Saving Old Seagulls

Ive been interested in the reasons for the differences in the shape, .....

Me too!

Jon

H-A has just suggested trying 123Dcatch has anyone tried it?
For the database pictures.

I had a quick look at it....
Are you wanting to turn the pictures into a 3d thing or just be able to add cad thing to them and scale the photo?
If you just want to add cad bits and scale the photo I can do that with the 2d cad I have got.

The Hydrofan prop design was probably a Way-Hope idea in the early to mid 1960's, as this more efficient blade profile produced a higher thrust than the previous round blades on the same motor, it was considered a cost effective performance upgrade over earlier props & many 50's motors were up graded.

They fell out of favour during the Japanese seaweed problems in the 1970's that forced the development of the weed free props, that many Seagull racers feel don't perform as well in weedless waters.

AJ is probably the man to talk about this as he's probably in the middle of testing for his Bass Strait crossing, & has access to warm water, sunshine, both styles of prop, a rev counter & a GPS, so should be able to provide you with definitive answers.

AJ how's your testing going?

Hope to get the boat in the water in two weeks. am buffing up a couple of hydrofans for the WSCP's but will also run a couple of 102's with different props as comparison. Fairing the boat has taken way too much time but I am finally down to the last few coats. Picking up the 150 Litre fuel tank today.
AJ

Interesting work on this thanks all.
I always liked the traditional 5 bladed 11 " Hydrofan fitted to the Silver Century Plus models in the 70s - lots of thrust at low rpm. Using the Longliner at Springs on the Fowey after periods of heavy rain up on the Moor means one encounters loads of floating junk and debris on the ebb, so I fitted one Silver Century Plus with the (semi) weedless round bladed prop. It copes reasonably well with weed etc where the Hydrofan is hopeless but in a direct comparison between the two designs the weed shedding one is inferior for thrust and boatspeed - so think I may go back to two Hydrofans - if one engine clogs I can start the other!

Robin

Hi, I just found this thread, and have been doing some work with photogrammetry and building 3d models - this involves taking lots of photos, and then using software to generate a 3d model and clean it up. I currently only have a 40 minus, and silver century fan prop. Here is an example what can be done.
https://skfb.ly/PFq7
https://skfb.ly/PFqy

That is cool stuff.
I wonder if the file could be used for CNC work?

Not sure about CNC, but can definitely be used for 3d printing and therefore metal casting.

Where on the blade do I measure or calculate pitch ?[attachment=0]1- 050.jpg[/attachment]

This is one simple way that I found on youtube.

https://www.youtube.com/watch?v=Uzv_m_Gm1es

Until recently I had never seen or heard of a trolling prop for a century, the first one I saw was at a boat jumble and an old friend explained to me what it was, then one popped up on eBay, poorly described, I grabbed it just for its collecability, it's NOS and it's definitely for a century with 100 cast into it even though it looks a little 40-ish.
For those not familiar with trolling props, they have a small surface area making them inefficient, it means you can go really slow and still have the motor at reasonable revs so the water still circulates and doesn't foul up the plug, great idea but not many about.

Never seen one like that before, thanks for sharing.

It looks like 4 knifes!

I think it was made like that to cut the line as you drive over it!!

You'll probably need to design a standardized "jig" so that the camera is the same distance above the gauge sheet or slight differences in "apparent" dimaeter will creep in and get people running off down dead ends looking for props that are a poofteenth larger than their apparently identical one.

Maybe see what differnef it makes shooting from 1 ft, 2 ft, 3 ft above prop on flat surface, see if any difference in diameter is perceptible?