So Cool Zooma!!!!

My Kopy Kommander was pictured in action at our Southport Club Open Day this week by a visiting member of the Bury Metro Model Boat Club.

Thanks for the picture Ken - that is a great action shot 👍

Photo credit Ken Mears.

Sunday 24th August 2025.

After much testing with various battery locations I have decided to revert back the the original placement - because the boat actually drives (sails?) so much better with them mounted on either side of the motor.

When mounted on either side under the cockpit, the boat did not feel as stable and it did not “ride” as well.

With only one battery placed across the back of the compartment under the cockpit the boat felt even less stable and felt as if it needed some ballast adding to the front to help it “sit” down in the water better.

No battery position affected the hulls action of wanting to “dig-in” at the bows or attempting to “dive” when turning sharply at speed into choppy water or a large wake, so this is a characteristic of the boat that I am happy to live with.

….. but I have previously made some adjustable trim tabs for use on a really fast boat that I used with some success that have given me some “food for thought” ….but I am not so sure that they would look “right” on a Sea Commander……….

I came to the same conclusion as yourself Chris - the Sea Commander was never designed to run quite as fast as I am running the Kopy Kommander - but I have seen videos of Sea Commander’s (and Sea Queens) being driven at unrealistically high speeds and they appear to be running very well.

Maybe they also dig in at the bows if turned violently?….or maybe because they don’t have any strakes they just side slide and don’t dig-in ?

The fact that the Sea Commander comes with a “wave deflector” in the design kind of suggests that the boat is handling exactly as it is designed and expected to do?

The natural buoyancy of the hull will never allow it to actually go completely under-water (like the ED Krack-A -Long was designed to do) and when the water is deflected over the decks and front cabin it does look very impressive. I could imagine a real ocean going boat handling in same way in rough seas ?

This in turn makes me wonder why the larger version of the same boat (Sea Queen) does not have a wave deflector.

I have a Sea Queen to restore - and I think I will add a wave deflector to it - because it looks “right” and I have witnessed it working well on my Kopy Kommander.

You don't think you're being too harsh on the poor old girl do you Bob! I know the Rapier is performing exceptionally but with the KK you are asking it to do things it was never designed for and in a similar full-sized boat, scalewise, you would never be travelling at such high speeds and executing sharp turns under power.

In the video you showed earlier it looked to be running nicely and at a scalelike speed. I know you are a bit of a speedfreak though! 😀

Funnily enough when undertaking lake trials with the Huntsman 28 a few weeks ago I had some occasions when the boat dug in on tight turns into choppy water. I can only guess that the water was getting above the chine rail and pushing the bow down or grabbing it? I don't really want to do too much to it though as the boat sits nicely on the water and I can't really move the battery any further back, though I could add some ballast though. Anyway I will finish the build and see how it performs again. I'm not too worried as I know about it and will just drive it accordingly.

Test conclusions?

There are no definitive conclusions to be had just yet as it was still possible for me to cause the boat to attempt a dive into the water with the LiPo’s mounted in any configuration.

As it stands, the Kopy Kommander can be turned violently at speed into its own wake or into a choppy water surface to cause it to “dig-in”

This happens quite suddenly as the boat can be seen to be planing along at speed looking very secure and stable and shrugging-off the conditions easily - but a sharp turn at speed can cause the bows to dive down into the water rather than continuing to ride above it.

The Kopy Kommander was tested today with the LiPo batteries moved back from being held in custom made “holsters” on either side of the motor into the compartment behind the engine bay under the cockpit.

For this test the power lead from the ESC was re-made and threaded through a pair of holes that were bored into the bulkhead that seperated the engine bay and the cockpit areas.

As this was only a test the LiPos were secured with Velcro strips to the bottom of the hull inside the cockpit.

It was quickly noted that the boat raised up onto the plane even faster that it did previously and my “observer” claimed that the boat was quicker too!

The boat did not feel as “stable” as it did previously and gave me the feeling that it was resting on top of the water rather than travelling through it.


A second test only had one LiPo cell in the cockpit section and one returned to the engine bay, with one cell on each side of the hull.

This configuration felt very strange as if the boat wanted to corkscrew its way along in a twisted motion.

The final test saw only one LiPo being carried, and this was mounted across the rear of the cockpit floor, and in this format the boat felt a little more unstable - like it needed to carry a little more ballast to help it sit “in” the water rather than being sat on the top of it!

The two hard cases LiPo batteries have been moved back in the hull and are now in the next compartment under the cockpit.

I carry two batteries side by side, but I nearly always run with just the one connected.

Having one battery on each side means that the unused one acts as a counterweight for the other.

If a boat needs to carry any ballast, I like it to be useful (if possible) and not just “dead weight”, and by laying a battery on each side of the keel, I also get the weight as low as possible.

Today I will be performance testing the hull to see if the rearward shift of the batteries has stopped the boat wanting to dive when under power on choppy water following a sharp high speed turn.

I have left enough wire to also carry just the one battery across the rear of the cockpit floor, so that is another test that can be completed easily this morning to see what works best - and to find out if carrying less ballast has any improvement or detrimental effect on the boat’s performance and handling.

When I compared the Kopy Kommander alongside my Rapier the revised battery position makes a lot of sense.

I am not sure why I didn’t position them under the cockpit (as I usually do on my classic model power boats)in the first place, but at the time I liked the idea of housing the motor, ESC and batteries together in the “engine room”, but this has probably given a too far forward centre of gravity.

The overall size of the LesRo Rapier compared to the Kopy Kommander is interesting, but the approximate proportions are about the same, so the relocated position of the battery weight should help to balance the boat in a similar way.

The Rapier battery retaining method is shown in the picture on the left.

I may devise something like this for the Kopy Kommander as the “retaining strap” secures the batteries firmly, but is easy to unscrew and remove thanks to the threaded insert secured in the central divider.

Following my worrying experience with the Kopy Kommander on choppy waters last weekend where it wanted to dive under power following tight fast turning manoeuvres I have decided to relocate the two 7600mah 2C LiPo cells to change the balance of the boat.

The picture on the left shows the boat as it is now with the LiPo batteries slotted into their “sockets”, one either side of the motor.

My plan is to move them back and out of the engine compartment and into the next rearward compartment under the cockpit floor.

This will move the balance of the boat more towardss the stern in the hope that this will prevent the boat’s desire to dig its bows into the water under certain conditions.

The second picture shows the two cells in their proposed position under the cockpit floor.