I have a Sweet Sixteen with a 415sbc motown motor hooked to a blackhawk surface drive. Boat runs mid 80's but starts to handle poorly getting into the high 70's into the 80's. The x dim. is low by an inch. Was considering adding a pad to the bottom to increase my x and give me something to ride on other then the rounded keel. What would be the best material to build this up. What coring, resin, and fiber weight. Looking at a pad to be notched at the transom 6-8" and be about 10" wide run 6' 6" forward and be 1.5" deep. Any thoughts and recommedations? Would it be worth the work, and would it benifit in the handling dept?

I have a round keel on my 20 cig, everyone i have ever spoken with concerning the 2 diff keels says the round is better. you would be better off either raising the x or putting on a box that raises it.

How long a trim tab you running.JOHN SR

I have 20" tabs on and they are hell. If they touch above 75 she gets realy wild. And wild is feeling god with his hand on the shoulder sayin that should doooooooo! Don't forget that the 20 cig has some more hull to ride on. The 18 with the same x and less power will hang with me the only difference I see is extra length. I won't raise the engine to go any higher due to moding the hatch and back seat. I want the top side of the hull to look stock. So my route is box or pad and the pad give me the x and a true surface to run on. So many fast smaller boats running on the delta pad. What effects will the box have on a short boat? Have a look http://www.youtube.com/watch?v=AvlT3...qw-E16W_4RHknT

I noticed the video was uploaded by craig, are those the props i sold him? honestly then i would try the box and put it back some and that will change the cog when you are running wfo, putting it further back is going to lower the x dim, but hopefully it will keep more of the wetted running surface in the water.

Yes that is Craig. Stearn lift is the issue that is putting the boat into the wobble. As you can see in the vid it is running nose up which is great less resistance in the air then the water. There is very little trim in use. I have had 4 engine and drive packages in the boat and the terminal velocity is about 72-73mph the bh pushes that to 78-80. As the boat speeds up it lift completly out of the water. I think that because the boat is so short and the tendancy of the bh to stern lift it has greater impact on the handling vers a longer boat. Even with a raised box of 3" and putting the drive back 12" more. Would that really be a true increase of 3" of the drive in relation to the water comming off the back of the boat? With a pad there has been some testing in the 80's on a 100+ 16 and I have conversed with the gentleman and the pad was what got him his resaults. Removed the ill handling of the 80+ speeds. When I replaced the stringers and transom in the boat I raised the drivetrain as high as I could to keep the boat stock on the deck. If I went the 3" box route I have no room to go up with the motor and I don't want to run a box with u-joints on the flywheel with no coupler. The dim. of the pad are that of the 100+ 16 from the 80's. What would be the best materials to build this up with for an 80+ mph beating. Would it be best to buildup with a foam core, or wood, and laminate with 1700 glass, fair and shoot on some gel? Or buildup totaly with glass, filler, and poly or vynl resin and then gel?

check with some of the donzi guys on donzi.net. but from the video, it appears to me that you are overpowering it and not having stern lift, but the bow is high but keeps dropping, if it were sternlift, wouldnt the bow be plowing?.just me but before i would try modifying the bottom i would try to space it back.

No dought that the boat is overpowered. As I get into higher speeds the boat feels like it gets on the forward keel and starts the wiggles and gets violent, no driving through it. In the vid I'm running close to 80 but have to get out of it due to some rouge waves. I wonder if the increase in x is worth the time and money, weather it be the box , pad,or modding to raise the engine. http://www.youtube.com/watch?v=tKFdmf5i4Ow

after watching the vid I would spcae the drive back, imco box or its..what prop are you running? maybe too much bite?

I always wanted to build a pad on my Baron/Powerquest 185 after riding in an early 80s Scarab 1 with the pad.
I liked the way the boat did not want to ever chine walk as it had the nice flat surface instead of the rounded keel to ride on. The ride was firmer for sure .
I think a high density foam shaped and vacuum bagged to the bottom with thickened epoxy would be a start and than laminate over that with 1708 and and more epoxy with a finish of fairing compound and paint it after words.
Vinylester might be the better product to use as than you can gelcoat instead of paint the mod . Glass Dave is the man to ask.

What i have always toyed with is what if you stepped the pad with like 5 steps.Long as you live through the mods you could always grind it off and change it.