My New Mini Eco! Set up tips?

[Rich]

I just received my Mini Eco from Jim over at Minicatracing with my OSE membership discount. The boat came nicely packed with motor and servo installed. The esc came in a plastic bag with decals, instructions for the esc and boat, and a programing card. Once I was done with soldering the deans on the battery leads, I programed the esc for 3s lipo and used low timing and pwm. Programming the throttle range using my DX3S was a pain!! I had to play with the brake travel in order for the esc to recognize the neutral position. Once all was figured out I put a 3s lipo in a headed out. I had the lipo sitting in the middle of the boat up against the flood chamber wall. It was windy out and the boat handled the wake well. It did not self right and I stuffed it many many times; it came back up.

I have made a few adjustments:

1. Added a pine car lead weight to the back of the flood chamber.
2. I flipped the servo arm around so I could move the lipo back against the transom (see attached pic)
3. Added some pool noodle foam for added assurance.

The boat handles much better now and it self rights. Sometimes I have to give the throttle a quick kick for it to flip over (which can be fixed with the addition of weight and a vent hole or two on the deck).

The other problem I am having is the boat still stuffs, but only in right turns. The boat spins out on left turns. Is there anybody that can give me a few tips to remedy this? In a straight line the boat seems to be good, but I hear the prop coming out of the water a lot. Any ideas?

[martin]

Its pretty much standard to add weights on these for self righting, Most use the stick on balance weights which come in 5 & 10 grams & stick them as far to the outer edge as possible. Some put them inside the chamber & some stick them on top of the deck & place them if nessesary spread along the hull for better cg balance rather than just putting them all at the rear of the chamber. You def want to add a few holes along the chamber for water to flow in faster & air to get out. When i spoke to Tenshock about cg position they say 190mm from transom centre which is 44%, I found 175mm or 41% works much better & reduces diving but not completelly. The diving is also caused by the angled shaft with sub surface props, When you put the boat into a turn the boat banks over & the prop breaks the surface. You can hear this from the prop when it does this & the angled shaft drive line is pushing the back of the hull up & the front down & the front side thats dipping down catches the water & causes a dive. This isnt all the time as the boat turns very well in a very sharpe turn but its worse when the boats going faster in a straight line & you take a wider turn. Martin.

[martin]

One of the mods they do here in Europe on Mini Eco class boats when racing is the replace the entire propshaft assembly & replace it with something like the Etti wire drive Eco shaft assembly where the outer stuffing tube has a very gentle curve with a 1.2mm wire drive. So the prop drive angle is only 1 degree, It produces a faster more stable boat because the trust line is pushing the boat fowards & not upwards & foward as the standard drive has. You also get better handling in corners as the prop drive line isnt pushing the back up & front down. They also lower this shaft a bit to get bigger props on as stock 27mm props are very close to the hull & you cant put bigger diam props on. You also have to use a bigger rudder blade (30% bigger) on this setup to handle turning at higher speeds. It just depends on how fast you want to go re mods. Martin.

[martin]

One of the mods they do here in Europe on Mini Eco class boats when racing is the replace the entire propshaft assembly & replace it with something like the Etti wire drive Eco shaft assembly where the outer stuffing tube has a very gentle curve with a 1.2mm wire drive. So the prop drive angle is only 1 degree, It produces a faster more stable boat because the trust line is pushing the boat fowards & not upwards & foward as the standard drive has. You also get better handling in corners as the prop drive line isnt pushing the back up & front down. They also lower this shaft a bit to get bigger props on as stock 27mm props are very close to the hull & you cant put bigger diam props on. You also have to use a bigger rudder blade (30% bigger) on this setup to handle turning at higher speeds. It just depends on how fast you want to go re mods. Martin.

[Rich]

Its pretty much standard to add weights on these for self righting, Most use the stick on balance weights which come in 5 & 10 grams & stick them as far to the outer edge as possible. Some put them inside the chamber & some stick them on top of the deck & place them if nessesary spread along the hull for better cg balance rather than just putting them all at the rear of the chamber. You def want to add a few holes along the chamber for water to flow in faster & air to get out. When i spoke to Tenshock about cg position they say 190mm from transom centre which is 44%, I found 175mm or 41% works much better & reduces diving but not completelly. The diving is also caused by the angled shaft with sub surface props, When you put the boat into a turn the boat banks over & the prop breaks the surface. You can hear this from the prop when it does this & the angled shaft drive line is pushing the back of the hull up & the front down & the front side thats dipping down catches the water & causes a dive. This isnt all the time as the boat turns very well in a very sharpe turn but its worse when the boats going faster in a straight line & you take a wider turn. Martin.

Thanks for the info Martin. I took it for a spin just a little bit ago. I placed the battery a little more forward. My cg is at about 160mm from the very back edge of the hull were the seam for the two halves are. Is that the right place to measure from? I noticed that the hull likes to be a tad flighty. I also noticed that left turns the boat has never stuffed. The hull likes to hop in left turns until it gets a "grip" on the water. I am also getting this random change of direction when driving, its like the servo is glitching. Any thoughts?

[martin]

Yes cg is measured from the double seam in the centre of the hull, So furthest point back on the hull. I ran many points ranging 190mm as suggested by Tenshock down to around 155mm. I found 155-160mm to be to far back with the front riding much to high, The best position i found for the conditions i was running that time was 175mm. I think what you have to consider also that these hulls were not initialy designed for use with lipos or the extra speeds that are possible over the old ni cads or ni met hyd batteries. Martin.

[martin]

Boats never turn as well left as they do right because of the torque direction of the prop. This is why boats have most of their batteries etc to keep a bias to the left of the boat to help in turns & also to aid self righting with the flood chamber on the left as well. Most race boats are only intended to turn one way fast only using 1 turn fin set to the right of the transom to turn right. Turn fins are not used on mini eco class boats though.Martin.

[CaptPJB]

Interesting info on the Eco
Always wondered why most videos show them running anti clockwise or left while most other boats go right must have something to do with the stuffing problem going right mentioned here

[martin]

Yes the boat does dive more in fast right turns than left as the front dips in a right turn & catches the right front. I dont think it has dived much if at all in left turns. Martin.

[sailr]

It sounds like your battery is still too far back. Move it forward in 1/4" increments until you find the sweet spot! Look at the balance point on our instructions that came with the boat.

[Rich]

It sounds like your battery is still too far back. Move it forward in 1/4" increments until you find the sweet spot! Look at the balance point on our instructions that came with the boat.

I'll give that a try Sailr. How to you guys check the balance point? I mean do you just hold it with two fingers and see where she sits?

[sailr]

Yep, a finger from each hand inside the lip of the hull with the hatch off.

[SweetAccord]

It's easy to understand that a CG towards the front tends to maintain the bow down into water, increasing the wet area and hampering the planning of the boat when at speed. On the other side, a CG too close to the transom tends to raise the bow too much, making the boat unstable at speed. As a rule of thumb, CG must be between 27% and 30% of the total length of the boat, measured from transom, for a completely assembled boat - ready to run.

Everyone will try to tell you that it should be about 30% of the hull from the transom but not tell you how to figure that out. Here's how: Measure the hulls length. Multiply the hulls length by .03 and measure this point forward from the transom and mark that point on the hull. Check the hulls actual balance point with (finger method) and move the batteries for or aft to make the hull balance on that point marked. Run it and if the bow rides low and plows, move the balance point back an inch from the balance point that was marked. If the bow hops, move the batteries forward an inch.

[martin]

The 30% ish cg does not apply to these Mini Eco sub surface drive boats, I know this from extensive testing of this boat. 30% = 127mm, This is immposible to acheive moving everything right to the rear inc turning servo, rx right at the rear, battery touching transome, esc further back,stick on balance weights at rear of flood chamber. The furtest back i could get the cg was around 155mm = 36%, The boat handled terrible with the front way to high. I also spoke with Tenshock in China & asked them on cg & they said gc is 190mm which is 44%, I ran 190mm & found this to far foward & got to much diving & tried several points between 165mm & 190mm & found that 175mm = 41% worked best & reduced diving.I dont know weather its coincidence but theirs a Tenshock sticker inside the hull bottom that also has a mark on the centre of the oval sticker that is 190mm from the rear possibly an indication this is the cg point. This also looks the same area that Minicat show on their cg point details. But im sure Sailr can say more about that area that they show as theirs no measurment given on the site. Perhaps you get a measurment with the boat instrutions i dont know. But like i said the general rule of 30% + / - that we normally apply dosnt seem to work on the Eco class boats. Martin.

[sailr]

With all mini boats, the CG can be somewhat subjective. Move the battery fore and aft til you find the sweet spot and then mark it! Remember, weights of battery packs vary from brand to brand so the best spot for a 3S 2100 Hyperion may be different than with a 3S 2100 Turnigy. Also note that the higher the "C" rating of the pack, the heavier it will be.