Got a good sporty question..

[T.S.Davis]

......well, I think it is.

On my monos, I try to get my weight as low and centered in the boat as I can. The boat rides on the the keel. The lower your CG is in the boat the less influence it has laterally. Makes them more stable IMO. Ever have a rogue wave lay your boat over for a nice hook? Get your CG lower.

Got me to thinking. What about sport hydros? We all just jam the cells in the tub next to the motor, on each side of the flex, or sometimes ahead of the motor. We shoot for balanced. Good enough right? As long as the CG is right front to back we stop thinking about it. But.......but......but.....sport hydros don't ride on the center line. Has anyone ever experimented with moving the weight out away from the center line of the boat? Like cells in the sponsons.......ish?

I feel like moving the weight out would make them less prone to the sponson dance. The UL might benefit from this approach. I know it makes a difference in a cat.

BTW I have no hard evidence either way. Just wanted to see if anyone else had some thoughts on it.

So.........thoughts?

[properchopper]

I build my monos with the batteries inside the rails for that very reason.

When early on began experimenting with ways of taming the death dance on the UL-1 I in fact did move the batteries as far outboard as possible. No discernable improvement. Altering the AoA did the trick. That's all I got.
:smile:

88900 88901

[Fluid]

Mono-master John Finch preaches that the vertical CG in a mono should be high, this to keep the vee boat laid over in turns. I have tried the CG high, even adding weight above the chines to achieve it. Now I prefer to keep the packs centered between the stringers - that helps to better secure them in a flip too.

Some UL-1 drivers report that increasing the lateral polar moment - moving the weight out towards the sponsons - helps in keeping hydros from doing the sponson dance. While I have tried putting the packs in the sponsons, all my hydros in the past five years have the packs between the stringers. I notice no disadvantage, but that may be due to hull design.

Most of my cats have had the packs on the tunnel for two decades. This was proven an advantage in cornering years ago, at least with the guys I hung out with. We ran a KeyWest O-Hydro class (round cells) indoors, with a triangular course featuring two very tight (135*) turns. With six-boat heats it was high adrenaline racing, believe me. The guys who built their boats with the cells on the tunnel consistantly finished the heats upright, the guys with the sponson-mounted packs did not. We all changed to on-the-tunnel packs, and never looked back. Counter-intuative yes, but it worked.

That's my experience anyway.


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[T.S.Davis]

Jay, that does conflict with my thinking. My PB cats like the cells low in the sponsons. Could be that a Key is a special animal. Dennis used to run his cells on the tub too. I doubt there's ever been one faster. Drove like a slot car too. Although, PAGS runs his Sprint with the cells on the tub. That thing is stupid straight or turning. Doesn't matter.

I wonder about Johns boats. I have no reason to debate his expertise. The Wildthing design is still my favorite mono ever. Does he have the weight to size ratio that we do? I wonder if he still feels that way at the speeds we can run now. For me, I just want that thing running straight at 60 mph without the bobble.

All my sports have had the cells in the center too. Chatter hasn't been an issue thus far but I've been running Whips for years now. Chatter proof.

I have a brand new PT at the house to put together and thought I would toss around some out of the box think'n. I had planned to make some changes to it to make it my own but I can't find anything I hate about it. haha Not enough to butcher it at least. The design seems sound and it's realtively attractive. We have so many PT's in our club I gotta do something to it. Maybe It will just be cosmetic changes.

I have seen a little bit of chatter on some (only some) of the PT hulls but I don't think I've seen the new version run yet. All but one of ours are the old version that have a touch too much lift and need weight in the tips. I suppose it's possible that the added weight being wide (at the tips) is actually making them chatter. Object in motion tends to stay in motion.........but that would hold true for the boat at speed too. Mass times velocity equals linear momentum. Blabbing myself into a circle.

Maybe if it's really rough......... center the weight but if it's only mildly rough........ weight at the edges?

Can't get my brain around this one. Overthinking it.

[Fluid]

As far as mono chine walking goes, this quote is from John Finch, and while he is speaking about a specific nitro mono (so the exact dimensions quoted may not apply here), this is the best single description of chine walking and its cures I've seen. And it works in practice too, I've cured most of my club members' chine walking problems by following John's advice.


"The further back the prop the higher it must be out of the water to let the transom of the boat settle into the water for control. So raise the strut and prop. If you shorten the strut an inch that will help too, but cut an inch off the trim tabs too. If the prop is off to the right or left of centerline the boat will be lifted on that side as well, and that starts to control the boat half way down the straightaway when the boat is easily influenced by the lift of the prop. At slower speeds and acceleration you don't see the problem because the boat is not yet balancing on the prop. The turn fins are not the problem because you don't see the problem when accelerating. The centerline of the strut should be about 5/8ths of an inch above the transom vee when the prop is about 3 to 4 inches from the transom to get good control. It is imperative that the prop be centered unless the rudder causes lift when the boat airs out. If the rudder lifts the right side of the boat then you can shift the prop to the left of centerline to compensate for rudder lift. Deeper rudders cause more lift. Keep in mind all these little things don't have much effect at average speeds, but if you get the boat aired out and going fast they then become your tuning devices." John Finch



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[madmikepags]

Terry just for correction I run my cells in the sponsons in My SC

[Southwest]

Ok gentlemen; i used to have 4 pages of John Finch on setting up a mono and i have a couple of his books and my question is where can i find those 4 pages of mono setups. I looked on google and alot of duplication stuff there, no luck, thanks.

[BHChieftain]

I tried putting the packs on my 1/10 shovelnose out towards the sponsons and I found the boat was not able to settle and it make the sponson shaking worse as it rode over rough water. When I put the packs towards the centerline, the sponsons bounce much faster and seems to stabilize better. I currently run the packs next to each other centerline, but slightly biased to the side with the turn fin (for me that is the right side as my 1/10 is set up for RHT-- I got that tip from Classic Hydro setup page).

Chief