Question for Jacques

[Aripeka Angler]

Question for Jacques or anyone with tunnel venting experience.
I’m ready to finally punch the vent hole in the tunnel of my XF20.
Should I drill the vent hole in the forward sloped plane of the tunnel or in the top on the forward side of the tunnel?
If the hole is to be on the slope, does it need to be near the bottom or top of the slope?
I’ll be using a 1-1/2” thru-hull. Is this a good size?
The hose from the tunnel will be routed through the bulkhead behind the helm. At the penetration will be a 1-1/2” thru-hull as well.
I’m thinking about putting a ball valve under the deck to fine tune the air flow.
I’ve been putting this off for years, ready to get it done...

[Dr. Pete]

New in the game. Building the Xf 20 presently. AA you have been suggested to make an acquaintance to have in my “am I worthy?” library. I have been trolling for a couple of years. My stage is the craft is capsized in the barn just now glassing all the seams. Opportune time to do this vent in the tunnel. What is this about? So far this has been as fun as anything I have ever done with my clothes on! Thanks and really happy to finally be building! Pete

[Aripeka Angler]

New in the game. Building the Xf 20 presently. AA you have been suggested to make an acquaintance to have in my “am I worthy?” library. I have been trolling for a couple of years. My stage is the craft is capsized in the barn just now glassing all the seams. Opportune time to do this vent in the tunnel. What is this about? So far this has been as fun as anything I have ever done with my clothes on! Thanks and really happy to finally be building! Pete

Hi Doc,
I’ll be delighted to help you with your build!
Ask away, pm or email or hit me up on my Bare Bones thread.
The tunnel vent is supposed to reduce drag and turbulence in the tunnel.
It is said to increase speed and fuel economy.

[Capt UB]

I guess it depends on the design of the hull, right?
I'm building the LM18 without the tunnel. JM thinks it not such a good idea to put in a tunnel, on this LM18. Also, venting was a bad idea. It's in the plans.

[Fuzz]

I know nothing when it comes to venting a tunnel but I think I have read where JM says not to do it.
That being said if you vent your hull and have a seacock on it you can always adjust or even shut it off as needed. All it will cost is a little bit of hardware and you will have your answer.

[jacquesmm]

Don't vent. the tunnel. It sends air to the prop.

[willg]

AA, this is a link to a thread where a guy vented the tunnel in his Kenner. He said running the tunnel vented or not was like having two different boats. He'd keep the vent open unless he was on the flats. Presumably he had a jack plate to lower the motor because, as Jacques said, the prop wouldn't get water when the tunnel is empty.

https://www.2coolfishing.com/ttmbforum/ ... p?t=371284