advantages of a surface drive?

Nice website Chris. Appreciate you sharing your candid and honest experience. Great details on the site on your conversion too.

 

advantage of surface drive

the top half of the prop mimics the bottom half. as an example, a twenty in. pitch prop travels ( less slip ) forward though the water twenty inches in one
revolution. both the top and bottom. in a surface drive you can theoretically double the pitch using the same h.p.
i say theoretically because in order to plane you need to introduce your exaust right in front of the top of your prop. my Mans have ten in. exhausts plus 2.5 in.
idle relief ports in the transom.

 

I am not sure if Arneson came first but I have read an article that the guys racing the formula boats with big outboards noticed that the boat went faster when the props were partially out of the water. So they all set their engine mounts so that only half of the propeller is submerged.

 

rxcomposite,
I have been retired since 2004 but I was formerly the largest shareholder of Compsys. I logged 35,000 hrs. at the helm, 40yrs, and lots of design and building.
It seems to me I've learned more about boats since retiring than in all the time before, but with the abundance of opinions on botes ( like politics ) I would sound very windy if I tried to explain how all the experience one goes through changes even your own subject reality.
Trimax drives don't trim.
You wouldn't want to trim one.
Look at the FBMIL50 which is used by almost all spec. ops.
Just by luck I bought the only prototype that was on sale for the engines.
Spec. ops wants more.
So....................

It is a stable, faster, easier to drive and better boat.
The drive angle and the cleavers surface the entire stern and the boat runs on the first step's outer downturned tips at the chine.

It is a hydroplane not a deep vee.
Hydros ran 300mph back in the fifties.

Don't try to buy my boat!

 

milespm,

I am not selling any voodo dolls nor i am buying your boat. Please read carefully. It is not MY OPINION or experience.

 

The top part of the prop is /should be out of the water. How is it mimicking the bottom

Exhaust does not necessarily have to vent the prop but on deep props you will but depends on the boat its not written in stone.

 

Exaggeration is not acceptable in a technical discussion.

http://www.russwicks.com/hydroplanes.htm

This propeller driven guy took the world record in 2000 at only 221 MPH.

I guess they were faster in the 50's

 

hydros

Sir Donald Cambell drove "Bluebird" just over three hundred prior to losing
his life on a lake in South Australia in the late fifties.
I apologize but was only pointing out a stability issue similar to a three wheel vehicle with the two wheels in front vs. th4 rear. Special forces chose the hydro stance that did not fly the bow.
I don't appreciate being called out for this.
I won't be on this site again.

 

Milespm quote
Sir Donald Cambell drove "Bluebird" just over three hundred prior to losing
his life on a lake in South Australia in the late fifties.
I apologize but was only pointing out a stability issue similar to a three wheel vehicle with the two wheels in front vs. th4 rear. Special forces chose the hydro stance that did not fly the bow.
I don't appreciate being called out for this.
I won't be on this site again.
Reply With Quote




Bluebird was a jet not a surface propeller.

Sir Donald Cambel died in Bluebird in the 60's His father also died in a speed attempt in a boat named Blubird in 1951 at only 170MPH. Both attempts were on Lake Coniston in North England.

But you were very close with south Australia.

Don't go, stick around, I love your stories.

EDIT

Don't feel too bad, here you go I gone and got you this.

http://en.wikipedia.org/wiki/Donald_Campbell

 

frosty

you are a very rude man. I rely on memory not the internet. I have alzheimer.
Stories don;t interest me. i have contributed structural parts to hundreds of thousands of boats and the goal was always to try to improve them.
Your sarcasm improves nothing.
please don't reply

 

miles
what did compsys do?

PS the Campbells did land speed attempts in South Australia so easy to confuse that one if your not an Aussie

 

Im sorry but I will reply. My mission is not to be rude there is no such thing as an intimidator only the intimidated. I have not asked you to leave, on the contrary I have asked you to stay but if you have come here to impress with your experience then some accuracy is required.

We all have a life of boats to tell, we all want to shout to the world we know this and that and have been at the top of the tree, the states is not the only place to have a boat.

There are some extremely professional people on here and if you want to contribute, starting with your resume wont cut it.

You started by explaining what pitch is!!!!!!

Both you and I will be cut down if your not accurate where accuracy is required.

But what will not happen is we sit at your feet wide eyed listening to bull.

As far as internet is concerned no one here takes a quote form anyone without a link to back it up.

Rest assured that any thing you say will be taken down and used in evidence against you with a quick google, Thats the level of this forum.


Now stop your bottom lip from wobbling and tell us something we don't know.

 

Milespm, don't mind Frosty's sarcasm. Most of the people on this site are good people.

 

Can you please explain the top mimicing the bottom.

Theoretically increase pitch? anything can be theoreticall.

Please explain

 

pitch

when a submerged prop turns one revolution it pushes the vessel forward the amount of the pitch less slip which is often around 30%.
It takes h.p. for each of the prop blades to push that water but they all have
identical pitch and are pushing water at the same rate.
surface props use only the portion of the prop in the water and use less h.p.,
but the blades in the water are pushing at the same rate of pitch.