Building my first inboard hydro

[btbm007]

Hey all long time forum viewer first time poster. So I grew up racing full size outboard kneeler hydros and have always had some sort of o/b tunnel r/c usually powered with a k&b 3.5/7.5 for running around after the big boats were done but I decided that this winter I wanted to build a inboard hydro to play with so I ordered up a ML Boatworks gp310 since I have already built one of his o/b tunnels and o/b kneeler and they went together pretty smooth and were pretty durable. Since this is my first inboard I dont really know what all running gear I need to finish it or how to choose the mounting position for the motor, shaft, strut, and rudder. Also need tips on the best motor and esc setups to look into. I want to make it legal for P-Limited just incase I happen to make it out to one of local clubs races but it will mostly be used at the local pond or at the lake after the big boat races. All help is much appreciated and Thanks in advance.

[Bande1]

I have a modded k&b .21 inboard with pipe for sale. If you insist on FE be aware it only last about 120 seconds at a race pace (+/- 55mph)

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[btbm007]

I was going to go nitro but all but 1 of my current boats are nitro and im looking to build something that I can just plug in and tear up some laps................. also a lot of the people around the local pond only put up with the sound of the nitros for a tank or 2 before they start yelling lol

[Bande1]

ok so the best motors and esc is a castle hydra xlx2 and a probably a Tenshock 2240 motor in the 2050kv option. SMC HLC-HP 2s 6500mah packs OR 2 smaller 4000mah (approx) 4s packs wired in parallel. That is the tip top setup. You can run a a raider 150A with a proboat 3831 motor of and go a few mph slower for 1/5th the cost.

ABC props are chronically sold out on OSE so I would get a prop from Alan Elzer or BAM racing on facebook, Bob English on intlwaters, Mark Shouland on intlwaters. OR you can get a 4416 and 4616 OSE brass prop. (you should get at least 2 props). IMO Octura props work great on hydros M645. Octura and prather props are "old school" and high lifting props due to their shallow rake angles. ABC props have high rake 17 or 19 degrees but you can adjust the strut to account for either.

to find where to mount everything try to find some pics of complete boats to work off of. You want the boat to balance around the turn fin. usually in rear of it but that varies from hull to hull. some want a balance point way behind the turn fin. you can always move batteries fore or aft to dial that in. Also I like to mount motors, servos with E6000 clear because you can heat it up with a hot air gun and remove the glue. while still being strong enough to secure everything. That way if you make a mistake you can reverse it. you can always add epoxy over top later if you want the extra security.

the easiest shaft system is a .150 flexshaft with a 3/16 stub shaft. as for rudder you can chose any .21 size. cheap 95mm ones on amazon for $10 work just fine. TFL, speedmaster is the good stuff but probably $50. single water cooling is fine also. Turn fin just get a mojo racing sport 20 fin.

for servos I use Miuzei red 20kg ones from amazon. Top tier servos from pro modeller if you want to be elite. Servo mounts a lot people make there own from a block of cherry or pine on each side of the servo and a strap across the top.

[btbm007]

Awesome, thankyou for the info, I have a rather large prop box that is full of different props that I picked up on craigslist with a pile of .21 outboards and a graupner tunnel hull and I figure ill probably have a few props in there that should work hopefully. Are people still running watercooled lipos or watercooled battery trays? the first time I ever went to check out a club race everyone one there was saying that those were a must have but that was also probably 10ish years ago

[Peter A]

In my GP 310 I run a Tenshock 2240 2050 kv (P-ltd legal), OSE Raider 150 esc, Turnigy Graphene 6000 mah batts. I used to have a TP4050 2050 kv in it. Props are usually Dr Props 642/3, 447,sometimes 445 if the water is really rough. It is a reliable setup that runs around 60 mph all day. I could go faster but it is a relatively small boat and the faster you go, the quicker you are upside down!
I have held our club P open trophy for several years, mostly running this boat, sometimes my Cyberstorm.
If I was going to do a new boat I would go with either the bigger 338 or the new Whip 20.

[btbm007]

Thanks for the info Peter, I was just looking at the Tenshocks but still have yet to pull the trigger until I have the hull all together. How do you determine your rough motor position and rudder positioning? All ive ever done are o/b tunnels which are basically center on transom and center on depth of the tunnel so im still trying to understand all the alignment and weight distribution on these boats so that I can build one that handles at least half decent lol. I just finished framing up the sponsons tonight so now im just waiting for my carbon cloth to show up so I can start sealing them up.

[Peter A]

Here's some pics. I can take some more for you if you need.

20200509_161354.jpg 20200410_155030.jpg 20200509_161518.jpg

[btbm007]

Any pictures you have would be awesome to have for reference. Hopefully going to have the sponsons ready for glass and epoxy tomorrow night and then start on the center section. Ill try and get some pics of it tomorrow before I lay down the epoxy.