Skid Fin Material

[propnuts]

Safety

It's been my experience that if you want a dumb rule passed attach safety to the wording and you'll stand a pretty good chance. Let me bolt a steel skid fin to my car mirror and drive by and whack you at 65MPH, then we'll try an equal strength aluminum one. If you tell me you can feel a difference, then maybe this isn't such a bad idea. The proposal also mentioned cost, but I bet I can spend just as much on an aluminum fin, if I HAVE too.

[99R]

Hahahah well said. Tony maybe I can hook you up with a steel one if you want? Jimi O doesnt get one.

[T Chance]

Spray can of aluminum paint???

[Merc1]

General safety

It's been my experience that if you want a dumb rule passed attach safety to the wording and you'll stand a pretty good chance. Let me bolt a steel skid fin to my car mirror and drive by and whack you at 65MPH, then we'll try an equal strength aluminum one. If you tell me you can feel a difference, then maybe this isn't such a bad idea. The proposal also mentioned cost, but I bet I can spend just as much on an aluminum fin, if I HAVE too.

Now that's funny! But on a serious note, If someone wants to improve on ones safety while racing maybe we should be looking into the equipment we wear! The Kevlar certainly helps but it is not as good as it could be. How about adapting some formed flak material to the sleeves and upper thighs of the pants. Kinda like hockey equipment. Just a little added protection helps, Remember this is RACING! It is DANGEROUS!

[bill van steenwyk]

3:09 post by Propnuts

In the several years I have been looking and participating on this web site, this is one of the most intelligent and thoughtful statements made. IMHO.

BUT since this is APBA meeting time it will be interesting to see what comes from the various commissions in the "name of safety" In the past, as everybody surely now knows, "safety rules" have been a way to bypass the memberships wishes. I think if you were to look at this type of rule made the last 10 years, even though some have been made with good intentions, unintended consequenses have resulted, of various types, and not always good. Then of course, there are those passed as part of someones personal agenda. I see the use of radios is on the PRO Commission agenda again this year. That should be interesting.

[hydroplay]

Tensile strength isn't as important as modulus. Tensile strength points to amount of stress it takes to permanently deform. Most of us- except Jack- operate with lower stresses than that. Higher is better of course. But more important is the stiffness to limit the deflection that will occur with stresses less than the maximum. These lower stress will deflect the fin but when released the material will go back to it original position- elastic deformation. I certainly don't want the fin to permanently bend but I want to limit the flexing as well. Stiffness and ultimate strength are not the same qualities.

[alanaker]

Not true

Hydroplay - Most of what you posted is true, but...Modulus is pretty much the same for all stainless steels,and mild or alloy steels - just under 30 million PSI, but "bendability" varies tremendously depending on alloy and heat treat condition. Same for Aluminum, modulus is around 10 million PSI but strength varies wildly depending on alloy and heat treat condition.

[Lights]

I don't care what material you guy's are pissing about. It will take one hell of a hit to shear any of these materials from front to back.(the direction it tracks) Side load shear is a hole other story. Move on, as long as we need side fins the only safe side fin would be a vary flexible rubber one.

Mark

[Matt Dagostino]

Rockwell Hardened Steel!!!!

Sam may not remember(he is getting old) but in 1983 he made my brother Greg Kneeland a rockwell hardened steel fin for his B&H CSH since Greg drove the sh** out of the boat with a Merc 30H and constantly bent any fin Sam configured........until he came up with the steel hardened fin. I am now using the same fin today with a brass cotter pin on my 20ssh so the fin will kick up if i hit a good piece of debris!!

It looks like the carbon fiber fins Sam is selling with his new boats don't bend but they are fragile in terms of chipping easily along the leading edge..........

Later

[hydroplay]

Yes we made a bunch of fins at one time out of 4130 chromemoly steel and had them all heat treated and some were hard chrome plated for durability. I always left mine ordinary rusty steel just to look like it was a left over piece of junk. They wouldn't bend under Wienandt's EMH and Palmquist still has at least one old one and a new one for his championship-winning FEH.

I got away from the steel ones for several reasons. They are hard to keep perfectly flat during the heat treat. They take longer to cut out and grind the leading edge. They are heavier. Thicknesses are limited and its too much hassle to get ground to special thicknesses. All these issues are eliminated with CF or CF/glass fins plus they look racy. They are a hassle to make as the CF is exceedingly hard on saw blades and dulls them quickly and the dust is so itchy it makes fiberglass dust seem like ordinary sawdust but the end product is really nice.

But Matt is right, for all their stiffness and strength, the CF blades and subject to nicks and gouges fairly easily. But they are easily resharpened by simple sanding.

[Trihedral_1]

Hahahah well said. Tony maybe I can hook you up with a steel one if you want? Jimi O doesnt get one.

I have one, and it's a good one. That's why I proposed the whole fin "thing".

I just thought a rule like this would make things a little safer for the drivers, keep some racing costs down, and give a new guy or gal one less thing to worry about. It’s under Safety Rules because that’s where fins are currently addressed in the rulebook.

No hidden agenda, no grudges, no loopholes, no big brother, no harm no foul, etc…

I did learn that if you write something down and send it in, that people at APBA read it, and it could actually end up on the SO agenda.

Jimi O (305R)

[Dick Tyndall]

Carbon fiber turn fins............

Sam may not remember(he is getting old) but in 1983 he made my brother Greg Kneeland a rockwell hardened steel fin for his B&H CSH since Greg drove the sh** out of the boat with a Merc 30H and constantly bent any fin Sam configured........until he came up with the steel hardened fin. I am now using the same fin today with a brass cotter pin on my 20ssh so the fin will kick up if i hit a good piece of debris!!

It looks like the carbon fiber fins Sam is selling with his new boats don't bend but they are fragile in terms of chipping easily along the leading edge..........

Later

A chipped edge or a gash in a carbon fiber fin can easily be repaired with cyanoacrylate glue ( "super" glue ) and micro ballons ( or baking soda ). A little bit of Scotch tape helps sometimes, too. When the glue dries, you can sand the fin back to it's original shape. On carbon fiber fins I have made I have sealed the outer edges with this glue and sealed the entire finished fin with a coat of CPES epoxy.
I also mount fins to their brackets with a single bolt/nut/washer that is snugged just enough so that you can move the fin by hand. I also use a 1/4-20 brass round head screw as a "breakaway" screw, usually about 1 1/2" from the pivot of the big bolt. Saw a slot in the screw end of the brass bolt, in case if the fin does get kicked up, you can use a small screwdriver and get the brass screw out of your bracket. I do many turn fins for R/C boats this way. A kicked-up fin is easier to fix than repairing a torn out sponson........

[Corin_Huke]

Reinforced cockpit sides

I have read with interest the ongoing discussion regarding fin materials and designs. I have to say that this is not a debate we have ever had this side of the pond

As James (Aderholdt) rightly says, there have been few (if any) serious incidents that have been as a direct result of fins. Have we simply been lucky? - possibly. I would moreover put it down to the fact that the majority of our hydro classes have adopted the UIM rules relating to reinforced cockpit sides. With the recent change announced by the UIM, this will mean that 100% of our hydro classes will have adopted these rules and safety measures; from OSY, 0-125 through to 0-500, 0-700 (the latter using safety capsules)

The adoption of reinforced cockpit sides is by no means a 'cure all' approach. However, when combined with other safety measures, kevlar cut suits and possibly changes to fin design, I personally believe it is worthy of very serious consideration and would urge you to do so

There are some boat builders in Europe that have adopted an approach of a fin that flips up in the result of an impact. See photo below from a Dickfors of Sweden design of boat. A small diameter brass bolt is placed in the hole towards the rear of the bracket in. This bolt shears in the event of any impact and the fin can then flip up. Okay, it can be a pain if you hit some floating debris in the water and this pops the fin up, but I would rather this happen than the fin stay in place in the event of an impact with another boat, for example

[hydroplay]

I don't know what the big deal is with making some shear pin or other gizmo for the fin besides the clamping bolt. One bolt is more the adequate to hold the fin to the bracket. We only used one bolt on our 20/CSH rig last season as well as our championship winning CMH and Form E hydro rigs. There isn't that much load on the fin trying to pull it back unless you've got one an inch thick or so. Back in the days we ran speedometer pinkups with thicker pitot tubes hanging well below the bottom, they were only held on with a couple #8 wood screws.

I have used two bolts in the past, one above the other but that was to allow some experimenting in shimming one or the other to camber or decamber the fin. We learned what we needed and have gone back to just a single bolt.

[ryan_4z]

I don't know what the big deal is with making some shear pin or other gizmo for the fin besides the clamping bolt. One bolt is more the adequate to hold the fin to the bracket. We only used one bolt on our 20/CSH rig last season as well as our championship winning CMH and Form E hydro rigs. There isn't that much load on the fin trying to pull it back unless you've got one an inch thick or so. Back in the days we ran speedometer pinkups with thicker pitot tubes hanging well below the bottom, they were only held on with a couple #8 wood screws.

I have used two bolts in the past, one above the other but that was to allow some experimenting in shimming one or the other to camber or decamber the fin. We learned what we needed and have gone back to just a single bolt.

We always use one bolt as well. I don't need two bolts, I can barely keep track of one.