First time out in a hydro!

[Lights]

I got out to test my CSH today. It was the first time I ever got to drive one myself. All I can say is what a rush. When I came in after the first few laps around the lake. I was out of breath. I thought now how the hell did I get winded. I think I forgot to breath.

First run the motor was deep. I could only get 55 mph out of her. Second run after shimming the motor a quarter of an inch. I got 60.5 mph. I still have some room to come up a bit with the motor, weight to shift around and more props to test.

I also needed to change my turn fin. The first one was a standard BTM 1/8" x 7" aluminum fin It was not enough. Second fin I tried was one I made it is 1.25" longer and also 1/8" thick and aluminum. It worked great, But I just had a look at it and it is bent now. I guess I'll need to make one from SS or Titanium.

All in all I think for the first time out the hydro and myself did pretty good.

Mark

[Tom10W]

Ice Out

So the ice is out in Minnesota ehh...
Good idea to work with your fin. It is a very important part of your rig. One thing we do is check the fin to ensure it is parallel with air trap, front to back. Best way is to find a little lazer level and clamp it on the fin with the lazer pointing toward the rear. Measure in to the air trap just behind the fin and take another measurement at least 4' back towards the transom. The measurements should be equal. You do not want the fin twisted one way or the other. You can duct tape a thin shim (washer) to the fin where it bolts up to adjust the angle. It is very important to do this as a safety measure. I share this information because I don't want anyone to get hurt or hurt someone else if they $hit house on the straight away because the fin catches. I would try and get it to within 1/6" over 4' for sure. Perfect is better yet.
Good Luck and keep testing. Boat time is your friend.

Tom Kargus

[pops67g]

bulletproof fin material

Hi Mark, glad to hear about your first experience in a real raceboat. I've been racing for so long that I have totally lost touch with that "first time" feeling. If you want a fin that will really do the job, get yourself some 4130 chromoly plate. I use .125" thick for the fins on my D hydros and it is perfect. The only drawback I see for this material is the time it takes to shape one. Chromoly is so tough that it takes several hours to grind one correctly. You have to do it in many small steps to avoid heating the alloy too much at any one time. The other small thing about this material is that you can't allow it to rust, so you must beadblast and repaint these fins several times a year to maintain them properly. Have fun, Mike 67G

[Lights]

Yes the Ice went out on about the thenth of this month.ehh Sure don't need or want to take a swim yet.

Tom thanks for the info on the fin. I will make sure it is strieght with the traps today.

Oh ya see you in Burrrrrlington Tom.

Mike I have work with chromoly before. It's not bad to cut with machines and carbide. But if you were grinding it. It could be a pain in the @$$. Dad said he had some 1/8" SS I am going to give a try.

Mark

[AOFoffice]

Wow, Talk about positive news!
I sure wish we had more posts like yours. This is why some of us old folks stay with this sport, ..get new people involved and out racing.
Good luck Mark. You are like a breath of fresh air to boat racing.
Connie

[trident]

Fin

I don't recommend stainless steel for fins in the faster classes... it looks nice and works fine until you overload it, then it yields all at once. Came out of a first turn with one bent horizontal, once, in EMH. Almost went on my head. Fortunately no one was to my outside, or I'd have caused an awful crash. I'd agree with what Mike Franck said, 1/8" 4130, light coat of rustproof flat paint, blast and repaint as needed... Or, you can go for the Fred H. look, and intimidate people with that ugly rusty thing hanging out there... (not recommended). 3/16" 6061 works, too, but I prefer the thinner 4130.
Aircraft Spruce has it, if you can't find it locally.

Also, little trick to mount the fin: If you use a single pivot bolt or stud, make a backing washer out of an old Mercury clamp screw button, bigger is better, drill to suit. Use lube and a sharp drill, then deburr; these puppies are hardened. That puts the clamping force at the cim***ference of the backing washer, whereas a 'normal' washer dishes out, exerting force only in center. Clamp button supports the fin and holds your adjustment much better.

Safety first! Zero equipment failures.

[trident]

Fin

Oops! Typo! That's 'cir***ference', as in around the outside of the circle. And we all know from Geometry that a circle is a round straight line with a hole in the middle, right?

Never understood the Pi r square thing. Pie are round, cake are square (well, sometimes cake are round, too).

[Lights]

Trident I trashed the SS fin thought.

Tom I just check the fin alignment it is straight with the traps. Ruler does not read the same at turn fin and back four feet though. Because I have an inch squeeze in the traps from back of sponson to transom. It was designed that way.

[Steve Johnson]

Trident

Very nice to see Trident on this board. This man has a pleathora of Knowledge. Thank you for sharing with the general public.

[jneises]

Mark,
I have a titanium fin that you can try. Identical shape to what Mike F. is talking about. Might be worth a try before you take the time to fab one up. I also have a 6' aluminum straight edge that works grest to align the fin with the trap. Just let me know if you want to use.
Jerry

[jsilvestri]

Mark,

I use 1/4" aluminum and I have never had a problem with one of them bending on either my CSR or my CSH. The material is easy to shape and fairly inexpensive. If you decide to use stainless steel, be careful with the quality of stainless you buy. Some stainless is very tough and some is soft. I know, I bought soft stainless and made a fin out of it one time and it bent after one weekend of racing. I went right back to the 1/4" aluminum.

I'm glad you had a GREAT time your first time out!

[Fast Jack]

new math

Pie are round --- cornbread are square.

[Richard K.C. Mo.]

Agreed!!!

And no fins on hydros, Realabouts either.
RichardF

Pie are round --- cornbread are square.

[dcrummett]

Out of breath and thirsty!

Mark,

I'm only three years into this, but I still get winded and thirsty...even testing. I've told people recently driving a hydro...especially as it comes on plane...is like slipping on the ice (every time you go out!)

What a hoot... time in the boat is a lot like getting stung by a scorpion...you're truly awake the whole time but you don't swell up!!


Dan
O-49

[Lights]

Dan, Yes it is kind of like slipping on ice. But I have just one question for you. What does a guy from OK know about slipping on ice? Just kidding buddy.

Now I hope to get turning this thing right this week. I was told that I am turning this Dawecraft wrong and that is why I bent the turn fin. I have to believe this because the one that told me is a Dawecraft driver and a vary good racer.