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With the exception of the JAE, most of us setup so that the rear sponsons do not touch the water at speed. The same for the front sponsons. Instead, it rides on a cushion of air. With the JAE, it is a planing surface and does touch the water. To answer the question, anything touching the water can create drag. At higher speeds, above 70mph, aero-drag is also a concern.
For your application and if you decide to work from the JAE plans, I would talk to those who build and run them successfully. The specific questions I would ask would be related to their total weight RTR. When you scale up to accommodate 8s batteries, pay special attention to the width of the sponsons. While they are fairly neutral while in flight, they do generate lift to offset the weight of the components. You may need to add an additional 1/8" and maybe even 1/4" to the sponson width to keep her from running too wet. However...
Build it to the larger scale and try it. Then make adjustments as necessary such as swapping the sponsons after the fact. You may find that a simple change in COG (Center of Gravity) may have the desired results you are looking for. You may also find that you like to run the model on 6s after built. That rear ski on the JAE may in fact be very advantageous for running in rough conditions. I say try it! You never know unless you do. Then share your results and many of us can suggest some ways to get her running faster, more stable, or adjust to different water.
To see a rigger setup for oval doing 80mph, checkout Steve Reesor's rigger here: http://www.youtube.com/watch?v=tnYXfOo637A He's running 10s2p, but it gives you a good idea of what you're in for if you've never operated a model at these speeds. Stability is the key. Without stability, you end up with a lot of pieces.
For your application and if you decide to work from the JAE plans, I would talk to those who build and run them successfully. The specific questions I would ask would be related to their total weight RTR. When you scale up to accommodate 8s batteries, pay special attention to the width of the sponsons. While they are fairly neutral while in flight, they do generate lift to offset the weight of the components. You may need to add an additional 1/8" and maybe even 1/4" to the sponson width to keep her from running too wet. However...
Build it to the larger scale and try it. Then make adjustments as necessary such as swapping the sponsons after the fact. You may find that a simple change in COG (Center of Gravity) may have the desired results you are looking for. You may also find that you like to run the model on 6s after built. That rear ski on the JAE may in fact be very advantageous for running in rough conditions. I say try it! You never know unless you do. Then share your results and many of us can suggest some ways to get her running faster, more stable, or adjust to different water.
To see a rigger setup for oval doing 80mph, checkout Steve Reesor's rigger here: http://www.youtube.com/watch?v=tnYXfOo637A He's running 10s2p, but it gives you a good idea of what you're in for if you've never operated a model at these speeds. Stability is the key. Without stability, you end up with a lot of pieces.
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