One for debate!

[Grimracer]

One for debate!

Tunnel Racers

At a race not all that long ago one of the tunnel boats running had a turn fin mounted on the side of the sponson. This turn fin could be viewed from looking above the boat.

Now I know that I have seen this in the past and I also know that records have been set with this set up.

The IMBPA (not sure about NAMBA or APBA) says nothing about the location of the turn fin.

Question is should it?

What are your thoughts.

Thanks..

P.S. Lets keep this civil.

Michael "Grimracer" Zaborowski

IMPBA Outboard Director

 

[Slideblues]

Well far be it for me ta hold back

For SAW I could see how a outside mounted turn fin could be necessary due to the reduced deadrise angles. But for Oval I just dont think it is needed.

Just my opnion,

Gene ;D

 

[MarkScott]

Since I'm not a "racer", does my opinion count? But I'll add my .02¢ anyway. If it's not in the books, then it must be legal.. Well, at least not illegal... Thinking of NASCAR type rules where they bend them as much as possible.

For me, tunnels, Sport 40 and 1/8 scale are about the only classes that appear to be like real race boats. Sorry DV fans, haven't seen many full scale race boats that use surface drives lately. I would think that an attempt to keep the tunnels in scale with the full scale racers should be done. But, then again, only 1/8 scale has wording that the boat must look like a real boat that has raced.

So, should they be allowed be on IMBPA race boats, well, I'd say no.

Mark.

OB Nut Racing: I'm just a NUT...

 

[Bob Kensill]

I know that we don't like to "name names" but you are talking about Dave's Leecraft. Two things that I will say about this. First,if you have your boat set up right you will not need a turnfin on any tunnel hull. I started racing full-size tunnels in 1968 and only saw a fin on one boat ever. My Nova tunnel will turn right on the buoys at full throttle. Second, that turnfin sure made short work of that Villian,didn't it. LOL(sorry about that) I don't think that you can start regulating turnfins on tunnels because they are defined as hydros in the IMPBA rule book.

Bob

 

[topfuel443]

Due to the design of a tunnel boat, I say no it shouldnt be allowed on the outside of a sponson. The inside edge of the spoon is what real tunnels rely on for turning capabilities. It sounds as if the "added" turn fin is just a bandaid for a poorly built/setup boat. If you so choose to put one on the inside edge of a tunnel sponson then so be it, it would just be adding to the effect of the already present innner edge. I dont know if it would be an advantage though, turn fins have LOTS of hydrodynamic drag anywhere they are placed. If you dont beleive it, take the turn fin off of any rigger and you will see a speed increase, sometimes significant ........(you just wont be able to turn ;D )

What is your take on it, Oh Great Outboard Director??

~ James

 

[Jerry Dunlap]

I agree with the rule interpertation, "If it doesn't say you cann't, then you can."

When we first began running model tunnel boats turn fins mounted to the inside right sponson wall were universal. A few guys back then began mounting them to the outside of the sponson. The outside fin mounting worked well. Obviously, there is no speed increase resulting from a turn fin. It is a handling and control improvement.

However, with developments in sponson dihederal the boats were able to corner without a turnfin. The tunnel boats I currently race corner fine. I don't need a turn fin to assist me in drving inside the corner buoys. I can do that just fine, thank you.

JD

 

[user 115]

I don't see a problem with it.. Another well regarded tunnel in D4 has trim tabs.. Does that make it a mono?

Only problem is that boat cornered like it was on rails. Have to get back to the drawing board and figure out how to catch it..

Another question.. How about Keeley Turbo Heads on 21 Sport O/B Tunnels? Rules don't say you can't have a turbo head but it says something about stock appearance?

Charley

 

[Grimracer]

Charley and the rest of the gang. OB Nut this includes you my freind..

This question was brought to me by a few people. Some from my club members and some from out of state.

Also Charley im going to ask that for the time being we keep just this question on track. Thanks

TF.. for now i will hold off on my comments.. I will however let them be known as we get a chance to talk about this more.

Grim

 

[james irwin]

;D

we have tried it before ? couldnot seem to get it to work , as far as i concernend there is a better way

 

[Bill Zuber]

I agree with KRPNOVA tunnel hulls are a form of hydros and there is NO rule in IMPBA against turn fins on tunnels or any other type of Hydro.

 

[MikeP]

It seems to me that this wouldn't be brought up unless there appeared to be an advantage to using a turn fin.

The guy with the turn fin must be winning races ;D

Mike

 

[garrett randall]

If the boat in question is in D4, let me chime in as someone who attends almost all the races, but doesn't race the class. The boat that is in D4 does NOT win all the time. It has incredible speed, but does not corner well. There is another boat in D4/D6 (Bill Wachler) with a LeeCraft that just flies, and corners well. The boat in question has tried a turn fin, but there is nothing that I can find in the rule book that says that their can't be one. Someone before me mentioned the prather boats...they've had one for a long long time...

Garrett Randall

Good topic Mike!

 

[Ron Olson]

Seeing how there is no ruling on where or how it is placed, I would say yes, it is legal. MRP and Thunder Tiger both have tunnel hulls that have turns fins yet mounted at the CG, and the TT still has trim tabs. Gary's "trim tabs" are actually on there to "lengthen" the boat and move the CG forward without using weights on the front end.

Actually, I don't know of any class in IMPBA where you can't have a turn fin.

 

[Jack Garcia]

Not being an Impba member, I disqualify myself in the "turn fin" issue, but that does'nt mean I can't inject a little of my knowledge. Jim I and were discussing this and both of us agreed that we have gone through the trying to get a tunnel to turn scenario. The drawing says it all. Now if I can only get the drawing to post.

BTW, works dynomite.

 

[Slideblues]

Cool idea Jack I like it.

As far as anything else, I'll let the "powers that be"

deciede this one,

Gene ;D

 

[GTR]

Hi Guy's

I'm not in the US so don't have any rights but I still have an opinion. I believe tunnels should represent (even loosley) full size craft. That is part of the appeal of them. The turn fin on the inside of the tunnel I can live with as it doesn't detract from the 'look' - on the outside and you ain't fooling no one. I think it's funny that tunnels are classified as Hydros - you have rules for 1/8th scale and Sport series boats what makes tunnels different? If you are going to run a class like it represents a small version of fullsize I don't see how you can allow turn fins hanging off the outside to continue.

I am not a big fan of turn fins anyway because they cause massive damage when they hit someone elses boat. Without a fin maybe some prop cuts - with a fin tries to tear a chunk out of the poor guy on the receiving end.

Hay a fun problem to try and sort (legislate) out of.

GT ;D

 

[lohring-miller]

To repeat my post in another forum. Doesn't IMPBA have to certify a hull type? My very old rule book discusses that on page B-18. Since the XTR-21 hull should have been through this process years ago, does a boat with a turn fin still qualify? Otherwise, I see no mention of turn fins in either NAMBA or IMPBA rules.

Prather tunnels have run turn fins for years. They still won't win. By the way, all the other people I know who race the XTR-21 feel that they do not need a turn fin. From the comments I have heard, the turn fin must be an improvement. I'm well aware of Leecraft cornering "problems" and would like to run a turn fin on a boat to see the result myself.

Lohring Miller, owner B&M Leecraft

 

[Grimracer]

Tunnel Racers, Lohring

Most important is that we are not picking on anybodys setup, hull design or anything else for that matter.

Mike

 

[Joe Reese]

Can you see it !

R.C.M.B front cover:

.21 mod wins in the .67 class tunnel races.

 

[Brian_Loy]

I talked to Mike sometime ago about this. This is what I heard, and it is all all hear say, so correct me if I'm wrong. I was told that Tommy Lee`s record boats had been modifed to the point that they ran on the water like a hydro, and he used a turn fin for oval time . to do this I heard he cut out the center of the sponsons

I think there should be some kind of rule to keep a tunnel boat a TUNNEL boat.

Brian