frame work

[Patrick]

SST-60 Conversion

Jason,

Critical dimensions for an SST-60.

Tunnel width = 46" to 48"
Tunnel depth = 7" at transom frame
Sponson width = about 12" (along dihedral)
Sponson angle (dihedral) = about 9 to 10 degrees
Sponson length = 13 ft (approx)
Overall length = 14 ft min. including collapsible tips
Vertical motor board height to top of tunnel roof = 17"
Engine set-back (gearcase nose cone tip to sponson tip) = about 14 to 15"

If you can convert your SST-120 to the above dimensions using 7 frame members you have a winner.

Pat

[MN1]

Although the winning boats in SST 60 have the S tunnel bottom. Much different that what is working for SST 120 right now. The S bottom has been tried in SST 120 but has not been perfected. It could be that the speed is to high for this shape to work.
Mark

[JJJeffcoat]

this is what i have...

thanks for the dimensions Pat. i will be trying to apply them to the project. i think it would be neat to have a matching set of SST-60 plans. ive made a few modifications to the frame i had after all the input and want everyones opinion on this. 1st i dropped the top of the deck (on the outside top edge only) .5 inch to get a little bit of roll in the deck. 2nd i added the "grab rail" along the outside of the bow. approx 1" worth. 3rd ive added the second ply along the "skid plate". thought this would give extra grab in tight corners. so this is my Super Ram custom (updated). i may make the stringer along the top outside 1.25" instead of 1". what do you think?
i truly do appreciate everyone’s input.

oh yea, what do you mean by SST-60 "S" bottom?

[Patrick]

S-Bottom

The S-bottom is the shape of the tunnel roof. There are 3 basic designs...the "S-bottom", the "U-bottom" and the "flat" tunnel roof. The S-bottom was first introduced by Angelo Molinari back in the late 1960's and was quite revolutionary at the time.

If you picture the tunnel roof (side view) from the leading edge from the front moving towards the aft, the tunnel roof line takes the shape of a very slight "S" inthat the first 3 to 4 feet it has about a 1" hook (hedlund hook) also common in 3-point hydros and then flattens back out until about the last 2 feet where it gradually has about a 1/2" to 1" rise (relief) ending at the afterplane. The hook and relief are very gradual and progressive. The hook at the front allows the boat to capture "air" coming out of a turn and "pops" the boat up in a hurry (often referred to as how the boat carrys itself) exiting the turn. This packing of air is more critical to get the boat accelerate with lower HP engines such as SST-60 and SST-45. The relief at the aft of the tunnel roof creates overall lift, the more relief you put in, the more lift you generate. Think of the tunnel roof as an airfoil (wing) because that is what it actually is. This design in airfoils is often called a reflex trailing edge which has high lift characteristics.

One thing to remember is that the geometry of an S-shaped bottom is critical for overall performance and if a builder hits the design just right he is not going to share his good fortune with others. The "U-shape" bottom is a little simpler where the entire tunnel roof has a very slight "hook" beginning at the leading edge and ending towards the aft with the last 3 feet to the afterplane being flat (no relief). Works well if you get the geometry right.

Pat

[JJJeffcoat]

update

here are a few more screen captures of my updates. the model is looking really good. thanks for the infomation on the tunnel bottoms.

[JJJeffcoat]

here it is!

this is my final 3d model of the frame structural members. looking nice. i will start detailing all members after the model is finished. any remarks? i just wanted to thank everyone that has helped me along the way.

[JJJeffcoat]

still working on it..

here is the latest model

[JJJeffcoat]

and another

and other renderings

[JJJeffcoat]

would make

a great poster.

[JJJeffcoat]

update..

im about done with these drawings. been a looong long road. i really wanted to thank everyone again for the input and suggestions i did get. i got what i was after, a really nice set of blueprints of a SST-120 boat (11 pages). i will be building here soon. got to get a nice place to do it. i think i may try to take these plans and mold them into a SST-60 also if anyone is interested. good looking boat.
also, i did have a few posters made of the last post i made. they are 11x17 size, really deep color. its just an artsy kind of thing, but it looks really good. Also if anyone is interested in buying one, let me know.
thanks, Jason
JJJEFFCOAT@COMCAST.NET

[Lights]

Nice CAD work Jeff. What system are you using?

Mark

[JJJeffcoat]

also.. sst trailer

i also have a blueprinted tunnel boat single axel trailer if anyone is interested. im making the trailer part of my blueprints.
i am using AutoCad as my primary drafting platform. i know it well and can make it "do the walk"...

[JJJeffcoat]

shovel nose hydro rendering

here is another one of my projects. i think it turned out nice also.

[JJJeffcoat]

i think ive got my SST-120 prints about done...

im also about ready to start building. anyone out there want to do some trading? a set of my blueprints (13 full scale pages 24x36 size) for a gearcase or complete midsection? i would really like to make a deal with someone that has an extra powerhead too. that may be a bit of wishfull thinking but. if i can't trade into a deal maybe make a deal. ive got alot of hard work into these drawings and take alot of pride in my work. thanks for any input.
Jason

[JJJeffcoat]

for those interested

updating my design