Joe has good info for you. If you are wondering why the running surfaces are placed wider it is to improve stability in the corners.
As demonstrated in this wrecked boat.
mike,in the picture here,i see space between the riding pad and the turning point (outside angle) and the inside towards the tub.my pads are one flat section from tub to first turn angle towards the outside.was just wondering if the is any benifit between your design and mine? thanks for the insight. 25+ years and still trying to learn something new.mike.
I didn't build this boat. I think Scott Meyers did. I ended up with it when a club member became too ill to race anymore and I helped him sell his stuff.
To answer your question though I would assume it's more about the width and placement of the pad. I have had the most success with pads that are pretty close to 2 1/4" - 2 1/2" wide in boats that are in the 13-15 lb. range. My first boat was a Speedy that Ron Erickson built that weighed over 20 lbs with a K&B in it and it just sagged terribly in the turns until I added wider surfaces and Picco Bluehead to that tank and actually blew it over. I think my jaw hit my shoes when that happened. It also showed me that running surfaces also can pack air as well as the tunnel. One of the more successful guys here actually uses really deep recovery pads to block the air getting to the riding surfaces. If you were to see that boat on a set up board you would swear it would never work (his boats are also light, perfectly balanced with a really successful center section design as well). What I know is if this guy shows up he is most likely going home with the hardware.
My first Speedy was a total pig to drive. If you went left you just held your breath because it would spin or roll in a heartbeat. Having never driven any other boat I wasn't sure I could even do this because I was out of control half the time. Once John Logan built me a 15lb. boat with a Geraty/Nachweih sponson design I actually won the first race it ran in (albeit most the rest of the field was dead in the water). More to the point I had never even been in a final before that.
I only mention this because there seems to be a lot of guys who struggle in this hobby like I did initially and it's because they are trying to run boats that no one could drive. Of course while a basic design might be flawed there are also a lot of factors like weight distribution, strut and turn fin alignment, prop selection, ect. So if there are any new guys out there wanting to do this, get a boat with a proven design and not just buy the first POS you see on ebay (not to mention that the registration might already be taken). I have seen people squander a lot of money and bought themselves 15lbs. of grief that they could have spared themselves if they had just went to some races and asked questions of the people who were running well. I loaned a long-time club member and in the hobby generally for 30 years one of my boats yesterday and he had never driven a boat that stable, predictable or handled that well. Didn't even know a boat could be that easy to drive.
I wrote a lengthy article with lots of photos on rigging an 1/8th scale nitro boat that should be up on the Unlimited Northwest website in a little while. I will post a link on IW when it's there. Hopefully it will help more people be successful and want to keep doing this hobby. I am going to do other pieces on finishing and scale features, another on reassembly and initial set up and finally on testing.