progress of DES.

theres a sure fire way to overdrive there..

Looks like you have a real good start, good luck.

HAL......
What are you planning to use for the prop shaft?
What kind of bearings?
I would also try to find a thrust bearing to help take the load off the mount and get more usable rpm's on the shaft.
You may also want to consider some kind of bracing (horizontal-from front brace to rear brace) to connect the sides of the upright mounts. The thrust of the prop will want to push the rear upright forward, causing binding on the shaft.
But then I'm sure you already thought of this

Looks very good so far.[8D]

Looks Good, nice low CoG

Looks GREAT ! Hats off to you !
( now ... finish her up so we can see the finshed project and "hopefully" buy one from ya ! )

Just curious ... what ratio you have on the gearing ? 1 : 1 1 : 1.5 ? or ?
( not that it matters all that much since props will be used to make adjustments to the change of power/speed . )
Again ...
VERY NICE ... keep us posted on updates !

Got to doing a little more on it. Had my first experience with a lathe, needless to say it took a couple of shafts to get it right. And first with a milling machine, to set the bearings.just wish my bit was a little smaller to get a better fit. But in the future, I will have them done by a real machinist. Tomorrow, I'm planing to set the engine. Then set the stand in the boat, then the fun part deciding on how to install the rudders and roll cage.

For now the gearing ratio is 1:1, it could be changed simply, by changing one of the pulleys. With a different ratio, a lager prop could be used, giving more control of the boat.

SUPER DUPER ! ! ! When you get her set in , please take some pics for us to see . [8D]

just bench tested. I need to make a shaft with left hand threads, or find a better way to lock the prop nut and starter cone. It looks as if the belt is going to hold up for a while, but I will be trying belts made from different material.
Thinking about drilling and tapping the nuts in place. The prop can be drilled and pinned, because I have a nut on both sides of the prop. Any ideas??

Got the nuts fixxed, I drilled and tapped and installed a set screw. Now something else has come to make me a little concerned, with the prop behind the engine, not enough air is passing around the engine to keep it cool. But this is just from running it on the bench, may be in the boat it might be different??

doing more bench testing. With every thing in line and true, it works great. But I got to thinking about, the times that "something goes wrong" and for what ever reason the boat is out of control, flips or hit something. The DES gets bent of line a little. What would happen?? So I set up the timing pulleys out of line, so that the belt is binding a little, and I set one timing pulley rubbing against the frame, to make it harder for the engine to turn the prop. Result, the belt did not hold up. Keeping in mind that the frame is made out of 3/8" aluminum, it will take a hard flip or crash to bend it(it can happen). The belt that I used is very light weight and cheap. Back to work, on the next set up, I have several things I will be trying. Then after(and I will) I get every thing working so that the worry of the belt breaking, out in the middle of the lake, is no longer a big issue, I will make a package for you guys that are wanting one.

GREAT ... very glad to see your getting all the bugs , and possible bugs , worked out of her .
Oh yeah .... and better make sure I'm on your list (LOL)
Hey , are you making these a "universal" hookup , or for what specific engines ?

Trying to cover every thing, that may go wrong. After all of the bugs are gone, I will make it adjustable to match up different engines(may be???) and I will make the belt tention adjustable. I'm also looking at installing rubber buttons, to help with the vibration.
Terbobob you're at the top of the list.

[8D] [8D] [8D]

Brown nosing again are we ??????

Hal, PM me a price to think about..........

LOL ... nope ...
Conversion of symbols to words :

[8D] ( cool ) [8D] ( real cool ) [8D] SUPER cool ( oh yeah ! )



LOL

Hey guys still researching. I think I've came up with a better idea, at least for the nitro engines. Working on a mount that does not use a belt, after I get the plans together and do a little more searching and thinking, I'll post a drawing.
For the gassers, I'm working on them also, but its going to take a little more work.

Ok ... good deal ... keep us updated when you can .

Haljmac,
I really look like a beginner for sure!! Looks really nice!!

Just an idea...you mentionned working on something for gassers...what about using the flex drive to drive the pusher prop, with the engine still mounted low for a low CG??? Could make use of most of a weed eater hardware??? What do you think?

I think it will work if you would fix sothing on the shaft to hold it in place on the prop side of the flex. I have a pic on the post airboat challenge, see if that is what you are thinking about.

I'm not sure about the cable being able to take the amount of load that the prop would put out. On an inboard hull, the props are very small compared to an airplane prop. The shafts are relatively short and no deep or sharp angles are used. Keeping the shaft properly lubricated would also be an issue. Though it may be possible, imo, not very practical.

Now, a solid shaft and beefy u-joint or cvd type joint........????

1/4" shaft on 5hp marine engine spinning a prop through water at 26,000rpm's is one hell of a load. Keeping in mind that the props on a airboat are bigger in diameter turning 18,000, but air does not have near the friction as water. I have shafts on a couple of my boats that are over 18".
The shaft would have to be set up in a stuffing box. The ends could be sealed with fuel tubing holding grease on the shaft.
One problem that comes to mind would be where to set up the radio system?
Now if you was running the shaft, and happen to hit the prop on lets say the wifes prize bush, then may be the shaft would torque up, but I beleave the prop would break before the shaft.
This would be cheaper than setting up a belt or gear.
It may also play with the CG. As for the problems that will araise, IMO they would be small, and easy to over come.

One MAIN thing to think about here with a lowered weedie and a using a flex/stuffing tube .
To get the height required for the prop , and considering the CG also needed for that motor , we are talking about some mighty strong angles ( bends in the stuffing tuve ) here ? .
For example - take a 36 inch boat . And say the CG is dead center . then consider the distance to the rear - 18 inches . Now , subtract at least six inches from that . ( why ? for the flex to have at least a straight run from the motor and to the prop of at least an inch and a half . and then the prop mount will have to be on the hull which also means that there is less/more room needed which will be about the additional 3 to 4 inches . ) Now take into consideration that you will need to RAISE up at least 9 to 10 inches in height , which of course , will require two bends , at that short distance , and that height , we are talking about some mighty strong angles here . And anybody that runs water propelled boats using flex cables , knows that the stuffing tube needs as little of a bend as possible , otherwise , not only do you decrease the output power of the motor to the final drive ( prop ) , but you also create a LOT of stress on both the flex and stuffing tube and or liner , which is a GREAT start for binding and snapping of the flex .
The solid shaft with u joints or cvd , would be a much better idea , I think .
Simply take a flex that you might have laying around and just try it and see what I mean ( of course , without the stuffing tube and what-nots , just compare and bend the flex to the required/needed bends.
This is just IMO .