Tunnel Mite Question

Outboard designs up to 14'

Moderator: ttownshaw

weasel
Posts: 46
Joined: Sat Dec 12, 2015 1:31 pm
Location: Clear Lake, MN
Contact:

Tunnel Mite Question

Postby weasel » Mon Jun 04, 2018 4:04 pm

I just built the Tunnel Mite and I put a 25hp Yamaha on it, and it looks great! I took it for a spin yesterday and I have a few questions for someone that has built or driven one before. I am wondering why it feels like it is going to dig into the water and grabs and goes one direction or another at times. It feels like it's walking or grabbing once in a while. Is this the way it rides, or does the motor have to be tilted way up, it's a little spooky so far? Maybe I just need to get use to the feeling. Thanks for any info anyone has. Weasel
Attachments
Sea Demon #1.JPG
Last edited by weasel on Tue Jun 05, 2018 5:50 pm, edited 1 time in total.

User avatar
Roberta
Posts: 6143
Joined: Tue Jul 31, 2007 5:23 pm
Location: East Troy, Wisconsin

Re: Tunnel Mite Question

Postby Roberta » Mon Jun 04, 2018 5:12 pm

The boat was designed to be powered by short shaft motors up to 100 lbs. Your 25 hp Yamaha may be too heavy and possibly a long shaft creating an unbalanced condition.

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

weasel
Posts: 46
Joined: Sat Dec 12, 2015 1:31 pm
Location: Clear Lake, MN
Contact:

Re: Tunnel Mite Question

Postby weasel » Tue Jun 05, 2018 9:31 am

Thanks for the reply, anything might help! I have a short shaft, and it's listed at 108 lbs. I see a lot of these boats on the videos with the same 25hp motor hmmm? They are also going wide open across waves, and seem to be riding nice. There is a video out there where a guy and his kid were both in it and it rode good hmmm. They had to be at least 250lbs combined weight. Maybe I was sitting a little too high up in my boat so I am going to try and sit just on a boat cushion then it won't be quite as top heavy and tippy. Thanks for any answers.

User avatar
hoodman
Posts: 1797
Joined: Thu Nov 10, 2011 8:48 am
Location: Lafayette, IN

Re: Tunnel Mite Question

Postby hoodman » Tue Jun 05, 2018 3:04 pm

Congrats on finishing your tunnel mite! We'd love to see pictures of it. Is it happening just at full throttle or any time you are up on plane? It may just take some getting used to driving it.

PeterG
Posts: 542
Joined: Mon Dec 03, 2007 7:08 am
Location: Connecticut

Re: Tunnel Mite Question

Postby PeterG » Tue Jun 05, 2018 6:47 pm

There is a chance the fore/aft balance is off, maybe a bit bow heavy? I don't know your equipment layout but try moving some weights like the fuel tank aft, battery too if you have one. At speed I've seen these riding on the aft third of the hull length but I have no experience driving one.
Murphy's Law: Anything that can go wrong, will go wrong.
Griffin's Law: Murphy was an optimist.

User avatar
Roberta
Posts: 6143
Joined: Tue Jul 31, 2007 5:23 pm
Location: East Troy, Wisconsin

Re: Tunnel Mite Question

Postby Roberta » Wed Jun 06, 2018 6:03 am

Looks very nice. I think maybe the seat might be placing a C/B point high and could be causing the boat to wallow from side to side. These boats were designed to be driven with the driver positioned low in the cockpit. More of a kneeling, hunched down position. Smaller people might get away with sitting up higher, but larger folks could create a balance issue being too high in the saddle.

Roberta
Roberta "Queen of the Boat Builders"
Built Zip "Oliver IV", Super Spartan "Jimmy 70", and Torpedo "The Glen L".

weasel
Posts: 46
Joined: Sat Dec 12, 2015 1:31 pm
Location: Clear Lake, MN
Contact:

Re: Tunnel Mite Question

Postby weasel » Wed Jun 06, 2018 7:38 am

Thanks Roberta, I believe you are correct. I thought the same but wasn't sure. So I took the adjustable seat brackets that I custom made under the seat out. That lowered it about 5 inches down. So I'm going to try that. Now it wont be adjustable but hopefully will ride better. It did sway a bit so I think the problem is a little too top heavy. Especially with me (200) in it the max weight. Thanks for your input, I will let you know the next time I take it for a spin.
Attachments
Tunnel Mite #6.JPG
Tunnel Mite #5.JPG

weasel
Posts: 46
Joined: Sat Dec 12, 2015 1:31 pm
Location: Clear Lake, MN
Contact:

Re: Tunnel Mite Question

Postby weasel » Mon Jun 25, 2018 6:24 pm

008.JPG


I did take it for another spin with the seat lowered about 5 inches. I am sitting at 5" off the floor now. It road a lot better, I can get it up to about 20 miles an hour and cruise around just fine now (better than before). When I get to about 23 mph or more it starts to dig and dart around and feels like it's going to catch and flip. It should float on air that goes underneath the tunnel, the faster you go. I am wondering if the motor needs to be lowered a bit and if that would make any difference. When I take off at the beginning it does push air just on top of the surface until it gets going a bit, then it is fine and in the water cruising. I tried tilting the motor at different angles and that doesn't make much difference. Would a bigger fin on the motor plate make a difference? I put a photo of the back section behind the seat (gas tank,oar,battery), hope it got on here. Any info/experience would be great. It's a blast to drive, but I would like to go a little faster and be safe HMMM.

lakeracer69
Posts: 192
Joined: Sun Dec 19, 2004 8:14 am
Location: NH

Re: Tunnel Mite Question

Postby lakeracer69 » Mon Jun 25, 2018 8:11 pm

Little Hydros are not designed to sit "on" them. Get rid of the seat and get a thin pad to kneel on. You move your body weight forward and aft and side to side to adjust handling on the fly.

That seat has got to go. It will also get you center of mass lower in the boat when it's removed. Try it, I'll bet it's like night and day for you.
As Conan the Barbarian says, " It's not how hard you can hit, it's how hard you can get hit and remain standing".

weasel
Posts: 46
Joined: Sat Dec 12, 2015 1:31 pm
Location: Clear Lake, MN
Contact:

Re: Tunnel Mite Question

Postby weasel » Tue Jun 26, 2018 6:24 am

Thanks racer for the reply.
I do have some tips on building it, but not riding it yet LOL. I am going to get just a little pad or make a 1" thick seat seat then. I have an "artificial leg" so I can't kneel in the boat, but a really low, light weight seat I think will make just enough difference. The back of the seat is helpful for getting in/up/down in the boat too, it would be nice to keep if possible. The lower one goes the more stable it becomes it's beginning to look like. Can't wait to try another test run soon here!! Thanks again.

lakeracer69
Posts: 192
Joined: Sun Dec 19, 2004 8:14 am
Location: NH

Re: Tunnel Mite Question

Postby lakeracer69 » Tue Jun 26, 2018 7:05 am

Sorry, I didn't realize that was an issue. When running these things I've found myself hanging all over them.
Especially when getting up on plane I am usually waaaay forward until the bow settles down on plane. Lower center of mass is definitely better. You can also google "rev sticks" to fine tune your motor height if required. Basically like thin paint stirring stick(s) stuck under the clamping bracket. Racers use these to fine tune the height of the cavitation plate in relation to the boat bottom.
As Conan the Barbarian says, " It's not how hard you can hit, it's how hard you can get hit and remain standing".

weasel
Posts: 46
Joined: Sat Dec 12, 2015 1:31 pm
Location: Clear Lake, MN
Contact:

Re: Tunnel Mite Question

Postby weasel » Tue Jun 26, 2018 9:26 am

All I have available now to move is the tilt, unless I filled and drilled new holes (eeeesh). It is clamped with the normal hand screws on top and has the mounting bolts through the mounting bracket at the bottom through the transom. I don't think I could move it any higher it already blows some air at take off until it gets on plane then it's in the water. Do they do a little better with stability farther into the water than that? I have the trim tab straight on the motor, I don't know if that needs to be turned slightly against the motor force, so at higher speeds it doesn't pull? Could that be an issue? I'm not worried about going super fast, I just want it to be stable at higher speeds. Thanks again, your info is helpful.


Return to “Small outboards”

Who is online

Users browsing this forum: No registered users and 7 guests