The big brown truck just made a visit

[marinesteam]

Just wanted to brag a bit on what the UPS man just delivered.

It's marked 18 24 Geo. E. Taylor St. Paul MN. It's quite the chunk of bronze. Should be perfect when I get a hull to put it on. I know I'm probably doing this backwards but the prop came up and you don't see these very often. This is the size that calculates out for a hull of the proportions that I have in mind so I decided that it would be best not to miss out on the opportunity. I have a very rough draft of an idea done up in Delftship for a 23' drake stern launch with a 6' beam though I'm toying with taking it down a few inches (5'6"???)

The prop is from an antique dealer in Vermont, To bad the history gets lost along the way, would have been really interesting to know where this was used originally. There are mentions of George Taylor being a member of the St Paul Motor boat club. This might be worth taking a look into at some time.

This month's issue of Wooden Boat mag arrived as well and flipping through is saw an article about Naptha launches. That should be a good read.

Ken

[fredrosse]

Such an Excellent Find, a real steamer prop in good condition! I collected about 30 propellers before building my steamboat, and then I built a sidewheeler!

[Lopez Mike]

I'm a light shade of green with envy. I bought an 18 x 24 recently but it has the usual large blade area typical of Michigan power boat wheels.

Mine was rather poorly packed in a cardboard box and one blade was peering out. The truck driver was concerned about damage. I laughed and deliberately dropped the whole thing on the lawn. I asked if it had attacked any other packages in the truck?

Anyone need an 18 x 20 LH? My friend found it while diving. The nut was a few feet away. A story there.

[gondolier88]

I'm probably doing this backwards but the prop came up and you don't see these very often. This is the size that calculates out for a hull of the proportions that I have in mind so I decided that it would be best not to miss out on the opportunity. I have a very rough draft of an idea done up in Delftship for a 23' drake stern launch with a 6' beam though I'm toying with taking it down a few inches (5'6"???)

Ken

I disagree Ken, it is so difficult to buy existing steam prop's for new builds it is now easier to buy a prop' and build a hull and engine to suit.

Your design sounds extremely beamy- almost 1:4 beam to length- 5'6" would be an improvement, it's width at waterline that really counts, but ideally you don't want a beam to length ration of anything less than 1:5 in a steam launch, 1:5.3 is a fair hull and 1:5.6 is a tender hull- of course that is a rule of thumb and there are always variations on the theme- if by drake stern you mean the same thing as a beaver tail stern then you will at least have maximum waterline length to play with. Going to be difficult to swing an 18" prop under a beaver tail (if it is the same thing you are describing) as they have a very flat run- perhaps making it a tunnel stern would be a way to keep draft low.

Congratulations on the beginnings of your boat!

Greg

[marinesteam]

Greg, Thanks for the compliment.

From what I understand, a Beavertail stern is different from a Drake stern in that the Beavertail is a continuous curve around the stern while the drake stern comes to an apex. The Beavertail also has a shallower angle to the waterline (flatter stern) The bits below the waterline are quite similar to each other and the compromise hull is as well. The lines of the Chequamegon hull are derived from a popular fantail and I'm targeting it's hydro numbers for the initial design criteria. The drake stern is inspired by as many photos as I can find of hulls of this style and then trying to derive the three dimensional shape. The prop will be about a foot and a half back from where the fantails prop was located, so this should help in placement somewhat. I think I do need to shallow out the area under the prop to get it a bit toward the water line. As I mentioned, still in the early phase to get proportions, especially the sheer lines, looking good. I have listed the hydros from the current iteration.


Design length 23.000 (ft)
Midship location 11.500 (ft)
Length over all 23.000 (ft)
Length on waterline 22.827 (ft)
Relative water density 1.025
Design beam 6.000 (ft)
Beam on waterline 5.173 (ft)
Maximum beam 6.229 (ft)
Entrance angle 17.673 (Degr.)
Design draft 1.521 (ft)
Waterplane area 78.299 (ft^2)
Moulded volume 48.662 (ft^3)
Total displaced volume 48.662 (ft^3)
Displacement 1.390 (tons)
Block coefficient 0.2319
Prismatic coefficient 0.5511
Vert. prismatic coefficient 0.4087
Wetted surface area 90.507 (ft^2)

[S. Weaver]

There is something about a prop leaning against the wall to keep one focused. Congratulations!

Just received my Wooden Boat too. The naptha article downplays steam launches - more out of ignorance than malice - but it was a fun read.

I like the lines of the dream.

[cyberbadger]

I bought an 18 x 24 recently but it has the usual large blade area typical of Michigan power boat wheels.

Can anyone give a plan/simple answer of why something very similar to what Mike is describing is not appropriate for a steam launch. - Or point me to a thread.

My current planned prop that I have:
Is and 18" diam x 24" pitch. 18x24. But it has large blades like mike is describing.

prop2.png (119.29 KiB) Viewed 9295 times

A short description of my launch: 24 ft modern aluminum pontoon boat hull, 6HP 1902 Toledo Steam Car engine. (If I get 6MPH I will be very happy, 4MPH I will be satisfied)

I would have thought for slower revs on a steam launch you'd want to have larger blade area - but my intuition clearly is wrong. I saw some posts about propellor haircuts.

Very Confused.

-CB

[Lopez Mike]

My simple (as in 'not so smart') understanding of the blade area issue is that having more area than you need for a given power just adds drag. Like having wide wings on a light airplane with a low powered engine.

The narrower a blade is for a given area, the more efficient it is. Sailplanes have long narrow wings.

The pedal powered water craft people use propellors that look like airplane props.

I would narrow my blades if I thought I wouldn't mess it up.

I suspect that the gains in this area might be relatively small compared to working on waste heat.

[S. Weaver]

It cries out for the 4.5" "portable mill" ...

[cyberbadger]

It cries out for the 4.5" "portable mill" ...

S. Weaver/Steve,

I was going to PM you but others may have the same question.

4.5" "portable mill" - I don't get this reference.... Hack saw?

-CB