Cat designs for scratch builders

[Eodman]

Jeff, when you go to BTM Marines site their boat sure looks like the boat that MHZ USA is selling as a Skater.

[befu]

bottom tripping

Your quite right about the higher deadrise running deeper for a given speed being why they turn better, the deeper inside flat side of the inside sponson acts like a long shallow turn fin on a hydro, however they also tend to be narrow with not enough stability to turn as well as they can, also being scale models of the current offshore cats they don't have much or any anti-trip angle on the outside of the sponsons like the yellow one in post 31.

So on rolling it is not the deadrise with a lack of a pad, it is as mentioned the scale narrowness <sp?> of the hull. also, you mention the trip angle? Is that the high deadrise portion of the hull to keep the top spray rail from digging in? Kinda like the one shown here on BBY's new cat? (hope they do not mind a little free advertisement of thier boat by reposting)

Seems like for a RC boat you could do a 12 degree deadrise for water handling and then the last portion at 24 degrees to prevent tripping. With a spray rail and 2 strakes, inner two sections at 12, outter at 24?

[RandyatBBY]

I have been reading the thread and enjoying it. Ya thanks for the plug, I do need al the help I can get. I have been thinking about putting on a strake on the side of the sponson to deflect the waer just like the SC26. Keep up the good work guys! Wish I had mot time to read more of the threads.

[domwilson]

It looks like I should have posted all my dimensions here too... oh well. Anyway, my 22" scratch cat (dimensions on two other posts) has a dead rise of 12.5deg. With the scale ride pads in the plans, she had moderately ok turning abilities (its been a while and this was my FIRST scratch cat build almost two years ago). Since I added the 1/8" x 1 1/4" ride pads to the existing ones, she corners great - you can see the 3-4 deg resulting deadrise; much more sliding and less flipping. I would even venture to say speeds are greater and overall stability greater. The torque roll vanished too. oooo, I may have to add these pads to my micro 14" cat....

Here is a set of bulkheads and the stringer I digitized from the shockerman plans. all dimensions are 1:1. I could send someone a pdf of this - it was too big and had to render to make it upload. these plans can be scaled to any size!! Even 1/2 scale and we all go for a ride!!

Jesse, you have a PM.

[Eodman]

Jeff-when I went back and re read the description on MHZ's website they are in fact referring to as a MTI Skater so I don't know what its called or whose design --- but I do know I like the look and hardware designed for it!

[Jeff Wohlt]

I think they realize people identify with Skater. Just more marketing junk.

I have always wanted the small version. It owuld be a ripper on 3S and a little outrunner.

[Jesse J]

Dom, sent you your email. Enjoy
J

[domwilson]

Dom, sent you your email. Enjoy
J

Thank you. Replied to your email.

[NativePaul]

The red line here is the anti trip angle, during a turn when the at least the rear of the boat is sliding sideways the anti trip angle on the freeboard will give lift keeping the sponson on the waters surface, without it the outside sponson can dig in which trips up the boat resulting in a roll.



The pad and high deadrise sponson design has huge antitrip built into the high deadrise portion and raises the freeboard higher above the water surface making the anti trip much less important, but still a good idea especially in rough water as the penalty's (extra hull weight and higher aero drag from the increased frontal area) are microscopic as so little extra hull is needed for it with this design.



I was thinking about the hydro turn fin analogy I made yesterday and how much hook you would need on the turn fin to keep the inside sponson down if anyone made a hydro with 3.7:1 length to width rather than the more usual 1.5-2:1 when I thought that angling the inside of the sponsons of a cat may have the same effect and keep the inside sponson of a narrow cat down stopping it rolling, obviously the extra downforce would scrub off some speed during the turns so it still wouldn't be as good as a wide cat but a narrow cat slowing down in the turns without lifting off would be a hell of an improvement over rolling on its back when a high speed turn is attempted, has anyone ever tried this?

[Jesse J]

Funny you mention the turn fin concept. Ever since I owned a mean machine, I have been thinking about incorporating this in my plans. In fact, you will see a subtle black line in my post with the plans (#30). I like the idea and next one will have some of this action. I suspect it is part of the great success in the turnability in the MM. I WILL be trying this.

[Jeff Wohlt]

The formual tunnel hulls are a good design. Granted they trim down fast for corners but it is the sharp edges on the inside of the MM that makes it turn well but also the width of the boat...hard to flip it over.

The difference is do you want to slide thru a corner more and have more control or be a tunnel hull and make hard hairpins like the formula1 s? For our boats I want some some slide because hard cuts scrub speed big time! No if you just want to turn on a dime then you are knocking your speed off greatly.

[Jesse J]

Sliding round the corners is pretty dang fun!! good point, who needs hairpin turns anyway? I guess it comes down to do you want indy car handling or touring car handling... drifting is a blast!

[ODIE105]

MYSTIC C5000 plans/bulkheads

Does any one have or know where I can get the plans/bulkheads for the mystic c5000 or something close to it. I am new to scratch building and I need all the help I can get

[Jesse J]

Does any one have or know where I can get the plans/bulkheads for the mystic c5000 or something close to it. I am new to scratch building and I need all the help I can get

not sure what you mean; I have the plans for the red and yellow boat I posted pics of, just pm me with the size and I can send them to you.
J

[lomdel]

Does any one have or know where I can get the plans/bulkheads for the mystic c5000 or something close to it. I am new to scratch building and I need all the help I can get

From me...