Need rigger advice

[T.S.Davis]

(5245MG I think) on my full size JAE and it turns great.

Mine too. Takes almost no rudder throw to turn these.

If you give a rigger too much left to course correct it can climb the fin and lift that sponson up out of the water. Not always but it does happen.

[Chilli]

Joe, Run the straigt edge from the bottom of the sponson to bottom of the ski to show you where the water surface would be. You can also eye ball it looking from the back of the boat. You will quickly realize how the bottom of the turn fin can cause the sponson to dig in the water in the position you have. Putting fin mounting screws being in the middle of the slots is usually pretty close since the mounting holes on the sponson for the fin are bored parallel with the running surface. As Terry mentioned, Any hard left turn will lift the right sponson. A poorly sharpened or tapered fin can also cause lift. Don't change more than one thing at a time if you can help it. The turn fin angle is the biggest problem right now and I bet you will see a noticable difference in performance adjusting that first.

Your KV should be okay for 3S but only a very short 4S run. But I don't run the leopard motors so I cant say for sure.

[spectre]

Joe, Run the straigt edge from the bottom of the sponson to bottom of the ski to show you where the water surface would be. You can also eye ball it looking from the back of the boat. You will quickly realize how the bottom of the turn fin can cause the sponson to dig in the water in the position you have. Putting fin mounting screws being in the middle of the slots is usually pretty close since the mounting holes on the sponson for the fin are bored parallel with the running surface. As Terry mentioned, Any hard left turn will lift the right sponson. A poorly sharpened or tapered fin can also cause lift. Don't change more than one thing at a time if you can help it. The turn fin angle is the biggest problem right now and I bet you will see a noticable difference in performance adjusting that first.

Your KV should be okay for 3S but only a very short 4S run. But I don't run the leopard motors so I cant say for sure.

Txs for the help. I took some pics of what I think your saying with level from sponson to ski on tub wetted area. Hope this helps. I also have a strut pic to.

[StevenBryant]

From what i can see the front right sponson is lifting when you are using left rudder, this will cause the boat to ride up on the turn fin as T.S Davis mentioned.

[spectre]

I put a new servo in today and waiting on batt so I can check CG. In it current CG, with old batterys the way I ran it it lines up with the last screw on the fin. So you would like cg to be more forward or is this 1/3.

Also you can see the fin is sharpened on the outside in two of the pics, don't know about the thinning tho and how far you recommend. txs again joe

[spectre]

Yes its doing that riding up as you say.But when I come out of a turn and accel it pulls right, you can see it in the vid when it accels.

From what i can see the front right sponson is lifting when you are using left rudder, this will cause the boat to ride up on the turn fin as T.S Davis mentioned.

[Doug Smock]

Yes its doing that riding up as you say.But when I come out of a turn and accel it pulls right, you can see it in the vid when it accels.

It seems like it's pulling right because you don't have enough rudder in the water. The prop is pulling the transom left. You need a longer rudder blade or you can move your rudder bracket closer to the bottom of the transom. The red boat in the pics could use a bit more rudder depth. Even with a Limited set up it requires a bit of left trim.
The information you're receiving on the fin is spot on. When you look across the top of the tub with the left sponson closest to you, the top of the fin should be on a parallel line with the tub.


Note: You can get by with just the left half of your strut bracket. Just back up the other side.

Use the 60/40 rule on the CG. 60% of the weight on the sponsons, 40% on the ski. That should put your CG approx. 13.25" from the transom.

[spectre]

It seems like it's pulling right because you don't have enough rudder in the water. The prop is pulling the transom left. You need a longer rudder blade or you can move your rudder bracket closer to the bottom of the transom. The information you're receiving on the fin is spot on. When you look across the top of the tub with the left sponson closest to you, the top of the fin should be on a parallel line with the tub.


Note: You can get by with just the left half of your strut bracket. Just back up the other side.

Thank you Doug, the last pic is very telling with the rudder mounted further down the transom. Not sure I can move bracket down yet. I measured the rudder and it is 92.15mm or 3.6inch long, Do they sell a longer one?]. Txs for the tub hint too. joe

PS Good eye, I just measured how much rudder is in water from back of tub ski, its only 1inch in the water or about 25mm, basic recommend about 50mm in water sound good?

[spectre]

O ship. I cant move servo. I would need low profile servo and low mounts to attempted that.

[Chilli]

Is your strut flat on the ski?? It's hard to tell in the pic. If so then the strut is running too negative which is pushing the front sponsons down. You want the strut as low as possible on the ski but place the boat on a flat surface without the turn fin. The strut should be parallel with the surface. Some run a touch of negative. To get my strut in the correct position, I cut the nose off and then flattened the bottom of the strut a bit where it contacts the ski. I forgot about the 60/40 rule for the JAE. Not too many people have built more JAE FE's than Doug.

[Namba328]

Joe, Run the straigt edge from the bottom of the sponson to bottom of the ski to show you where the water surface would be. You can also eye ball it looking from the back of the boat. You will quickly realize how the bottom of the turn fin can cause the sponson to dig in the water in the position you have. Putting fin mounting screws being in the middle of the slots is usually pretty close since the mounting holes on the sponson for the fin are bored parallel with the running surface. As Terry mentioned, Any hard left turn will lift the right sponson. A poorly sharpened or tapered fin can also cause lift. Don't change more than one thing at a time if you can help it. The turn fin angle is the biggest problem right now and I bet you will see a noticable difference in performance adjusting that first.

Your KV should be okay for 3S but only a very short 4S run. But I don't run the leopard motors so I cant say for sure.

Btw chili I run the same motor in my p-sport hydro and it runs like a bat out of hell

[spectre]

Chilli the strut is flat on top of the ski and is negative.. I would like to shout out to Namba328, Doug and chilli for giving me some good basics I needed and found a big issue. I did order a longer rudder from OSE to see if I can make fit. I plan on building on new rigger with what I learn from this boat. Thanks again for the help , I would have been totally lost with this info, nice to learn some things and improve on them. joe