Hello Everyone,
I've just ordered a few graupner CF props for future boat projects(1.6 in pitch each: 42mm, 45mm, and 47mm). They fit a 4mm shaft thread . I decided to see how the 42mm one would do with the BJ26. But the the BJ26 shaft has a shaft thread of 3mm. Is there any type of like prop adapter that I can use that'll fit the graupner prop on the 3mm shaft?

Hi Bob
Are you sure that the BJ has a 3mm threaded shaft? That seems a little too small. A 3mm to 4mm Threaded adapter isn't possible. Not enough meat to work with with the two sizes. I have tried.
It is possible to make a adapter to go from 3mm or 4mm up to 3/16" and use the many CF graupner and metal props with 3/16" hubs.
Could you tell us the prop numbers you ordered? Only some of the Graupner props are good for hi speed. n.h.schmidt

Did you order from offshores? If you did , talk to Steve V!

I carefully measured it in mm.

This is where I ordered the props from:
http://www.astecmodels.co.uk/product...election=props
Scroll down to the Graupner 1.6 pitch series. I ordered two 42mm props, two 45mm props, and two 47mm props.

I checked them out .No part numbers shown.I suppose they will work. I know what everybody I know wants. The K series is the best and most useful. Some can use the S series but the S props will not work well on all boats. The K series can be had in 4mm threaded and some in 3/16" drilled hub. n.h.schmidt

You can slip the brass sleve that's in the stock BJ prop out and use it in the same manner. That's what ProBoat did to be able to use the larger props. I bought some K&S engineering brass tubing with the same ID and OD so that I can make adapters for all those props. The brass sleve in the stock prop takes some convincing to get out (it's not glued it, just a good fit), and fits in the Graupner CF props just as well. I also have used these adapters in GrimRacer and Octura props with perfect success. I'll measure the OD and ID of the tubing tonight and report back. You can buy the tubing at most Hobby Lobby craft centers or your LHS. I would guess that, if you bought the same size, aluminum and copper or SS would work well.

Here's a message that I e-mailed to a buddy with a Blackjack a month ago when I measured the brass adapter sleeve:

Brass adapter sleeve in stock prop CAN be pushed out and placed into a 3/16" CF series prop. Fits perfectly. Brass sleeve is 3.0mm ID, 4.75mm OD. CF45 is on and perfect!!

I didn't measure the length of the tube however. I had several of the K&S Engineering "Odds and ends" tube assortments that I bought from Hobby Lobby. I wne through them until I found a tube that was the same dinensions, then used a small 2" Harbor Freight metal cut off saw to make some more of the adapters about the same size. They fit snug in a prop and don't require any glue.

There's an insert with the BJ's instruction manual that states that they changed the prop from what was originally used. My guess is that they had to use what prop was available, but their shaft was already too small, so they came up with the adapter to solve the problem.