My new Dillon Laker SC12 Tunnel!

**delawarerick** · 12-01-2024, 06:16 AM

Could you show some more pictures how you mounted that where you connected the ends I have been trying to use an actuator I have on a 1978 55hp johnson. Thanks Rick

**Spaceman Spiff** · 12-02-2024, 06:19 PM

Originally Posted by delawarerick;[URL="tel:3437744"

3437744[/URL]]Could you show some more pictures how you mounted that where you connected the ends I have been trying to use an actuator I have on a 1978 55hp johnson. Thanks Rick

here are a couple. The top one is just a stainless exhaust clamp and some aluminum angle brackets.

**Instigator** · 12-03-2024, 06:50 AM

Genius, love it!

Originally Posted by Spaceman Spiff

here are a couple. The top one is just a stainless exhaust clamp and some aluminum angle brackets.

**Spaceman Spiff** · 12-03-2024, 10:44 AM

Originally Posted by Instigator

Genius, love it!

Thanks. I got the idea from some of the people on the forum at dillon-racing.com

**Spaceman Spiff** · 05-17-2025, 03:15 PM

So I'm kinda stuck at 48mph. I get the onset of porpoising at that speed. Bob Dillon suggested I try to trim out to get past it, but I'm pretty sure I don't have enough trim left to do that. I tried a whale tail and sitting further forward about 8" and those had zero effect. I can't move any more weight around. What else can I try? Raising or lowering the motor, or adding cup to the prop? If I raise it with this prop, it will induce slip. I bought Jim's Tunnel Hull book, but I have no idea where it is.

**Jimboat** · 05-18-2025, 04:42 PM

Here's an article on Porpoising that may help.

**Spaceman Spiff** · 05-19-2025, 04:41 PM

Originally Posted by Jimboat

Here's an article on Porpoising that may help.

Thank you so much! Just what I needed. I also found my book, buried in the garage.

**Spaceman Spiff** · 05-19-2025, 08:07 PM

With my 1/8 of a ton body weight, I wonder if I should be moving the weight back toward the stern?

**Spaceman Spiff** · 06-02-2025, 10:53 AM

Originally Posted by Spaceman Spiff

With my 1/8 of a ton body weight, I wonder if I should be moving the weight back toward the stern?

I put a couple of sand bags (maybe 60lbs total) right at the transom and that changed the angle of attack dramatically. Tied up to the dock, the rear of the deck was even with the surface of the water. I was able to get up to at least 46 without even trimming it out at all. 39 was about all I could do before at full negative trim. It was really choppy out there with a 15mph wind so I couldn't get too squirrely with it because I was close to stuffing a couple times. But, it seemed to like the shift in weight to the back. Can't wait to get back out there early in the morning when the water is usually glass.

**Spaceman Spiff** · 06-07-2025, 12:36 PM

Well, I got cleaner water today and got about same the results. I even raised my engine up 1/2". It still hits the hump zone about 46mph. The hydrodynamic stability starts to fade at that speed. The rear seems a little "loose". I set my tachometer to 12 poles and that seemed to make it tell the truth. I'm running about 5200rpm at 46mph with the 21P prop. I still can't get myself to trim it out beyond 48mph. I think I need to find a short shaft motor before I can really start to trust the rear.

Would adding cup to the prop help it hold up the bow better, possibly moving the hump zone to a higher speed?

**CUDA** · 06-08-2025, 09:30 AM

You have a lot of weight forward, be interesting if you could move back in the boat a foot or two, find a 120lb person in there and see how boat reacts .

**dagodiver** · 06-10-2025, 06:50 AM

my underpowered 16' Seebold tunnel handles a lot better and runs a lot better now with the CG forward.
I rested it on a 8x8 to figure where the cg was. Im at 35% from the trailing edge of sponson.
Only runs in the mid 70's so certainly not "flying" but will do better when I put some better power on it
after the "car" is ready for the car shows again.
Your boat is super cool.!! i will build one soon.
I have all the plans.

Dago.

**Spaceman Spiff** · 06-10-2025, 07:11 PM

Originally Posted by dagodiver

my underpowered 16' Seebold tunnel handles a lot better and runs a lot better now with the CG forward.
I rested it on a 8x8 to figure where the cg was. Im at 35% from the trailing edge of sponson.
Only runs in the mid 70's so certainly not "flying" but will do better when I put some better power on it
after the "car" is ready for the car shows again.
Your boat is super cool.!! i will build one soon.
I have all the plans.

Dago.

Thanks, and good luck with your build.

It's interesting though, I've tried moving the weight forward and back now and the hump zone still starts at 46mph.

**CUDA** · 06-10-2025, 07:54 PM

At 260 lbs he has plenty of weight forward

**dagodiver** · 06-11-2025, 09:22 AM

Originally Posted by Spaceman Spiff

Thanks, and good luck with your build.

It's interesting though, I've tried moving the weight forward and back now and the hump zone still starts at 46mph.

Have you found the CG of the hull with you in it.?
Then the fuel should go on top of that point when you find what works.
So as you burn fuel the CG stays the same you just get lighter.

Dago