz system in it so it hadn't benefitted from any of the running changes HL has done to their tanks over the years.

I braced my M60 because there were sections of the hull that looked like they were bowing in and those sections would bow regardless of being screwed together.

Being that I also tend to battle most of my tanks, I like the ability to remove the upper fast as I've had to make quick field repairs or adjustments.

So in the end, I evaluate each one of my tanks that I build to meet my customization needs. It's up to you and what you want.

[Max-Q]

tank_me...when I first saw your resin method, I felt that was a bit over the top. To prevent bouncing, that makes sense - and is the my reason for adding metal. Makes more sense when using magnets as I will be doing to access battery vs external charge plug. I've been tempted to try resin on other projects so this may be the one. What type/brand resin was used? Any suggestions? How thick was the resin base? Off to the rabbit hole!!! BTW, I too like a nice clean installation.

[Max-Q]

When using resin, how do you mount things? Drill and tap? Double-sided foam tape? Install threaded insert into resin before it sets?

[tank_me]

Well, it's not my resin idea. Others did it before me. Any generic clear two part epoxy resin works like this one:

https://www.amazon.com/Crystal-Bubble-Yellowing-Coating-Casting/dp/B0CX5BKNK5/ref=sr_1_15_sspa?crid=1APTZB79IMKJ8&dib=eyJ2IjoiMSJ9.JDLKBzSg0-0RM2r_kx-yaFHqWhXFzYhK6OQXFsWH4GFBvruuOR-uzwl6RVWJccagsJakF6TffA_3jYpZ1JhAVmltzeR3_9yoKRkF9rradLUkyrWoAp-5za57-uZ3Ei_Fs6HwBBFJ_6Dv_fM_lpc8gtyomRr2mVJWhmMj72dTqoYKaZRn0lSg2rSkW1yiMGXMe1ee9nWE8WPKWCq5HB35TKkmMyNgUfGOlRva1bRgLMxI6ZGbBnPsZ83HtR_QDa4eEGIxQERuXF4wOYjW-75xJs0EIu87UGfFfRJoshOT278.S_gm0c4gcemP5dqopcj3NQQf4b0AzwaeIsrglfJJf5E&dib_tag=se&keywords=clear%2Bresin&qid=1719179887&s=industrial&sprefix=clear%2Bresin%2Cindustrial%2C115&sr=1-15-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9tdGY&th=1

I prefer the ones that mix 50/50 as they are easier to measure. One part of the resin will be thicker and the other thinner. It's easier to pour the thinner one into the thicker one when mixing. I will typically use a hot glue gun to seal all around any area the resin could leak out of as if there is even the tinniest pinhole, the resin will leak out. A lot of folks use tape to seal the battery compartment...that's great if you like to leak resin. Hot glue around the battery compartment seal on the bottom works great. I just use a chisel blade hobby knife to remove the glue after. I will also seal any holes for power switches with a glued in styrene cover plate or you can hot glue the plate over it. If using the resin on a tank using the standard torsion spring type suspension, I seal the holes in the back of the suspension that protruded through the hull with hot glue. That ensures nothing leaks out and the hot glue won't be seen through the resin once it cures. It also makes the torsion springs easily removable. Nothing like having to clean up suspension arms where resin has leaked out on them. Ask me how I know. Just ensure that the hull is straight and level while it's curing as it self-levels. Bubbles aren't really an issue because this is a tank and not jewelry and most of them pop on their own. Once mixed, the resin is kinda the consistency of cake batter. Takes about 4-6oz of resin per chassis. Only larger tanks like an Abrams or ZTZ would need 6oz. It's typically closer to 4oz and it's better to err on the side of less as you can always mix more to pour over what has already been poured. I think it ends up being less than 1/4" of resin in the bottom. Above all, make sure you put it over something like newspaper or a tray to catch any resin if it does leak. If not you will have a nice mess to clean up... :) Just follow the directions on the resin closely and they typically work very well. I let the chassis cure for at least 24hrs before messing with it again.

I know I've poured resin in my Bulldog, Pershing, T-72, ZTZ-99, and my SU-76i (PZ3 chassis).

[tank_me]

When using resin, how do you mount things? Drill and tap? Double-sided foam tape? Install threaded insert into resin before it sets?

You can drill and tap resin if you like, just don't inhale the dust. I like to use Velcro personally so that I can remove stuff for maintenance and troubleshooting. I've never tried a threaded insert into it, but you would have to find a way to secure it from moving for the 24hr cure time and ensure no resin got under it or it would just fill up the center. Might be easier to install an insert after by drilling a hole. Using a soldering iron with an resin insert adapter might work with some resin depending on it's temperature resistance, but once again it wouldn't be good to inhale the fumes from that.

[tank_me]

I use like the 2" wide Velcro that comes on a roll. It's super sticky and allows you to move stuff around in case something doesn't fit quite right once the upper hull is on. It holds my batteries in place aggressively. I used to get all fancy and make hard mounts for stuff placing everything just so, but I abandoned that thinking after having to rebuild mounting locations that didn't fit right.

[sclui56]

I use like the 2" wide Velcro that comes on a roll. It's super sticky and allows you to move stuff around in case something doesn't fit quite right once the upper hull is on. It holds my batteries in place aggressively. I used to get all fancy and make hard mounts for stuff placing everything just so, but I abandoned that thinking after having to rebuild mounting locations that didn't fit right.

Oh no, I understand why you changed, but I recall watching some of your builds on the "other" form and thought they looked great as nearly everything was properly positioned and laid out, they were very neat and took good planning!

[Max-Q]

VERY informative! Thanks tank_me!!!