Adding steps to a small inflatable

[Brandon]

Hello I currently own a 9'9" Quicksilver inflatable with an inflatable keel, I have been running a 15hp motor on it and it runs really well when there is a bit of texture on the water surface, however; when the surface is glassy it feels as if the boat slows and the motor runs harder...it almost seems as if there is some suction (which there very well could be) slowing the boat.
I have been daydreaming about making some stepped running pads that glue to the running surfaces of the pontoons and possibly the center of the hull in an effort to prevent this suction on smooth water as well as provide a faster ride all around.
It seems that the boat normally runs at about 20-25mph (guess), I am wondering if this would possibly do the trick to aerate the underside of the hull and eliminate that suction drag.

Thank you,
Brandon

[Willallison]

Because the bottom of the boat is not rigid, when you go faster the bottom of the boat develops a 'hook' in it. This will be particularly bad if the bottom isn't taught. Make sure that the tubes and in particular the keel are inflated as hard as you can get them. (Careful about leaving the boat out in the sun like this...)
If the bottom still isn't taught you can try adding a couple of wedges between the bottom and the transom (inside) to tighten things up.
Zodiac produced an inflatable some years back with smaller tubes located where the main tubes and bottom meet. This could be worth a try if you have access to someone who clould make them for you....

[Brandon]

Thanks a lot for your reply Will, and I will take your advice; however, I am also wondering if would be a waste of time to try and aerate the underside of this shallow draft hull with a few small steps similar to those found on some ski boats, I beleive that one particular company calls them LFIs (Laminar flow interruptors). Despite the relatively low operational speeds (20-30mph) it seems that getting the geometric bondary layer to separate and turn turbulent would still be beneficial and possibly provide a higher top end and better range. I have seen gemini inflatables produce some roll up inflatables with "highjacker tubes" attached to lift the hull out of the water at running speeds--it seems that it would benefit these small craft if the highjacker tubes were stepped somehow. Any thoughts?

Thanks, I really appreciate yours (or anybodies) interest,

Brandon

[Willallison]

There are those on this forum with far greater knowledge about steps than I, but I wouldn't have thought that at the speeds you're talking about any great benefit would be derived from their addition. But more to the point, unless you can ensure that the bottom surfaces remain straight - without developing a hook - than the addition of the steps would be a complete waste of time.

[Sealion]

I used to operate inflatable boats for the army. Although they had a stiff wooden keel below the floorboards, they also had another board hinged on the centerline, called the butterfly board situated in the last few feet before the transom underneath the keel to keep the flexible hull rigid. It was made of thin ply with the hinge made from the same material as the tubes. I could make and fit some highjacker tubes for you but unless they were big enough to lift your soggy bottom out of the water I doubt they would solve the problem, and you may have to get a longer legged motor or cut the transom down.