Whiplash.

[785boats]

Not really a build, just a bit of a refit.
I bought this from a fellow club member the other day. Thanks Trev.
And thanks David for building it. Beautiful boat.
It's for Club Spec & EA Sports Hydro racing.
fitted a 9XL for now for the Club spec but will get a Leopard 2200 for the EA class.
Tested it yesterday & after a few different props the best speed on the oval course was with a back cut & slightly de tongued X645. Managed 51.5mph but i know there's more in that motor yet as the temps were all pretty good.
Handled like a dream. But there is some skipping of the tail in the turns that I couldn't get rid of. Not serious, but annoying.
Tried all the usual strut depth & angle adjustments & the rudder angle adjustments but couldn't seem to find the right combination.
Any ideas would be welcome.
If you see this David I'd love to hear your thoughts too.
Cheers.
Paul.

[Fluid]

I have no idea what usual strut depth and rudder angle adjustments you already tried, sorry. It "handles like a dream" but skips out in the corners eh? Hmmm.

There are several things to try.
- Additional weight on the prop may help. Either add some or move the pack back.
- Try moving the rudder pivot inwards slightly at the bottom, but not too much. This keeps the rudder from being a lifting surface.
- Set the strut by putting the boat on a flat surface resting on the sponsons and the strut. Adjust the strut so it lays flat on the surface.
- Try a prop which is not "back cut" This is a popular nitro/gas prop mod - which usually does little good on FE boats. It removes the trailing edge cupping on X props and can add or reduce lift a bit depending on the way it is cut.
- Make certain you have no flex in the rudder linkage. I notice a right angle bend in the wire, not a good thing as it turns the pushrod into a spring. Try to make it a straighter line from servo horn to rudder horn; use gentle bends, not abrupt ones. I hate those rubber bellows pushrod seals, they give the rod no support and promotes pushrod flexing. Run the pushrod through a length of 3/16" brass tubing running through the transom, this helps limit pushrod bending a lot.


.-

[raptor347]

What Jay said.

Also I wouldn't run a tapered rudder, I don't like them on hydros. You shouldn't need to run it as deep as you have it, 1" below the bottom of the prop should be plenty. Round the bottom so it doesn't lift.

It looks like you have a lot of angle in the strut, at least compared to how I ran mine. I ran the same strut but with only .030" under the front when sitting on a setup board.

Post a couple shots of the sponson bottoms.

[785boats]

Thanks for your responses guys.
By 'usual' I meant basically what you suggested Jay. Toe in on the rudder. Neutral strut angle, negative strut angle, positive strut angle. Battery forward & back.
Just didn't hit the right combination. Of course some of the adjustments made it run wet or too light down the straights. The other props that weren't back cut still had the same slight skipping in the corner. X440/3 X640, X642, X445. But they all ran smooth down the straights.
The handling is such that I can hold full throttle around the bends for the 5 laps even with the slight skipping.
I'll try the weight at the transom & take a bit of angle out of the strut again. Come to think of it, I don't think I tried less angle with that prop as I was running out of batteries.
All the hardware on the boat came installed. The pushrod does go through a piece of 3/16" tube in the transom. The rubber boot is attached to the tube outside the transom. So there is very little play there. And the rod is nice & thick. No give in the bends when I simulate a load on it as hard as I dare. So hopefully that's not the problem.
Brian.
I just checked the rudder & it's 1-1/4" below the 45mm prop's bottom blade. But I did notice that the bottom has been cut at a noticeable upwards angle towards the front. I'm sure this would create lift & the more toe in I added to the rudder the steeper this angle would become. I'll take the file to it to level it out & also round it off as you suggested.
I'll also see about getting a non tapered rudder.
Thanks again for your help guys. That's given me some good ideas to work with.
Cheers.
Paul.

[Scott T]

Paul, if it all gets too hard, package it up and send it to me! Easier still, I'll pick it up at the lake

Seriously, Dave had that thing motoring at the Thunder last year, so check with him exactly what settings he had for the strut, cg etc. And which prop also.

Good luck!

[785boats]

Thanks Scott.
But, Uh!Uh! you're not getting it that easily.
I'll send him a pm & see what he can tell me.
Cheers.
Paul.

[Brushless55]

I really love the looks of these hydros!

[David Kingston]

Paul

Man i miss that boat.
Its not setup correct, i can tell from the pics.
I will be back down in bris - sunday the 17th April, and also the easter sunday. I will help you get that boat setup correct.
The strut has been moved, but not much.
Forget the 9XL, put a 8XL in there, m645 set the bottom of the hull parallel to the build board or flat surface and put 1mm down angle on strut. Thats ball park, but will depend and you will need to test. There should be nothing behind the motor othen that the SERVO.
SETUP should be battery 4s, ESC than motor.
The receiver pack (if running one) and receiver will be under the STB deck where the safety loop and switch are located. There are carbon mounting plated under there.

You will need to make sure you have a good ESC when running the 8XL and that prop. I can do it on a 224MGM no worries. Things dont get warm except for the motor.

Make sure also that the prop shaft has the small drive dog on it. The big one will catch water as it passes the strut and slow it down.

Wedge rudder. Yeah - its not the best idea but i dont like the smaller parallel one as the boat can flip and i have done so in the past and bent those rudders. The taper one just has a bit more meat so it wont bend as easy.

The boat when i had it was the fasted boat on the lake for the EA class. When it goes there wont be a boat that can catch it. Just ask the boys how i got passed Mark Warren in one heat. I think we both had to change our pants after that race.

So try those small things, and definatly when im down lets get the boat going. Ive built more of these things than i can remember now.

For those who are interesed they are 33inch long. Cannot remember the beam. This one pictured is with a PTSS45 cowl and DAM ITS HOT.
Got my next one almost ready to have cowl put on.

I will reply to your PM in a bit

Regards
Dave K

[Jeepers]

so its a custom (33" long) Whiplash, nice! I like looks good with that cowl, very good!

[785boats]

Thanks for that David.
I'll certainly look forward to seeing you on the 17th. But the first race is this Sunday
& the 8Xl is in the Pursuit for Club Spec Mono on the same day. Maybe I could swap them . But as this will be my first hydro race with the guys up there I'm not expecting to win. Or even Place. Just get a feel for the boat & the racing.
The only ESC I use is the Himodel GX200A. I've never had a problem with any of them but that M645 on an 8Xl will be pulling more amps than I'm use to. I don't think they'll hold.
When you say put 1mm down angle on the strut, is that down at the rear (negative) or down at the front ( positive). I'm assuming the negative.
I can see why you miss this boat, It really is a beautiful thang.
Cheers.
Paul.

[David Kingston]

Paul

Ok with a 9XL as the only option. Wack on a M447, or x448 or something and leave everything the same, see how that goes. Should be a tad better.
High model should hold up with that setup.

I noticed there was a piece of shrink on the stuffing tube and strut. WHY?
It never got a drop of water in it when i ran it.



Paul you think that my Version 2 you have is a hoot.
I have V3 on the build table. Very nice, and i cannot wait to have it on the table. Spent heaps of time in CAD doing the mods to the plans and i have it about 95% how i want it. Few small errors which wont talke long to fix. Dream to build. I really should do a build thread of them and get people interested but im not in model boating to make money.

Any how, PM sent mate.
Talk soon.

Dave

[785boats]

Thanks Dave.
I'll give that a try.
I think a bit of water got in the boat when Trev ran it & the shrink was put on to see if that was where it was getting in. Must have worked because there was no water in it when I ran it.
And yes, a build thread of the V3 would be a good thing to see on this forum.
Cheers.
Paul.

[David Kingston]

Just reading through the post again and seen what Jay t wrote about the servo push rod and seal.

Have agree here.

Personally i like my 6mm carbon tube glued into the hull.

Then 440 pushrod soldered over that a 5/32 brass tube. This fits perfect inside the carbon tube. Forms a great seal and never has any flex. I run all my setups like this - no leaks and no flex.

dave

[785boats]

Well I filed & trimmed the rudder as suggested, set the boat up as suggested & it ran a bit better. Getting too light in the nose when heading into the wind (flipped it once) So I dropped the strut an extra millimeter. Sat a lot better.
Then I swapped out the 9Xl for an 8Xl. Started with an X642 then the x445 then the slightly de tongued X645. Gps showed 81 k/hr (50mph) on that one.
Couldn't believe how cool the temps were. 45C* on the motor, 49C* on the ESC & 49C* on the battery.
I think the X445 felt faster but didn't GPS it
Here's a bit of a video of it with the 9Xl early in the testing.

http://www.youtube.com/watch?v=JSbuY33Hx-o

Racing it for the first time today so we'll see how she goes.
Cheers.
Paul

[785boats]

Well I managed a 2nd, a DNF, & a 3rd in it's first outing, in strong winds & very rough water. So I'm pretty happy with that.
Also managed two firsts & a 2nd with the 32" Blade (Pursuit) in EA Mono.
The high attrition rate helped with all that though.
Snapped a few pics of some of the boats & people in dry dock. I'll get some on the water next time.
Cheers.
Paul.