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View Full Version : Interesting Sponson Mod



detox
08-29-2011, 04:26 PM
I have experimented with adding more AOA to my Whiplash 20. Using the higher powered p sport setup boat was very fast, but also very loose at the same time. Here is a different aproach that may help boat run faster and be stable also. Copied and pasted from Jim's Boat Dock.


I have received a few calls from people saying they can't get their Backlash over 65mph. 65mph isn't bad, but not up to par when expectations are in the low to mid 70's.
About a month and a half ago, Juice and Dale complained about the speed and hesitation of the backlash both in the straights and coming out of the corners. At first I just told them to test more, but after several trips to the lake with the same results, I finally told them to add angle of attack (AOA) to each shingle, as well as adding an additional shingle to the rear ride surface. Once they did this change, they instantly picked up 10-15mph and had excellent acceleration out of the turns.

The problem with increasing the AOA is it makes the boat looser, and I didn't know if the change would make the boat too loose in racing conditions. The first 3 races they went to the boat won each event, but the turnout was fairly low. The first real test was the Gas Clash, in which the boat finished 1st, 2nd and 3rd, solidifying my willingness to share what changes were made in case someone else is having problems.

For months I racked my brain trying to figure out why some of the boats are running in the mid to upper 70's, and some are 10mph off the pace and sluggish coming out of the corner. I knew how to fix the problem, but didn't know why it was happening until I spoke to Peter Muller last night. He told me that the reason this is happening is probably due to the fact some people use heavy weights to glue their sponson decks on. This downforce holds the skins to the framework as intended, but also pushes the framework down. Once the glue dries the sponson stays in that position, thus decreasing the overall angle of attack. What Peter said made perfect sense to me so I called some of the guys that are having problems, and some of the guys that are not having problems. The people who were having speed issues all used weight on the tips of the sponsons. The people who used tape or rubber bands did not have any issues with the boat. Ding ding ding!!!! Thanks Peter!

The Backlash is very much different than the Whiplash. We started from scratch, and changed everything about the sponsons. If the boat is built as intended, it works great, but to make the build process easier, we have decided to make the change to the kit.

If your boat is running above 70mph, there is no need to make this change, as it will not do much for you (Congratulations! You built your boat perfectly). It won’t hurt you, but probably isn’t necessary.

If you wish to make the change, here is what you have to do:
There are two shingles and a ride pad on each sponson. What I want you to do is make up some wedges the same width and length as the existing shingles. Sand them so the leading edge is zero, and the trailing edge is 1/16” and glue them in place over the existing shingle. So you are increasing the AOA by 1/16” on each shingle. The trailing edge step will be increased from 1/16” to 1/8”. On the ride pad, do the same thing as you did on the other two shingles. You will now have three shingles on each sponson, instead of two.

If you are in process of building your boat, you have two options:
1. Build the boat as is, but make sure you don’t add weight to the front sponson tips when gluing the sponson decking on. Your boat will run great.
2. If you want to make the change, you can increase the AOA of each shingle by sanding the 1/8” framework. Leave the trailing edge of each sponson strip alone and sand the framework so the leading edge is 1/16” deeper than what it was previously. See the attached picture. You will also have to sand the outside sheeting frames down 1/16” so that the leading edge of each shingle is flush with the outside bottom sheet (as the kit is without any changes).

We make every effort to make sure our designs are perfect prior to releasing them to the public. We pride ourselves with the amount of R&D we put into every boat. With the Backlash, we went thru all of the steps and didn’t see a reason why we shouldn’t release the boat. Our boat is exactly like the kit and it runs extremely well.

All kits from here on out will have the updated shingle AOA. The increased AOA will give you more flexibility during the build process. If you have questions, or don’t feel you can make the change, please let me know via email and I will help you out.

Thanks,

Brian Blazer
Blazer Marine

detox
08-29-2011, 04:28 PM
5876558764