new mono

[hydro guy]

im building a new O mono and im building it with a step(not O legal) but still fun....my question was, is there a good way to build the step into the hull? im building with balsa and ply.

[K.R.Joye]

Most wood mono designs use horizontal bulkheads strategicly positioned help form the hull shape. If you know where you want the steps to begin and end place bulkheads at these positions.You can use the one bulkhead as the beginning of the step and another for the back wall of the step.Steps shouldn't be `added on wedges' they should incorporated into the flow of the bottom surface to keep the hull light as possible.

[hydro guy]

thank for the reply....yeah i would never add wedges....thats just obvious...to me anyways. but i couldnt wait any longer so i started building, im almost done, the step came out PERFECTLY. the boat is set up for O class, its 23 inches long and about 7 inches wide. its all balsa at this point with a 1/32 ply doubler on the transom, im thinkin i might sheet the step with 1/64 ply to make a strong sharp surface. the step is about 8 1/2 inches forward of the transom and runs all the way back to the transom. so far she looks promising, but i dont know if it will handle 8 cells and the mega mini 4 i have, so i may just have to run 6 cells and a d4 or something similar. ill try and get pics as soon as possible

[Reed Eagle]

HydroGuy,

I think that you will need more than 1/32" ply for the transom doubler. I would go for a minimum of 1/8", preferably 3/16" thick ply.

So us some pic's if you get a chance. Sounds neat !.

Just my 2 cents.

Reed Eagle

[hydro guy]

yeah i kind of had the idea it moght not be enough....but the transom is 1/8 balsa, should i sheet BOTH sides with 1/32? or do you think that 1/8 balsa and 1/32 could suffice.

[hydro guy]

i might as well touch on set up now....i have never run a stepped mono like this, for anyone who has experience....here is my question, where is the cg on boats like this usually, i would suspect it may be different than a conventional mono...? also should i have the shaft running parallel with what WOULD have been the keel if it wasnt stepped? also should i try to get it to ride without the forward portion of the boat touching, just on the aft portion of the step. or should i try to get it to ride on a little of the step and a little of the transom?

i plan to use a mega mini 4 and 8 matched 2400's. i was thinking a x432, x435 or x632

[vicman]

Check the pic here Step hull bottom (http://www.rumrunnerracing.com/feforums/attachment.php?s=&postid=12547). This is what the step should look like or similar. As far as CG goes, it should be behind the step if it is in the right place, (8in sounds good). The boat should ride like a hydro if you want the best speed out of it, but usually it will ride with the rear of the step in the water and the transom just barely touching the water at the edge at full SAW speed. This is how they were origianally designed. Multiple steps just give you more points of contact for stability and to eliminate bouncing on the transom. Your 1/8balsa @ 1/32ply transom would probably be better if it were a sandwich of 1/32ply-1/8balsa-1/32ply. I usually use epoxy and baking soda(gap filler) to laminate these peices together. If you adjust the CG like you would on a 3point hydro, 1/2 to 2 inches behind the step as a static setup and play with from there you should be able to get it to ride right. the reason that it is such a wide range is because it will depend on overall weight as to how it will react. Too far forward and it will bounce too much, too far back and it wont try to get out of the water at all and slow it down. You also want to adjust the rudder so it doesnt push up in the turns, this makes it a little spin out bad.
With the power you plan to use I would try the x432 first or maybe even a 1630 and go up from there.

vicman

[hydro guy]

hey thanks everyone for the replies....thats what mine looks like minus the strakes and mine isnt that deep of a vee, but its the same which i assume is a good thing. ha ha ha. ill try what you suggested about setup....one thing...wouldnt a 1630 be better suited for a hydro? or would it work good cause it would raise the trasom so it only rides on the step? if thats the case then could it be a 1732? cause i have a few 17 series props. how do i adjust the rudder so it doesnt push? make less throw?

also another thing....the hardware i made would put the prop about 3 inches bacl from the transom...on a stepped mono should this be more or less? and also...where should the rudder be?

[vicman]

Well I suggested the 1630 cause it has more pitch (and lift) but less diameter so it would spin up more. The 1700's may do very well, you'll have to try and see. Remember that more pitch means more stress on the motor. Yes this is a "Hydro" prop but has worked well on stepped monos for the same reason you mentioned as long as the boat is set up correctly with the CG in the right place. You might have a cavitation problem with the 1700 series props on takeoff, maybe in turns as well, try it and see first if you already have them. The prop being 3 inches back will be good, especially for a high pitch prop as the 1700's. I would put the rudder behind the prop about 3/4" to 1-1/4" inches, or you could put it to the right of the prop so the leading edge of the prop is at or in front of the leading edge of the rudder. As for rudder adjustment, if its angled back (top forward more than bottom >\) it will raise the back of the boat, if its angled forward (bottom forward more than top >/)it will cause the back of the boat to dig in or drop ito the water. You want it so when its on plane and turning the rudder is slightly angled forward or straight up and down. This is only what has worked for me, others may have different or better ways depending on the CG they choose.

vicman