GV13 Garvey 13 May 2017

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Evan_Gatehouse
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Re: GV13 Garvey 13 May 2017

Post by Evan_Gatehouse » Wed May 31, 2017 2:15 pm

Before you get trim tabs - consider relocating battery and fuel tank up further forward. Lots cheaper!

Also - what HP is the motor and does it have remote trim?

Porpoising is basically the boat trying to find an equilibrium trim condition and moving weight forward is the usual cure.


designer: FB11/GV series/ HMD18/
SK17,21/MT24

tcason
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Re: GV13 Garvey 13 May 2017

Post by tcason » Wed May 31, 2017 3:23 pm

battery is forward of steering
Gas is under front deck
very minimal weight behind driver
minimal bow rise to get on plane
engine does have power tilt if tilt up porpoising gets worse
Porpoising happens at about 20 MPH and 4400 RPM when solo
boat can reach max RPM with 200 male pounds on front deck

Love this boat like driving a MG on the water

Boat will be used solo by me to fish about 80% of time

My research leads to
trim tabs
raise engine a notch
4 blade prop

engine HP is classified due to being over recommendation

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Evan_Gatehouse
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Re: GV13 Garvey 13 May 2017

Post by Evan_Gatehouse » Wed May 31, 2017 6:30 pm

Since a 20 HP is below the max recommended 25 HP and I think I saw a "0" in one picture...maybe you've got a 30 HP motor! That's the issue - it's 215 lbs according to Yamaha (and that is without the trim cylinders). 25 HP models are about 100 lbs less. I'm not so worried about the HP of the motor but its affect on overall weight distribution. That is what is causing the porpoising. Just too much weight aft.

For others reading this thread - these are light boats and using a motor of the recommended size will save you money (of course I used a 15 on a GV10 but that's OK since I designed it :)

I do not think a different prop will affect this at all. Save your money.

Speed matters as well. As you go faster the amount of boat in the water gets smaller, and goes aft. So higher speeds = greater amount of porpoising.

Fill a cooler full of ice water and strap it down up forward. As you catch fish, put fish in cooler, displacing the water :). Or 100 lbs of lead ingots in the bow locker, and move your battery further forward as well. Get a small 4 lb anchor and throw it in there too.

Small trim tabs are fairly cheap from Defender.com (I was surprised at the low cost). But if you think about it, as you deflect them downward you RAISE the bow - which is not what you want to do. They may help by extending the hull planing surface, and then you'd have them in an almost horizontal position. This probably will help with porpoising but it is not a guaranteed cure. The weight forward will certainly cure it.
designer: FB11/GV series/ HMD18/
SK17,21/MT24

tcason
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Re: GV13 Garvey 13 May 2017

Post by tcason » Wed Jun 14, 2017 10:00 am

dressing up the boat

The name came from my buddy who I sent the first picture to of the build to and his comment was "I give that boat a 50/50 chance of floating".




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Re: GV13 Garvey 13 May 2017

Post by tcason » Wed Jun 14, 2017 10:04 am

trim tabs installed
Hope to test drive this weekend and will provide follow up report

Bennett SLT trim tabs

link
https://bennetttrimtabs.com/self-leveling-tabs-slt/


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jwassdo
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Re: GV13 Garvey 13 May 2017

Post by jwassdo » Sat Jun 17, 2017 4:46 am

Beautiful boat. I had porpoising issues with my rb12, and one of the other guys suggested a hydrofoil. I'm sorry I didn't see your post sooner, this would have been much cheaper and easier and it did the job for me. I didn't use this particular brand but I think you get the idea.

Jeff

http://m.basspro.com/StingRay-Speed-XP- ... extensions

tcason
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Re: GV13 Garvey 13 May 2017

Post by tcason » Mon Jun 19, 2017 10:47 am

TRIM TABS installation is awesome

installed Bennett SLT6 tabs and took boat out this weekend and all porposing is gone!!

I can even trim the motor up to gain some RPM at full speed with no porposing

for future readers the GV13 design is great - I over powered with heavy motor and thus the need for trim tabs

Thanks for suggestion of hydrofoil on motor BUT I did not want this "look" on my boat

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Re: GV13 Garvey 13 May 2017

Post by Fuzz » Tue Jun 20, 2017 3:06 am

So how do you think a much lighter 30hp 2-stroke would do on her?
Said it before but that is one fine looking boat right there :D

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Re: GV13 Garvey 13 May 2017

Post by tcason » Tue Jun 20, 2017 10:04 am

My motor weight is 216 pounds.

Any lighter motor and closer to design weight (+ - 125 pounds) would be great and 30 HP is plenty to push her.
The great news is that a heavy motor can be corrected by the trim tabs for $125.

I love this boat and get compliments everywhere I go.
Last edited by tcason on Thu Jul 06, 2017 9:23 am, edited 1 time in total.

pee wee
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Re: GV13 Garvey 13 May 2017

Post by pee wee » Tue Jun 20, 2017 1:14 pm

Ah, 267 pounds . . . you've got quite a few ponies back there, maybe 60?!!

The boat looks great, but no wonder you needed a bit of help trimming things out.
Hank

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