GF 16 Progress

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Cracker Larry
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Post by Cracker Larry »

Hello Tim. We've really been enjoying it! My wife and I have about got the freezer full of shrimp already. I decided on a 25 Merc. for power and I am very pleased with the performance.

http://gallery.bateau2.comdisplayimage.php?pos=-5327

Easy Poxy is great paint. I got it from a Boat US store in Savannah. It took almost a gallon for 2 coats inside and out. I rolled it on and tipped behind it with a foam brush. It is very shiny and hard as it is designed to be a finish coat. The Krylon/ Rustoleum is holding up fine. No it is not normal flat, it is specifically made for and called camoflage paint. Buy both brands because the colors are different even though the cap colors are the same. I only camo painted the bottom in the bow section where it is visable.

Every place we stop with the boat, someone tries to buy it from me! Very satisfying to get so many compliments on a homebuilt boat.

http://gallery.bateau2.comdisplayimage.php?pos=-5331

Here are my home made rod holders..

http://gallery.bateau2.comdisplayimage.php?pos=-5332

timoub007
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Post by timoub007 »

Larry,

Great additions to the gallery. That rig really turned out great. Hoping mine can hold a stick to yours. I'm counting on the flat, camo finish to hide some spots that should be sanded or faired more.

I'm going with a 25 hp too, but mine will be a Johnson, 3 cylinder. It weighs about 150 pounds where your Merc weighs about 100 pounds. I don't think 50 pounds will matter much and I want the extra torque of three cylinders. Plus I got a great deal on it off Ebay and it is electric start & oil injected.

Do you have a hand held GPS to get a speed on your rig? I'm curious what to expect from this light hull. Also, what is the draft as rigged?

Mine's coming along, and I'm still thinking I'll get it complete in the next 4-5 weeks.

Tim

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Cracker Larry
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Post by Cracker Larry »

Tim,

The boat is sensitive to weight in the stern. The Merc weighs 112 pounds and the boat tends to ride with the bow high, even with another person on the center seat. I installed a Doel Fin which helped but even with the motor trimmed all the way down the bow is still too high at lower speeds. I'm thinking of adding trim tabs. Plan of putting your beer, fuel and battery as far forward as possible. Even when I tested it with a 15 hp it rode with the bow high.

Draft is negligable. Maybe 3-4 inches at the stern. Less than that when planing..

Yes to the GPS. The hull is light, even though it was overbuilt. It will run about 43 mph. with 2 people. It won't win races but fast enough for a flat bottom boat.

timoub007
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Post by timoub007 »

Are you serious, 43 MPH with a 25 hp???!!!??? That has got to be some kind of record, and I can't wait to get mine done if that is true. I duck hunt on public land and speed wins you the spot you want.

Where is your gas tank? I think I read that you didn't do an electrical system, so I figure you don't have a battery.

I'm putting my gas tank under the bow deck and my battery under the middle seat. I put my access to the middle seat on the port side and the battery will go as close to that side as possible.

Good to hear on the draft. I've got a trick to help me get even skinnier too. Jacques doesn't like it, but I'm putting a tunnel in mine.

My aluminum beater with a 3 cylinder 40 Yamaha will barely top 30 MPH with a hunting load. I'm stoked to hear that your boat is as fast as you said.

Take care,
Tim
Last edited by timoub007 on Fri Sep 09, 2005 10:04 pm, edited 1 time in total.

Rick
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Post by Rick »

timoub007 wrote:Good to hear on the draft. I've got a trick to help me get even skinnier too. Jacques doesn't like it, but I'm putting a tunnel in mine.
The tunnel will make it ride lower in the stern and hurt your planing performance. It will draw more water, and not go as fast. I assume Jacques already mentioned this. There are good reasons why the XF20 is so wide. Good luck to you -- the Fur Elise (a D15) has a tunnel, which I thought was a questionable choice, too.

timoub007
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Post by timoub007 »

Rick,

Yes, Jacques has mentioned that and several other reasons why he does not like this modification. This will be my boat and that is how I'm going to build it though. It will be basically the same dimensions of my current aluminum boat, yet lighter. Where I fish and hunt has a very soft mud bottom and tunnel hulls are the norm. There are other additions to replace the surface area lost to the tunnel, thus putting the draft at or near the normal design.

The speed loss due to a tunnel is a design issue specific to the tunnel used. My production flats boat has a very large tunnel in it and subsequently is 7 MPH +/- than the hull without the tunnel. 50-51 versus 58-60 is a fair trade off for me. I am putting a fairly small tunnel in my GF-16 because of experiences I've had and local builders I've talked to.

The Fur Elise had many modifications that were both good and bad (from my point of view). While many think that the GF-16 hull is too narrow for a tunnel, there are many 36" & 42" bottom boats running the marshes around here that have tunnels. None of these boats (that I have ridden in) have shown any signs of chine tripping or other ill handling.

Have you built, driven or even gone for a ride in a tunnel hull similar to my build? Do you speak from some sort of experience or are you mearly repeating what you have read? If you know of first hand issues with what I'm doing to my hull I would really appreciate hearing them.

Larry,

Still hoping that your numbers are written as true.

Take care,
Tim

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Cracker Larry
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Post by Cracker Larry »

Have you built, driven or even gone for a ride in a tunnel hull similar to my build? Do you speak from some sort of experience or are you mearly repeating what you have read? If you know of first hand issues with what I'm doing to my hull I would really appreciate hearing them.

Larry,

Still hoping that your numbers are written as true.
No advise from me on the tunnel. Never ran one, never rode one.

But the speed number is true by Garmin, light load, maybe 300 lb. of people, 36 lb. gas under center seat, 80 lb. shrimp and ice in the bow. The tide was ebbing about 2.5 kts. Ran uptide and down then averaged the 2 numbers. Running about 45 downtide and 40 uptide SOG. The hull is light and slick. Remember it's rated for a 15.

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Post by Rick »

timoub007 wrote:Yes, Jacques has mentioned that and several other reasons why he does not like this modification. This will be my boat and that is how I'm going to build it though.
Go for it.
timoub007 wrote: Have you built, driven or even gone for a ride in a tunnel hull similar to my build? Do you speak from some sort of experience or are you mearly repeating what you have read? If you know of first hand issues with what I'm doing to my hull I would really appreciate hearing them.
Tim,

I've never been in a boat with a tunnel. There aren't many places on the west coast where they would make sense. I have read a lot about boat design and building, and have been reading this forum since the old format (2002?). The tunnel topic comes up frequently. You are a new poster on the forum, and sound like this is your first boat build (excuse me if I am wrong about this). If you have a lot of experience with tunnel flats boats that contradicts what I've heard elsewhere -- build on.

Like a lot of folks here, I try to contribute in areas where I think I can help, or when someone sounds like they are enthusiastically going the wrong way. I try to only share things that I know are right (I don't have to build an FL12 with a 50hp outboard to know that it's going to go Horribly Wrong), or that I have personal experience with.

I'm not sure why you end up sounding irritated at what I wrote. If you replace a smooth hull with the same hull with a tunnel cut-out, it will be slower -- as you wrote -- and it will ride lower in the water with the reduced volume aft. You may accept the small (your numbers show about 15%) speed decrease, and design around the reduced bouyancy (moving weight forward, for example), but you can't change the physics.

Build your boat and let us know how it works. I'm always interested in new ideas and new projects. No matter what happens it's not going to be one of those hideous Clorox-bottle "express cruisers." Best of luck in your build.

timoub007
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Post by timoub007 »

Rick,

I am truely sorry for the way my post sounded. I reread it and realized how harshly it sounded. I must have had a bad day and should have cooled down.

Thank you for your well wishes on my build. All you noted about a tunnel hull versus a plain bottom is true. What I disagreed with was how it will run in the end. I do accept the speed loss as the running draft is what is needed. The running draft will be less due to getting the prop and lower unit jacked up higher, maybe 4 inches or so.

Again, I am sorry for the way my previous post came across. This is my first build, but I'm not that new to the forum. I've been reading for about 2 years (just not posting much) and have had my plans for a year and a half. I also have the help of another builder, though not a S&G builder.

Larry,
I am sorry that I messed with your thread. I am exstatic about your speed though. Even with a 15% loss from my tunnel I'm looking at 36-37 MPH. That is awesome in my book for a 25.

Thanks,
Tim

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Cracker Larry
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Post by Cracker Larry »

Tim, no problem on the thread. This is Jacques board, not mine :D

FWIW, I tend to agree with Rick about the tunnel. Just doesn't seem to be enough boat to support it ,and the draft is insignificant as it is designed. Even as overbuilt as mine is. But WTF, people argue with me all the time. It's your boat, build it how you want it, that's why we build our own. It might work great and either way we may all learn something. I'd like to see some photos of it. Best of luck :!:

Where do you get the 15% number? Seems low to me, but again, I know nothing about tunnel hulls.

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