Tunnel Hull setup

[Doug.m]

Hello all. Thanks for adding me to the fourm and happy new year to all.
I’ve been into rc for awhile. Surface vehicles only. I’ve always wanted to build a boat since I was a kid so its time. I purchased two used 3.5 k&b outboards and a 29” boat hull. Not sure on make of model of hull. My intention is to build a Tunnel Hull for the outboards. At first the plan was to get the engines running and keep with nitro. I’ve had nitro cars before so it’s nothing new to me. I got the motors running but now I’m thinking about going to brushless. Nitro is great when it’s tuned right but it’s getting it tuned right is a pain. I’m thinking on keeping the kit length around 24 to 29 inches. I’m looking at the vs1 or the Dumas hot shot kits. My question is on the electric side. I would like to run a single 3s lipo so I’m thinking a 90 to 120 amp esc and a mid 2,000 Kv motor.
I’m not racing just want something to run while I’m at the lake. Looking to run around the 40’s mph . Would love to hear some ideas on this thanks.

[JestDanny]

Happy new year and welcome to the forum. I play with both the Dumas HS Sprint and the AquaCraft VS1. Both are great fun little boats. The Dumas hull is shorter and wider, its tunnel is also 1/32 shallower than the VS1, = hull turns right as well as left and handles great, but you NEED flat like glass water for best results. The VS1, longer, narrower and deeper tunnel is better when the water is less than flat, also the VS1 is more oval racer, the cowling center is offset so it turns better right than left. The VS1 will need more mods to the hull than the Dumas to run brushless elect power. At the end of the day both boats give very similar performance when running similar set ups. My Hot Shot Sprint on 3s runs mid 30's, on 4s it gets real fun with that little boat runnin mid/upper 40's. Three things important when tuning a tunnel boat set up, center line of prop shaft ride height, thrust angle of prop shaft, hulls center of gravity, get those right you'll have a fun, good handling play toy. I run my Dumas on 3 or 4s and my VS1 on 5 or 6s(un tested on 6)

Here is my set up for the Dumas Sprint, motor AquaCraft UL1 2030 kv. atop a K&B lower, Seaking 120 amp ESC, batt = 4s 5000mah 50c, top speed 46 mph on a Prather stainless 215 prop. The K&B lower is bullet proof jest keep the shaft well greased, the draw back is with the K&B you are limited to a max of 42 mm prop dia, an O. S. lower you can run larger dia props and gain a mph or two.

[Doug.m]

Thanks for the info. I'm leaning towards the Dumas kit.The biggest issue i will have is mounting the motor outdrive to the hull. I'm hoping the kit comes with some sort of instruction on this.

[JestDanny]

Using the K&B lower you will want to use an adjustable outboard mount. Prather or Du-bro don't matter both do same job, I use the Prather mount. Find center on transom, find vertical, motor needs to be centered and vertical on transom for best handling, set the height of your mount so centerline prop shaft is in line with sponson bottom, so you have equal adjustment up or down from that point, its not so hard. If you can get a 120 amp ESC and a motor that can handle 4s, start out on 3s have fun get the boat dialed in, later if you want, its just a matter of dropping in a 4s an go faster.

[Doug.m]

Next time your working on your Dumas could you post some pics of how your battery and electronics are laid out. And did you put any foam or some type of flotation in yours.

[JestDanny]

Flotation, YES, I cut squares of Styrofoam and put it in every space in both sponsons and tunnel deck. Sorry no pictures of the electronics lay out, I striped the boat down for winter make over two weeks ago, going to re do the elects lay out. I originally had the steering servo in the front compartment all alone. The battery was in the middle, the rx and ESC were in the rear compartment, I sealed them with Plexiglas and radio box tape, drilling holes for wires and cooling lines, sealing those with silicone.

[Doug.m]

Thanks for the info. I'm waiting for tower hobbies to get the kit back in stock so I've been looking at pics trying to figure where everything will go.

[Insanity Plea]

Checkout the the flycolor 150 esc, you can pick them up on eBay for $40. I've ran them pretty hard with success.

[rol243]

yes the Flycolor 150 esc,s are becoming more expensive i have noticed going by Bang Good Trading they were around the $50 mark and now the $70 mark. popular item.

[Doug.m]

Funny you bring that up. I had a Amazon gift card and I bought a 120 amp flycolor esc. Jus got it yesterday. It looks like it's built well.

[Doug.m]

I also ordered a goolrc 3660 2600kv motor. I plan on running 3s battery so if my math is right that should put me around 28,000 to 29,000 rpm's. I'm a little worried if I'll have enough torque.

[Insanity Plea]

yes the Flycolor 150 esc,s are becoming more expensive i have noticed going by Bang Good Trading they were around the $50 mark and now the $70 mark. popular item.

$36.06
https://www.ebay.com/p/Hot-Flycolor-...d=142122275340

[Doug.m]

I decided to go with the vs1 kit. Tower hobbies had one in scratch n dent section. Said cowl is off center which from what I've seen and read it's supposed to be. They had it mark down to $112 and I got another $10 off of that. So $102 plus free shipping. I think I did ok.

[JestDanny]

Fine choice good boat. The biggest issue with converting a 3.5 nitro hull to FE is getting the battery far enough forward to catch the correct balance point. VS1 = 29.50" CoG = 1/3 hull length = roughly 9.5" should do.

[Doug.m]

Thanks again for the info. What do you think about a 3660 2600kv motor running on 3s to start out with.

[JestDanny]

Not sure of that motor but rpm's seem ok. If it can spin a X440 prop that should put it in the mid 30's, good starting point.

[Doug.m]

It’s a cheap motor. I’m not throwing a lot of money at it to start. Once I get a running boat and get used to it I’ll upgrade.