Twin out-board cat discussion

[F1 madness]

just want to get peoples opinion on this,im thinking of building a twin out-board Cat,this will be designed and scratch built by myself this is what iv come with:
hull 40"long x 13"wide x6"high to keep a low sleek looking hull.
(1/4 marine grade ply & 2mm,3mm Lite-ply)
2 x OS outboard legs
2 x Scorpion 4025,1100kv,6s,2200watts,100amp
2 x 200amp ESC
2 x metal geared hi-torque servo,running twin links to each Ob and linked together
2 x 47mm 3 blade props L/R
4 x 5000,30C+,3s.2 running in parallel to each motor
What you reckon,iv started drawing it up and hopeing to start build shortly LOL

[F1 madness]

This is what im aiming for
Hull:
http://i577.photobucket.com/albums/ss219/retic79/F1%20boats/MONO%20RC%20BOATS/Rc%20offshore%20catamarans/dualcat.jpg
OS leg:
http://i577.photobucket.com/albums/ss219/retic79/Miscellanious/Osleg.jpg
Scorpion HK4025,1100kv:
http://i577.photobucket.com/albums/ss219/retic79/Miscellanious/Hk40251100kv.jpg

[F1 madness]

Doing abit more research LOL
what about this set up:
2 x OS outboard legs
2 x Scorpion 4025,890kv,8s,2700watts,95amp
2 x 200amp ESC
2 x metal geared hi-torque servo,running twin links to each Ob and linked together
2 x 51mm 2 blade props L/R
4 x 5000,30C+,4s.2 running in parallel to each motor
which option do you think would be better

[ozzie-crawl]

hey daz,have you looked at the REK lowers,not as nice looking as the OS but composite so both would probably weigh less than one OS, probably cost less to buy 2 reks than one os as well.
just a thought as there would be a lot of weight in the a$$ end
lol just looked at the size 40", should be ok with that power having a bit of weight,check prop size as most legs are limited to prop with the cav plate on

[F1 madness]

hey daz,have you looked at the REK lowers,not as nice looking as the OS but composite so both would probably weigh less than one OS, probably cost less to buy 2 reks than one os as well.
just a thought as there would be a lot of weight in the a$$ end
lol just looked at the size 40", should be ok with that power having a bit of weight,check prop size as most legs are limited to prop with the cav plate on

Alrite bud
i have looked at the rek legs,but with the size of the hull and weight,just thought they be abit stronger.
im either not gonna run cav plate or will make a spacer for it as it screws on so not to worried about that part.
i will also install water pick ups in the sponsons,so wont matter if i run with or without :thumbup:

[steveo]

might want to use inrunner motors because of the wet location

[j.m.]

Outrunners would be better since they would shed any water more easily than an inrunner trapping the water inside the can.

[F1 madness]

Cheers bud,but will be running outrunners,i know a couple others who run outrunners on outboards with no trouble.

[ozzie-crawl]

yea out runners are great on tunnels,bit of a spray with wd40 at the end of the day to flush them out and there done

[F1 madness]

yea out runners are great on tunnels,bit of a spray with wd40 at the end of the day to flush them out and there done

sorted,which option do you think would be best buddy,you always give sound advice and i trust you:thumbup:

[ozzie-crawl]

first of dont listen to my dribble,its a lot safer :blah::blah:
i tend towards high volts lower amps if it can be done. just check that the scorpion motors in the larger sizes bolt patten will fit the standard adapter on the lower leg (25mm) also the motor shaft needs to be 5mm i think as the square ended flex couplers are for 5mm shafts
i would look at twin cats around the same size and see what power there using
as in watts,shoot for some thing similar.
i think 6s with twins would be nice,hopefully doby mite chime in as i think he had a fair size scorpion in a cat,he may have more idea on there power out put and if a out board would handle the power

[F1 madness]

first of dont listen to my dribble,its a lot safer :blah::blah:
i tend towards high volts lower amps if it can be done. just check that the scorpion motors in the larger sizes bolt patten will fit the standard adapter on the lower leg (25mm) also the motor shaft needs to be 5mm i think as the square ended flex couplers are for 5mm shafts
i would look at twin cats around the same size and see what power there using
as in watts,shoot for some thing similar.
i think 6s with twins would be nice,hopefully doby mite chime in as i think he had a fair size scorpion in a cat,he may have more idea on there power out put and if a out board would handle the power

Already checked bud: 5mm shaft,25mm hole spacing,thats why i chose these
http://www.scorpionsystem.com/files/i1,199_full_dimension.pdf
I have looked at a couple,but most seem to run singles,but did find this
http://www.rcgroups.com/forums/showthread.php?t=1043673

[ozzie-crawl]

i havent looked at the big scorps for awhile couldnt remember.
i remember that blue cat,still got pics on my computer of it.
mite be worth sending the guy a pm

[ozzie-crawl]

for got to add he is a member on here and knows his stuff

[F1 madness]

i havent looked at the big scorps for awhile couldnt remember.
i remember that blue cat,still got pics on my computer of it.
mite be worth sending the guy a pm

might do that actually,see your full of bright ideas:doh:

[F1 madness]

most of my good ideas are in the off topic section (skippies and kiwis)
check the last 3-4 pages youll see what i mean :banana:

ill have a butchers now:thumbup1:

[K.R.Joye]

I think outrunners would do great on O/Bs.They are so hard to cool(properly) inside a boat Couple of things, i would suggest using counter rotating motors just to offset the torque moment givin off by the outrunners also run 3/16 cables. Last, your going to need some good 150-200 amp ESCs, meaning don't go with Hi-Models. Etti 150s should do the job for 6S. Keep us posted!

[F1 madness]

Thanks bud,so you reckon go with the 1100 kv on 6s,should be able to modify the out boards for 3/16 flexis.
Also what do you reckon to the overall size.

[K.R.Joye]

Thing is you can run big props with outrunners, I would say maybe up to a 450 with 4025/1100s. You maybe be ok with .150 cable considering you will probably be running count/rotating motors with 447R&Ls.

A 40" Cat hull should handle the 2P weight, besides you will need the ballast to keep from flipping backwards on starts.

[F1 madness]

Sorted im just starting the drawings now for parts needed to start putting it together,i think this is gonna be a fun and interesting build,and my biggest 1 yet LOL
will keep you posted on progress :thumbup:

[Fluid]

I run a Scorpion 4025/6 on 6S and it needs a lot more prop than an x447, even in a single motor 35" cat application. I know you want to run counter-rotating props, but you won't like the low speed from the x447s. Mine runs well on an x455, but if you want more than 45-50 mph you'll need either more pitch or more motor.

These motors are rated by Scorpion at 100 amps tops. I've run mine in the 130s and it doesn't get too hot, and in an OB application it may work okay. But remember that these motors are designed to run in an open helicopter and drawing over 100 amps continuous may shorten their life - or not.



.

[F1 madness]

[QUOTE=Fluid;208671]I run a Scorpion 4025/6 on 6S and it needs a lot more prop than an x447, even in a single motor 35" cat application. I know you want to run counter-rotating props, but you won't like the low speed from the x447s. Mine runs well on an x455, but if you want more than 45-50 mph you'll need either more pitch or more motor.

These motors are rated by Scorpion at 100 amps tops. I've run mine in the 130s and it doesn't get too hot, and in an OB application it may work okay. But remember that these motors are designed to run in an open helicopter and drawing over 100 amps continuous may shorten their life - or not.

Cheers bud,which motors and props would you go for then if i wanted hit min 50mph

[BakedMopar]

I am not familiar with the O.S. lower unit but the K&B stub shaft doesn't allow for props with larger hubs (447's and up). Is there a way to lengthen the stub?

Edit sorry I meant OS lower unit.

[F1 madness]

I am not familiar with the O.S. lower unit but the K&B stub shaft doesn't allow for props with larger hubs (447's and up). Is there a way to lengthen the stub?

Edit sorry I meant OS lower unit.

not sure,if i cant get that size prop on the stub that come with the unit ill have some machined at my local engineers,whose a friend of mine,nothing is impossible

[BakedMopar]

Don't take it the wrong way. I was asking cause I would like to run a bigger prop on mine. I'm sure anything is possible if you have the resources.

[F1 madness]

Don't take it the wrong way. I was asking cause I would like to run a bigger prop on mine. I'm sure anything is possible if you have the resources.

not taken wrong way,whats the biggest prop you can get on the standard shaft.
(how long is the hub is the max)

[BakedMopar]

I can only get a 445 on. The 447 and up has a longer hub and I can't get the whole nut on. Not too sure inexact measurements but I can gt them for you later if you need.

[F1 madness]

I can only get a 445 on. The 447 and up has a longer hub and I can't get the whole nut on. Not too sure inexact measurements but I can gt them for you later if you need.

that would be a big help cheers bud,iv got some cf props the 42mm,45mm,47mm, all have the same length hub LOL

[Darin Jordan]

I can only get a 445 on. The 447 and up has a longer hub and I can't get the whole nut on. Not too sure inexact measurements but I can gt them for you later if you need.

If you replace the stub shaft assembly with one from Hyperformance Products, you'll have plenty of length, and a stub that will last a LOT longer than the standard K&B:

http://hyperprod.bizhosting.com/psa35.html


Cool project.... I'm going to be doing a dual outboard conversion on a ProBoat Miss Geico later this summer, but I'll be using dual ProBoat Stiletto Outboards on it with dual BlackJack or Stiletto power systems... Should be a fun project!

[BakedMopar]

Thank you very much for the info Darin! I use my outboard on my rescue boat and I would love to use a 447/3 on it.

[Darin Jordan]

Thank you very much for the info Darin! I use my outboard on my rescue boat and I would love to use a 447/3 on it.

No problem... that stub has about 1/4" or so more length. 447 should fit without any trouble.

[F1 madness]

If you replace the stub shaft assembly with one from Hyperformance Products, you'll have plenty of length, and a stub that will last a LOT longer than the standard K&B:

http://hyperprod.bizhosting.com/psa35.html


Cool project.... I'm going to be doing a dual outboard conversion on a ProBoat Miss Geico later this summer, but I'll be using dual ProBoat Stiletto Outboards on it with dual BlackJack or Stiletto power systems... Should be a fun project!

Alrite Darin,i look forward to seeing your version with awesome looking outboards,and the geico.
Im looking forward to start the actual build,but for now its just working all the measurments out,im pretty sure i can get it to look very simular to the 1 in the pic,but with my own touches (hopefully LOL)
Will keep posting with updates maybe even a few pics once drawn up.

[DPeterson]

Awsome guy's. Looking forward to more pictures of dual outboard cats. Here's mine for some inspiration. Ran it this past weekend. I have a lot of work to do. All it did was porpuse. Could not get it on plane. When I hit the throttle it wanted to flip sideways. Probably will have to convert to counter rotation. I think too I had it way over propped.

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[F1 madness]

Awsome guy's. Looking forward to more pictures of dual outboard cats. Here's mine for some inspiration. Ran it this past weekend. I have a lot of work to do. All it did was porpuse. Could not get it on plane. When I hit the throttle it wanted to flip sideways. Probably will have to convert to counter rotation. I think too I had it way over propped.

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Man thats cool,what outboards you using on that they look ace.
Hope you get it sorted be sure to get a couple of vids,be interesting to see it go

[Darin Jordan]

Awsome guy's. Looking forward to more pictures of dual outboard cats. Here's mine for some inspiration. Ran it this past weekend. I have a lot of work to do. All it did was porpuse. Could not get it on plane. When I hit the throttle it wanted to flip sideways. Probably will have to convert to counter rotation. I think too I had it way over propped.

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Doug,

On an OPC, when you raise up the outboards, it actually causes the nose of the boat to raise up (loosens up the front of the boat).

Might need to play with the outboard height. I'd keep the neutral, but adjust the prop depth and see if lowering it helps.

How does it balance out, by the way? Got any shots of the inside?

[Eodman]

Yup raise the height on the transom not the angle or tilt from the transom! Is that a toysport jolly if it is did it come with the extra part in the tunnel? Mr Toth came up with the part to help with the porpoising!

[Eodman]

If you go on Aqua Crafts site and look at their EP1 outboard - they have a pdf of the owners manual and in it - it shows a good starting spot for placement of the outboard on a transom!

[Eodman]

I'm using the Hi-Performance 3.5 lower leg kit that Steven sells here on his site and I picked up a couple of 1700 kv brushless out runners from South River RC to try. These motors are the red ones on his site and if I remember right were $39 bucks a piece! So if it doesn't work I'm not out alot of money!

[F1 madness]

I wanted to use these legs (bullet drive),but was having difficulty finding dimentions needed,so settled for the OS leg.

[F1 madness]

Heres a quick drawing of the outline of the hull,side on view,all i got to do now is draw up the all the parts then get some board and start transfering it to that.
http://i577.photobucket.com/albums/ss219/retic79/Miscellanious/DSC00025-1.jpg

[F1 madness]

LOL do you reckon a pair of these would work:
http://i577.photobucket.com/albums/ss219/retic79/Miscellanious/bigboy.jpg
Just kidding

[DPeterson]

F1 Madness

Man thats cool,what outboards you using on that they look ace.
The outboards are KMB gear drives. Went with these cause I had them and I was looking for extreme scale.

Darin

Might need to play with the outboard height. I'd keep the neutral, but adjust the prop depth and see if lowering it helps.

How does it balance out, by the way? Got any shots of the inside?
I built it without the adjustable plates as I only had one of them. Critical mistake I think. CG is close to 30%.

Eodam

Is that a toysport jolly if it is did it come with the extra part in the tunnel? Mr Toth came up with the part to help with the porpoising!
Yes the Toysport Jollycat. Never seen a better quality built hull. What is this extra part you speak of? Thanks for advice on the auquacraft site.

I am going to focus first on getting one the outboards set up for counter rotation. Then see what happens. Will probably order another jack plate.

Doug

[ozzie-crawl]

think he means the tunnel extension

[F1 madness]

Well hopefully,i may have some new outboard legs to try,completely new not even on the market,but if all goes well they maybe,they should be more suitable for big power brushless motors 3/16 flexi and stubshaft,and be able to run upto 60mm props with cavitation plate tith water pick up,they have 12* angle change and 12mm height adjustment,will accept any motor with hole spacing up to 30mm.once i have 1 will post some pics,these will hopefully be available in cast alloy,or carbon poly.
Will keep you posted

[Eodman]

do a search for eodman oanmd then jolly magic part! yes it is the extension!

[Rumdog]

Definately make the drives counter rotating. If not, It will torque over to the starboard side extremely bad.

[F1 madness]

Definately make the drives counter rotating. If not, It will torque over to the starboard side extremely bad.

yeah they will be counter rotating,will try it bothways to see which is best and more stable.
Going to pick up some boards on tuesday so i can start the build,should be a fun 1 thats for sure

[timjz]

Awsome guy's. Looking forward to more pictures of dual outboard cats. Here's mine for some inspiration. Ran it this past weekend. I have a lot of work to do. All it did was porpuse. Could not get it on plane. When I hit the throttle it wanted to flip sideways. Probably will have to convert to counter rotation. I think too I had it way over propped.

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That looks really cool, how long is that hull? How do you like the geared lowers? Any inside shots?

[F1 madness]

just got back from picking up some more materials to start the build,so gotta carry on drawing out the bulkheads etc and start cutting them all out.
Im really looking forward to this 1:bounce: