Cornering on a tunnel.

Jeffmaturo · Nov 5, 2017

I read an old article from 2001 written by Jerry Dunlap. In it Jerry discussed the Leecraft XT460 tunnel hull and shared rigging and set up tips. I was surprised to see the addition of a strake on the left sponson. Is that something we should be running on current boats or just something that was needed on this particular design? I ask because to date, I have not seen a strake on a sponson before.

Thanks!

john v · Nov 5, 2017

I have that boat you are talking about, a b/m leecraft xt460. it was 15 years ago that I bought that hull but from what I remember that strake was a piece of wood glued on to the bottom and sealed. it wasn't part of the mold. my 21 hopper and the other ob tunnels I have seen I don't remember strakes . like you said maybe just for that design hull

Carl Van Houten · Nov 5, 2017

Jeffmaturo said:
I read an old article from 2001 written by Jerry Dunlap. In it Jerry discussed the Leecraft XT460 tunnel hull and shared rigging and set up tips. I was surprised to see the addition of a strake on the left sponson. Is that something we should be running on current boats or just something that was needed on this particular design? I ask because to date, I have not seen a strake on a sponson before.

Thanks!

Hello Jeff,

If you take every tunnel boat design that is out there, you can put 99% of them into two categories 1) Boats that are fast but don't turn well 2) Boats that turn well but are not fast. It is rare when you find a design that does both as expected. If I were you I would look at designs that are capable of doing both and make your decision based around what those boats have or don't have.

-Carl

RonShaw · Nov 5, 2017

Jeff,

When flying a tunnel properly, not much of the sponsons are in the water anyway, except in the turn. These strakes may make the tunnel ride funny as it may try to plane on the strakes. Strakes seem to work best on mono hulls. The art to turning tunnels is in the deadrise angles, rocker, deadrise twist on sponsons, auxillary stumble pad (width, depth, placement), and also very sharp edges.

LohringMiller · Nov 6, 2017

We built the Leecraft XT-460 both with and without the strakes. The best tunnel racers in the northwest swore by them, but it didn't seem to make much difference to me at my skill level.

Lohring Miller

Jeffmaturo · Nov 6, 2017

LohringMiller said:
We built the Leecraft XT-460 both with and without the strakes. The best tunnel racers in the northwest swore by them, but it didn't seem to make much difference to me at my skill level.

Lohring Miller

So basically training wheels for new boaters?

Jeffmaturo · Nov 6, 2017

Carl Van Houten said:
Jeffmaturo said:

I read an old article from 2001 written by Jerry Dunlap. In it Jerry discussed the Leecraft XT460 tunnel hull and shared rigging and set up tips. I was surprised to see the addition of a strake on the left sponson. Is that something we should be running on current boats or just something that was needed on this particular design? I ask because to date, I have not seen a strake on a sponson before.

Thanks!

Click to expand...

Hello Jeff,

If you take every tunnel boat design that is out there, you can put 99% of them into two categories 1) Boats that are fast but don't turn well 2) Boats that turn well but are not fast. It is rare when you find a design that does both as expected. If I were you I would look at designs that are capable of doing both and make your decision based around what those boats have or don't have.

-Carl

Hi Carl,

As a builder of winning boats, what is more important to you?

Jeffmaturo · Nov 6, 2017

RonShaw said:
Jeff,

When flying a tunnel properly, not much of the sponsons are in the water anyway, except in the turn. These strakes may make the tunnel ride funny as it may try to plane on the strakes. Strakes seem to work best on mono hulls. The art to turning tunnels is in the deadrise angles, rocker, deadrise twist on sponsons, auxillary stumble pad (width, depth, placement), and also very sharp edges.

Good input, thanks Ron.

Darin Jordan · Nov 6, 2017

Jeffmaturo said:
Hi Carl,

As a builder of winning boats, what is more important to you?

As someone who has had a little bit of success in FE OPC Tunnels, I'll take a couple MPH disadvantage in the straights to be able to corner at WOT any day of the week. If you do the math, you would too...

I love it when people tell me how "fast" their tunnels are. My follow-up question is always "cool, but how does it turn?". If they don't say they can turn at WOT, even in race water, then they are no longer a concern on the race course.

Carl Van Houten · Nov 6, 2017

Jeffmaturo said:
Carl Van Houten said:

Jeffmaturo said:

I read an old article from 2001 written by Jerry Dunlap. In it Jerry discussed the Leecraft XT460 tunnel hull and shared rigging and set up tips. I was surprised to see the addition of a strake on the left sponson. Is that something we should be running on current boats or just something that was needed on this particular design? I ask because to date, I have not seen a strake on a sponson before.

Thanks!

Click to expand...

Hello Jeff,

If you take every tunnel boat design that is out there, you can put 99% of them into two categories 1) Boats that are fast but don't turn well 2) Boats that turn well but are not fast. It is rare when you find a design that does both as expected. If I were you I would look at designs that are capable of doing both and make your decision based around what those boats have or don't have.

-Carl

Click to expand...

Hi Carl,

As a builder of winning boats, what is more important to you?

I don't use them.

-Carl

Christian Lucas · Nov 6, 2017

Hi ,

the big brother tunnels use powertrim and high of the motormount to corner and get a high straight speed. Its like a F 16 figther plane . A tunnel at top speed is realy flying and if you ad some stearing angle the boat will only look in that direction but is runing straight . To corner the big one lower the angle of attace , throttle the engine to let the front of the sponson get in contact with the water to get grip.

Coming out of the corner they rise the motorangle to rise the bow high reducing the wetted aera for best acceleration and then carfully trim down to find the right flyangle.Some combine it with a parallel motor high position. Sitting inside the tunnelhull helps with the popo meter to feel how the hull is flying. I have done some laps in Munich Gand Prix with Renato Molinari in his twin sitter tunnel , the son of the tunnelfather Angelo Molinari familie. http://svera.se/blogg/smorgardsbord/renato-molinari-racing-boat-history-and-information/ .

Form this reason i like to run a high trimed tunnel with turnfin to get grip at this position. Ed Fischer and his friend run the 045 Prather tunnel with outrigged turnfin succesfull ,that was the day i coppyed the turnfin and i loved it.

Happy Amps Christian

Grimracer · Nov 7, 2017

Reading in.......

Grim

LohringMiller · Nov 7, 2017

Jeffmaturo said:
LohringMiller said:

We built the Leecraft XT-460 both with and without the strakes. The best tunnel racers in the northwest swore by them, but it didn't seem to make much difference to me at my skill level.

Lohring Miller

Click to expand...

So basically training wheels for new boaters?

No, the really good drivers thought they were faster, but I had other driving issues that clouded any comparison.

Lohring Miller

Tommy Lee · Nov 7, 2017

Interesting discussion here-the XT-460 was not designed with sponson strakes nor did it need them. Strakes on the sponsons actually causes lift and will make the boat run cleaner in the straights but hurts in the turns because the strakes are trying to lift the boat and the rear of the boat needs to settle in the water for good turning. Some people are always trying things to make a boat "better" and this is okay but most changes do not improve the overall performance of a boat. I need to say-the XT-460 was introduced in 1984 and has won more races than all the other models (copies) combined and is still a competitive boat. There is no perfect boat. Every boat has it's problem areas.

Grimracer · Nov 7, 2017

and now.. listening in.........

Thank you Tommy

Grim

Carl Van Houten · Nov 7, 2017

Tommy Lee said:
Interesting discussion here-the XT-460 was not designed with sponson strakes nor did it need them. Strakes on the sponsons actually causes lift and will make the boat run cleaner in the straights but hurts in the turns because the strakes are trying to lift the boat and the rear of the boat needs to settle in the water for good turning. Some people are always trying things to make a boat "better" and this is okay but most changes do not improve the overall performance of a boat. I need to say-the XT-460 was introduced in 1984 and has won more races than all the other models (copies) combined and is still a competitive boat. There is no perfect boat. Every boat has it's problem areas.

Very True Tommy. There is no perfect boat. The turns are where the tunnel boats gets its true test. I have a question for you Tommy, Where does the "460" come from? I am sure it has some meaning. Does it have anything to do with the old Evinrude 4-60 racing engine or something else?

LohringMiller · Nov 8, 2017

One of my favorite tunnels with several interesting innovations is pictured below.

Lohring Miller

HTV Boats · Nov 8, 2017

I'm going to guess here as I don't know but 460 seems very close to the "D" class engine limit of .458 cu in. Maybe XT458 didn't sound right.

That said there are many ways to skin this cat and some ideas just work better. Back in the full size OPC days you added strakes, lift rails, and pads and drove the boat for feedback. I have found with models it's harder to figure out what is going on with changes just watching the boat. Some obviously have a keener eye and also test beyond the "butt dyno". Look at what hulls consistently place and the best cornering (handling) are there. Just carving a turn is part of the equation . How fast a speed you can enter and how fast you exit complete the deal. The width of the running surface, deadrise angle, and any progression of angles moving forward on the sponsons, plus tunnel depth make the boat. Different combinations work and some just better as I stated in the first sentence. Find the hull that works for you and your driving style.

Mic

Tommy Lee · Nov 8, 2017

Carl-the name came along after the introduction of the K&B 67 O.B.. Rod Geraghty and me were already talking about a boat and we wanted it to be a 40/60 boat and the name XT-460 was born. The boat performed great with a 67 engine with stock exhaust but that is about all the power it would handle. I have to disagree with you on the turning importance of a tunnel. Of course they need to turn well in racing but there is a lot more involved than just turning. I always set up my boats to run very loose (but under control) which meant better acceleration at the start and out of the turns. This is where most races are won. I also tried to make good starts and lived in lane-1-and nobody ever passed me in the turns on the outside. I still say if you cannot drive a free running tunnel with the throttle then you are not a good tunnel driver. If you have the boat set up tight enough to run wide open all the time then you are giving up performance. This might be different with today's engines but from what I have seen everything is still the same. When we were running K&b"s everything was a compromise. You gave up something in some areas to gain something in other areas.

Rokieboater · Nov 8, 2017

Throttle management--- What a unique concept.

Cornering on a tunnel.

Help Support Intlwaters:

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Similar threads

Join the conversation!

Join today and get all the highlights of this community direct to your inbox. It's FREE!