BLUE GF18 by Jason

To help other builders, please list the boat you are building in the Thread Subject -- and to conserve space, please limit your posting to one thread per boat.

Please feel free to use the gallery to display multiple images of your progress.
User avatar
chiel
Frequent Poster
Frequent Poster
Posts: 92
Joined: Wed Apr 16, 2003 1:00 am
Location: Wateringen, The Netherlands

Post by chiel »

Holy "peep" that's definitely NOT what i wanted to hear. I do have a 7 gallon fuel tank under the castingdeck and i haven't fitted my console. i was planning of putting it at the same place as yours but i'm going to have a look at it again.

I'm going to run it with a 2-stroke motor so the weight will be less and the engine is also equipped with big fins on the cavitationplate to increase planing(decrease planing speed).

If i were you jason i'd first try the fins on your outboard. They are relatively cheap and could even be made by yourself.

Good luck!!!

Doug
Very Active Poster
Very Active Poster
Posts: 703
Joined: Tue Aug 27, 2002 1:00 am
Location: Houston Tx
Contact:

Post by Doug »

Based on your comments I assume you do not have electrically adjustable trim on the engine. You need to try moving the motor down/in with the manual trim adjustments before you start doing anything drastic. If it has some rocker like you indicated in another post you may have to add trim tabs or wedges (built in hook) but play with the weight distribution and your trim adjustments first.

jasonmcintosh
Very Active Poster
Very Active Poster
Posts: 1027
Joined: Fri May 23, 2003 1:00 am
Location: Sugar Hill, GA

Post by jasonmcintosh »

Doug wrote:If it has some rocker like you indicated in another post you may have to add trim tabs or wedges (built in hook) but play with the weight distribution and your trim adjustments first.
It doesn't sit on the bunks flat, but easily rocks on them. I'm quite sure that this is apart of the design. Perhaps Jacques put too much of a "reverse hook" into the design. I don't know. I adjusted the motor as far "forward" (or back depending on your perspective) as it'll go and shifted some weight forward. I'll be going out tomorrow to give it a try and will report how it went.

Thanks for everyone's thoughts.

Jason

User avatar
Grant
Frequent Poster
Frequent Poster
Posts: 168
Joined: Thu May 08, 2003 1:00 am
Location: College Station, Texas

Post by Grant »

Jason,

Really beautiful boat! The blue turned out very nice. Good luck solving your planing dilema.
Grant
FL14

jasonmcintosh
Very Active Poster
Very Active Poster
Posts: 1027
Joined: Fri May 23, 2003 1:00 am
Location: Sugar Hill, GA

Post by jasonmcintosh »

chiel wrote:Holy "peep" that's definitely NOT what i wanted to hear. I do have a 7 gallon fuel tank under the castingdeck and i haven't fitted my console. i was planning of putting it at the same place as yours but i'm going to have a look at it again.
I'm not panicing yet. I’ve only got one outing on the boat and a number of options for improving the situation. At this point I’m still determined to keep the console where it is. The fin is a good idea. I’ll keep it in mind.

Jason

golfconnection
Frequent Poster
Frequent Poster
Posts: 34
Joined: Wed Dec 31, 1969 7:00 pm
Location: Fort Worth

Post by golfconnection »

Not to derail this thread, but I see grant is from college station. If you could shoot me an email to johnlee@golfconnectionusa.com

Thanks

John Lee West

jacquesmm
Site Admin
Site Admin
Posts: 28215
Joined: Wed Aug 14, 2002 1:00 am
Location: Florida USA
Contact:

Post by jacquesmm »

BTW, there is no rocker (reverse hook) worth mentioning in that design .
The last 6' are absolutely straight. A little bit of rocker appear at 8' and becomes around 1/2" at 10'.
Take a straight edge to the plans, it is clear.
This maybe another possible explanation for the planing problem: you may have too much rocker.
The fact that the boat rocks on the bunks is an indication.
Let's check something: with the boat flat on the trailer, transom touching the bunks, what is the gap between the bunks and the bottom at 6' then at 8'.
If it is more than 1/4", it probbaly plays a role in the problem. In that case, fixed trim tabs, wedges or a Doelfin will help.
Jacques Mertens - Designer
http://boatbuildercentral.com

jasonmcintosh
Very Active Poster
Very Active Poster
Posts: 1027
Joined: Fri May 23, 2003 1:00 am
Location: Sugar Hill, GA

Post by jasonmcintosh »

I took yesterday off and went fishing with my son in the everglades canals. We had a great time catching lots of pan fish and some small bass. I love the boat layout, even though it’s killing its performance.

Before I bought it out, I trimmed the motor as far back as it’ll go, moved the starting battery (35 lbs?)from the back to the front, and put three 50 lbs bags of sand on the very front of the casting deck. Since my wife wasn’t with me, the sand pretty much replaced her weight from the first trip.

With my son (50 lbs) on the casting deck, I was able to get the boat up on plane w/o bouncing at somewhere between 1/2 and3 /4 throttle, but it would bounce if I went faster. Maybe I was going 20 MPH, but I’m just guessing. If my son got off the deck, I’d have to back off a bit.

Another annoying problem is that the boat goes a bit sideways, bow to port, stern to starboard. I’m going to try to compensate for this using the trim tab (anode thing) on the motor, but it may be due to me sitting well off center.

As far as handling goes, the boat is pretty solid. I didn’t get the foam sealed to the sole, so there is a little vibration in the sole that would have been nice to have eliminated, but other than that it’s an excellent boat. When taking corners, the boat does tend to slip sideways. The 1”x1” runners probably help, but right now I’m thinking that it would have been nice to have them 1.5” high rather than 1”. But of course this is supposed to be a shallow water boat, so that’s defeating the design a bit.

When I pushed the motor up to 3/4 throttle (past? not sure), the warning buzzer would sound. I assume this is the engine saying the RPMs are too high. The prop I put on the motor is just a used one from another 40 HP motor. I don’t know its pitch. I’m assuming that I’ll need to buy one with a greater pitch, but I could use some suggestions here. I mostly bought the 40 HP motor to ensure that the boat planes with a full load, not to go super fast. Is there a guide for the size and pitch of prop you need? How do you measure the pitch of a prop? The prop has so many curves, it’s hard to see one single angle.


Next steps:

It seems that I’m going to have to move the trolling motor up front. Don’t want to do it since I’ll have to blunt the nose on the boat (more work), and I’ll have bought 40 feet of 6 Ga wire for nothing. But every pound of weight I can move from back to front is worth two pounds of added weight in the front.

I like the idea of putting fins on the motor. Are they mounted to the cavation plate? Does anyone have experience with them?

Since tipping the motor back helped, I’m thinking “more is better”, so the idea of putting shims between the transom and motor mount is becoming more attractive to me. But there must be a limit to how much you can tip the motor w/o suffering other problem. Comments? Worth a try? I’ll do some measurement and maybe take pictures of where the cavation plate is relative to the hull and post them when I get a chance.

Jacques:

I believe that the back 6’ of the boat is flat, but the 17.5’ boat doesn’t sit on the last 6’ when it’s on the trailer. It sits more in the middle, which is why it rocks. I’m expecting that my three 2x4 bunks will eventually sag and reduce this, but for now it’s rocking.

All:

Again, and again, thanks for everyone’s help. Your comments are greatly appreciated.

Jason

User avatar
Davef
Active Poster
Active Poster
Posts: 402
Joined: Mon Nov 04, 2002 1:00 am
Contact:

Post by Davef »

Whe you say trimmed the motor back as far as it goes do you mean tilited the prop out or in? Also, did you raise the motor on the transom? The AV plate should be no lower than the bottom of the boat. Sometime you can get away with it being higher.

That buzzing is probably the motor overheating. With the motor trimmed way up (prop out as far as it goes) it may not be getting enough water. You should have a tach to figure out your rpm's. I don't think a buzzer would go off when you go over the recommended rpm. On newer motors it has a rev limiter on it but not older motors. If it is the temp, do not run it overheating. You will ruin the motor quickly. Sorry.

Keep us posted & we'll get it figured out for you.

jasonmcintosh
Very Active Poster
Very Active Poster
Posts: 1027
Joined: Fri May 23, 2003 1:00 am
Location: Sugar Hill, GA

Post by jasonmcintosh »

Dave,

I'm bringing the prop in, toward the transom. Previoulsy the prop was back, which put a slight downward force on the transom. Pulling the prop in should level this out, or perhaps push the transom up a bit.

I haven't EXACTLY measured the plate's position relative to the bottom of the hull. I'm thinking that it's a bit lower than the hull, but now that I moved the prop in, it's looking pretty close to being level with the hull. Perhaps it's a half in lower?? Not sure.

It'd be easy to move the motor up one set of mounting holes. That's probalby an inch or more, so I think that the plate would end up being above the hull. This is worth trying?

It's a 2003, 4 stroke motor. The buzzing seems to occur at a certain throttle position. If I give it more gass, it buzzes. If I back off, the buzzing immediately stops. If it was from heating I'd expect it to take awhile to cool down, so the buzzer wouldn't go off so quickly. I've only reved it up like this 2 or 3 times though.

>Keep us posted & we'll get it figured out for you.

Thanks. Sounds like a deal...

Jason

Post Reply

Who is online

Users browsing this forum: No registered users and 17 guests