Had the boat out to day. Very disappointing 31775 RPM at 60MPH with a H7. Still don't have a handle on the set up. Had to run the strut 1/8" higher than the rear sponsons to get it on pipe. Took some tongue out of the prop and also reduced it. The H4 hooks up with the strut lower but no speed.
If I put the strut the way you have it in the pic. It won't get on pipe. What's the trick. Have the rear sponsons at 1/16 above the board.
Well Got more props to try. Keeping my hopes up that it will all come together.
David
You need it to have a real good set up overall (engine, pipe & boat) before you can use a H7 on a Kep's freebie. The H4 or H6 is more like it before you have it going really, really well.
Can you take a photo of its side view (also the complete boat) so I can have a look?
Have you built it 100% as the plans or made any modifications?
See the attachment & give me the measurements and we'll go from there.
/Niklas
Niklas
I had redone the rear sponsons last night so the mesurements are diffrent than what I ran it with last.
Hear is what I have
A 1832 g.
B 503 g.
C .685"
D .665"
E 1.620"
F 1.540"
G.665"
H 1.5 AOA
I have tried to build as close to plans as I can.
Thanks for the help
David
If the "C" height is .685 (17.4 mm) then the "D" height should be around .787" (20 mm). There is a kick-up on the bottom of the tub from the rear most engine bulkheads towards the transom that is 3 mm high. So the starting point of the AoA of the tub is having its middle flat part level with the water then the rear height should be 3 mm more then the belly height.
The strut should sit on its rear most tip so to speak with an AoA of around 1 deg.
When you have adjusted the rear height you must re-adjust your front sponson AoA also.
Then I would set the rear lowest sponson tips at 17.5 mm depth with at least 1.5 deg AoA - try them with a higher AoA if you think they want to suck the rear down.
I noticed also that the drive dog sits almost all the way forward to the strut... Are you using a normal clamping engine coupler? If so there needs to be a 1/8-3/16" gap there.
The depth of the rudder we use is 45 mm below the rear sponsons - that looks a bit deeper.
The rudder weight is not too bad but these boats just runner better with them lighter in the butt (loading the engine/prop less) - there is quite alot of hardware on that tail that you can make lighter - try aiming for less then 480 g (16.9oz). Move the batterypack forward etc.
/Niklas
Ok the tub should be level and the rear sponsons should touch the board? Right now I have the rear sponsons about .100 above the board with the tub level. The mesurments are showing this as they were taken with the boat flat on the board.
I am using a square drive set up no gap on drive dog.
I also have the data loger and GPS on board about 3oz.
This is were I am confused. The tub level should the sponsons touch the board and should the strut touch the board.
Setting up the front I under stand But I need to get the back straight first right?
David
The tub level would mean when the strut at its set-up angle (about negative 1 deg) is resting at its rear most point on the set up board with the front sponons tops set up level. That equals to rear height over set-up board 3 mm higher then the belly height.
The rear sponsons should be set at about minus 2.5 mm of the rear height (D)... Egualling the same height over the set-up board...
#1. Set the belly height first at around 17 mm.
#2, Set the rear strut AoA of about 1 deg negative.
#3. Set rear strut height @ belly height (#1) + 3 mm.
#4, Set front left sponson flat top part to be level.
#5. Set front right sponson to be slitghtly nose-up vs the left sponson.
#6. Re-check and adjust the earlier points.
#7. Set the rear sponson height to 2.5 mm above set up board and at 1.5 deg AoA (or slightly more - not less anyway).
Thats the basic set-up.
Make shure the running surfaces are completely flat... Check again. I mean completely - not almost flat.
That should put it in the ball park
if the rudder weight is less then 480 gr.
