Gas Lobster Boat Losing Speed In The Turns

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Joined
Nov 18, 2005
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Im trying to figure out how to fix this. The boat is basically a 22 lb rigger. It turns ok but to stay in lane one it scrubbs Alot of speed. Ive thought about moving the rudder to the left side. Im also wondering about the turn fin. The cg is 2 to 3 inches behind the center of the turn fin. Would moving it back help?

Any thoughts?
 
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Im trying to figure out how to fix this. The boat is basically a 22 lb rigger. It turns ok but to stay in lane one it scrubbs Alot of speed. Ive thought about moving the rudder to the left side. Im also wondering about the turn fin. The cg is 2 to 3 inches behind the center of the turn fin. Would moving it back help?

Any thoughts?
Wes,

Keep in mind that is a BIG boat and may not be a happy camper pinned in lane one. When I ran my 1/8th lobster set up was very important including the CG. Mine cornered best with the CG right at the center of the turn fin.
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larger turn fin.... minimize the slide..

Also try rounding the leading edge to bottom edge of the rudder.. start with a quarter and you might have to go larger.

Grim
 
What about the Boat Whisper? That boat will never hold lane one without killing it on speed
 
I think you may have hit it. I have a deeper flat blade that I can try. It is wider than the tyndal blade and I can set it back, closer to the cg. None of that will hurt the straight away speeds. I'm afraid a deeper strut will hurt me down the straight . I love the way this boat drives. It is just like a rigger.....just a FAT rigger. lol
 
Wes how far behind the sponson transom is the centerline of your turn fin?
Im not sure which way your talking about. It is a tyndal fin and is nearly against the transom. I have it all the way to the right edge of the ride pad. I was looking at it this morning and I am going to have to come up with a brace or turn buckle like the real boats (from the side of the hull to the turn fin) if I am to move back any. There has got to be ALOT of pressure on that thing and the farther I move back, the more strain I will put on the transom.
 
Wes how far behind the sponson transom is the centerline of your turn fin?
Im not sure which way your talking about. It is a tyndal fin and is nearly against the transom. I have it all the way to the right edge of the ride pad. I was looking at it this morning and I am going to have to come up with a brace or turn buckle like the real boats (from the side of the hull to the turn fin) if I am to move back any. There has got to be ALOT of pressure on that thing and the farther I move back, the more strain I will put on the transom.
My CG is about 7.5" back from the transom and the center of the turn fin is about 3 to 3.5" back. That seems like a long way to me even for a 1/6 scale. I have the motor forward, as well as having my fuel cell and radio box all in the nose.
 
Wes how far behind the sponson transom is the centerline of your turn fin?
Im not sure which way your talking about. It is a tyndal fin and is nearly against the transom. I have it all the way to the right edge of the ride pad. I was looking at it this morning and I am going to have to come up with a brace or turn buckle like the real boats (from the side of the hull to the turn fin) if I am to move back any. There has got to be ALOT of pressure on that thing and the farther I move back, the more strain I will put on the transom.
My CG is about 7.5" back from the transom and the center of the turn fin is about 3 to 3.5" back. That seems like a long way to me even for a 1/6 scale. I have the motor forward, as well as having my fuel cell and radio box all in the nose.
Yeah you need to see if you can get that CG as close to the center of the fin as you can, having the pivot point (the fin) so far ahead of the CG is not helping you at all. A 3-4" move will most likely dictate getting the weight in the sponson tips to maximize the CG move vs. weight added. The way I've done it before is by drilling a small hole on the inside flat surface near the sponson tips and pouring #8 lead shot (.080" diameter) into the hole followed by West epoxy and plugging the hole when cured. I took regular lead weight strips and stacked them equally on each sponson tip until the boat was close then poured the same weight of lead shot into the sponsons with the boat standing on the sponson tips strapped to the work bench to keep it vertical. When I ran my 1/8 lobster and got the CG on the fin centerline it was a night and day difference and the boat was awesome through the turns, just ask anyone in D12 who had to chase it.
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Wes how far behind the sponson transom is the centerline of your turn fin?
Im not sure which way your talking about. It is a tyndal fin and is nearly against the transom. I have it all the way to the right edge of the ride pad. I was looking at it this morning and I am going to have to come up with a brace or turn buckle like the real boats (from the side of the hull to the turn fin) if I am to move back any. There has got to be ALOT of pressure on that thing and the farther I move back, the more strain I will put on the transom.
My CG is about 7.5" back from the transom and the center of the turn fin is about 3 to 3.5" back. That seems like a long way to me even for a 1/6 scale. I have the motor forward, as well as having my fuel cell and radio box all in the nose.
Yeah you need to see if you can get that CG as close to the center of the fin as you can, having the pivot point (the fin) so far ahead of the CG is not helping you at all. A 3-4" move will most likely dictate getting the weight in the sponson tips to maximize the CG move vs. weight added. The way I've done it before is by drilling a small hole on the inside flat surface near the sponson tips and pouring #8 lead shot (.080" diameter) into the hole followed by West epoxy and plugging the hole when cured. I took regular lead weight strips and stacked them equally on each sponson tip until the boat was close then poured the same weight of lead shot into the sponsons with the boat standing on the sponson tips strapped to the work bench to keep it vertical. When I ran my 1/8 lobster and got the CG on the fin centerline it was a night and day difference and the boat was awesome through the turns, just ask anyone in D12 who had to chase it.
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Oh, I seen u run before! I think I'm gonna start with moving the fin back some. Then I'll ad weights. The retrieve boat guys are already wanting me to install a tow hook lol. Do you think a flat fin with say a 10% angle will b ok? Or do I need to use the tyndal fin and send it back a few inches? The tyndal fin was actually coming out of the water some with the wake of the other boats. It would skip out a lane in the turns.
 
Wes I think your CG is WAY too far back like Don was saying. Normally on a hydro the CG is 1 to 2 inches behind the rear of the sponson transom. Don's information is spot on here. I'm not sure which fin you are using, but you may need that REALLY WIDE fin that I made for you a few years ago for this boat. Make sure you have about 2 1/4 to 2 1/2 inches of fin in the water, also. Don't move the fin before you get the CG back to about 1 to 1 1/2 inches behind the sponsom transom. One change at a time.........the boat will let you know if it likes it or not.

Dick Tyndall
 
Wes I think your CG is WAY too far back like Don was saying. Normally on a hydro the CG is 1 to 2 inches behind the rear of the sponson transom. Don's information is spot on here. I'm not sure which fin you are using, but you may need that REALLY WIDE fin that I made for you a few years ago for this boat. Make sure you have about 2 1/4 to 2 1/2 inches of fin in the water, also. Don't move the fin before you get the CG back to about 1 to 1 1/2 inches behind the sponsom transom. One change at a time.........the boat will let you know if it likes it or not.

Dick Tyndall
Hay there Mr. Turnfin! Ya that is and was the design flaw in that boat. They had the same problem with the real one as well. The sponsons should have been way farther back on the boat. Like I said, I have everything up in the nose. I even cut into the boom tube to get the motor forward.

Yes! i have that monster fin on it now but it needs to be a 1/2 inch deeper still and farther back closer to the CG. I am hesitant to add weight simply because it is heavy already. If I can get my boat whisper (Ken Hildreth) out to the lake this weekend I may just strap on a few pounds of lead to the sponson tips just to see what happens. I hate the idea of changing out your fin unless I have to.
 
The reason I use the #8 lead shot is because it's so small and you can get it all the way up in the tips of the sponsons without any dead space. Do the best you can to get that CG closer to the vertical centerline of the turn fin.
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The reason I use the #8 lead shot is because it's so small and you can get it all the way up in the tips of the sponsons without any dead space. Do the best you can to get that CG closer to the vertical centerline of the turn fin.
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On my way to the lead store now. We'll see what happens.
I buy my lead shot at the local gun shop, very popular size for shotgun shell loading.
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Listen to what Don say's his lobster boat was super fast and handle great. (very hard to beat)




Nails
 
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