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Nesting dinghy designed to plane under power?


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I gathered materials and was preparing to start construction on a new 10' nesting dinghy to replace our existing 8' one.  We want a bit more space for hauling supplies or when using it as a dive boat.  One thing we'd talked about was how it would be nice to have a bigger motor so we can plane under power, both to get places quicker and theoretically maybe even to save fuel doing so. Still need nesting as deck space for storage is limited on our 36' sailboat.

We have a 2 ph Honda for our existing Danny Greene design.  Chugs along fine, but of course no planing (though I swear that a couple of times with only one person and catching a following wave just right it sorta kinda thought about planing...for a few seconds). Our existing boat and the ones I've been looking at building (a Greene "Chameleon" or a Spindrift).  Was leaning toward the Spindrift initially, but the Greene design seems to fit a bit more boat volume into a slightly smaller nested footprint on deck, so am swinging back that way.  Still no final decision.

Both designers recommend 2-4HP engines.  Both are row, sail, and power.  We like the flexibility (though from past experience, we'd be willing to pass on the sailing if the trade-offs for other benefits seemed right).

Anyway, I had a sudden epiphany remember boat design articles mentioning problems designing hulls for safe turns on a plane.  Maybe my goal isn't as easy as a bigger engine.

Has anyone used one of these designs (or a similar one) with a big enough engine to plane?  If so, was it stable in turns?

How much engine power is needed?  

 

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1 hour ago, Bob Perry said:

Check out the PT 11 nester by Russel Browne. It does everything well.

http://www.ptwatercraft.com/ptwatercraft/Welcome.html

   I looked at the PT11 a while ago.  A VERY attractive boat, but concluded that the cost for a kit (approaching $5k) was too rich for my taste, and they don't sell plans, only kits.  I do plan on using a few of their components (like the clips for attaching the two halves).
 It would be nice to confirm that it works well on a plane and how much engine it takes to do so.

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Planing hulls are inherently differently shaped than rowing/low powered hulls. So yes you could throw a bit more power on the rowing boat (I strapped a 4 HP to my FB11) it won't plane, though you think it will... It goes faster to some degree but not much faster. Maybe 5 or 6 knots? It was stable enough in turns because --- it wasn't planing!

You can of course row a planing hull. But you won't enjoy it much. My GV10 dinghy could be rowed OK with long CF rowing oars (about 7-1/2' long I think) but the wide immersed transom meant a fair bit of drag.

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5 minutes ago, Grande Mastere Dreade said:

ok,  why are they called "nesting" dinghy's ?     nest on the cabin top?

they come apart in the middle and one section fits in the other to save space. go look at the PT11 page for a really beautiful example.

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9 hours ago, Zonker said:

Planing hulls are inherently differently shaped than rowing/low powered hulls. So yes you could throw a bit more power on the rowing boat (I strapped a 4 HP to my FB11) it won't plane, though you think it will... It goes faster to some degree but not much faster. Maybe 5 or 6 knots? It was stable enough in turns because --- it wasn't planing!

You can of course row a planing hull. But you won't enjoy it much. My GV10 dinghy could be rowed OK with long CF rowing oars (about 7-1/2' long I think) but the wide immersed transom meant a fair bit of drag.

"But mom, I want it all!"

Plus, of course, cheap and easy to build.

Oh yeah, and beautiful.

Meanwhile, back in 2020 reality, thanks for the info Zonker.  I was afraid that was the probable situation.  Was/am hoping someone has a design that straddles a bit better.  Haven't seen any "designed for planing, not displacement" nesting designs so far, though there are a bunch of the in non-nesting versions.  Wish it was as easy as cutting one in half, but I know they don't nest well by accident.

I'd really like to extend the "easy travel from the boat" range.  Of course, if cruising doesn't open up within a year or so...

Saw the dinghies you mentioned (bateau.com) and one of the descriptions for the Fast Boat versus Flat Boat designs did a good job of laying out the distinction.  They pretty much said that the rocker bottom of their displacement design just wasn't going to plane, while the flat bottom and immersed transom of their planing version wasn't going to row happily.  I'm assuming that with enough horsepower applied any dinghy design will plane (or sink from the outboard weight), but I can see where that could make for an excessively-exciting ride.  

Dang.

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How about long and skinny? Long and skinny doesn't need to plane to go reasonably fast.  And it could row acceptably. 

3 piece 16' that nests into <7' or so?  A sleek freighter canoe is sort of what I'm thinking. 10-14 knots maybe with a 8 or 9.9 HP?

Because it would be reasonably light it would float high with a 2-3 people in it, and thus the narrow not very deep transom isn't very draggy. 

I like this idea. Big and fast and wide isn't the only way to go.  

image.thumb.png.913907ab1ea5975834f593d887749f60.png

image.png.8fcbb78310f388840a3b95186284ee40.png

image.thumb.png.020146c74db372a37a9feddab2107bf1.png

 

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11 hours ago, Zonker said:

How about long and skinny? Long and skinny doesn't need to plane to go reasonably fast.  And it could row acceptably. 

3 piece 16' that nests into <7' or so?  A sleek freighter canoe is sort of what I'm thinking. 10-14 knots maybe with a 8 or 9.9 HP?

Because it would be reasonably light it would float high with a 2-3 people in it, and thus the narrow not very deep transom isn't very draggy. 

I like this idea. Big and fast and wide isn't the only way to go.  

image.thumb.png.913907ab1ea5975834f593d887749f60.png

image.png.8fcbb78310f388840a3b95186284ee40.png

image.thumb.png.020146c74db372a37a9feddab2107bf1.png

 

I'd want to change the color. That purple won't fly heah n de Souf.

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12 hours ago, Zonker said:

How about long and skinny? Long and skinny doesn't need to plane to go reasonably fast.  And it could row acceptably. 

3 piece 16' that nests into <7' or so?  A sleek freighter canoe is sort of what I'm thinking. 10-14 knots maybe with a 8 or 9.9 HP?

Because it would be reasonably light it would float high with a 2-3 people in it, and thus the narrow not very deep transom isn't very draggy. 

I like this idea. Big and fast and wide isn't the only way to go.  

image.thumb.png.913907ab1ea5975834f593d887749f60.png

image.png.8fcbb78310f388840a3b95186284ee40.png

image.thumb.png.020146c74db372a37a9feddab2107bf1.png

 

Sure!  A panga... I like it!

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I don't think you need one. Just don't do high speed turns!

 

Think of a 10' inflatable dinghy. Nice and stable because it's wide, and the tubes give more buoyancy as the boat heels.

The same amount of stability can be had by having a longer boat, with less beam. It's all about the overall amount of buoyancy as the boat heels.

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  • 4 weeks later...

 

On 9/23/2020 at 2:15 PM, Zonker said:

I don't think you need one. Just don't do high speed turns!

 

Think of a 10' inflatable dinghy. Nice and stable because it's wide, and the tubes give more buoyancy as the boat heels.

The same amount of stability can be had by having a longer boat, with less beam. It's all about the overall amount of buoyancy as the boat heels.

The ideas OK, but I don't have deck room to carry the kind of length that it looks like would be needed, even when three-part nested.

I had a sudden thought (always suspect).  How about a trim-tab-type setup that allowed one to change hull shape "enough"?  

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  Yeah some of the Vendee Globe boats tried that I think. 

Some of the problem is that a good rowing boat narrows toward the stern, as well as have a nice gentle rise of the buttocks.

Planing hulls are exactly different. No taper in plan view toward the stern and very flat buttocks aft. And an immersed transom at rest.

Really hard to change the shape enough to matter. We noticed in the San Blas, dugout canoes with horizontal trim tabs attached to the stern. These prevented squatting somewhat when the dugout was powered by a small outboard. But fixed of course because once you have an outboard on your dugout, you ain't paddling no more!

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The more I think about it, the more I think a good motoring dinghy is probably now our priority, with sailing and rowing a second.  That represents a large change in mindset for me, but your San Blas dugout comment sort of sparked the realization.  

Yes, we will need to be able to row, but wouldn't intend to do that for long distances.  Yes, we would like it to sail, but that would shift from the primary long-distance method of dinghy travel to mostly recreation, since a planing outboard dinghy would be so much faster.

But, of course, carrying the fuel...

Sigh.

Another random thought.  How about a nesting dinghy with two different stern halves.  One rowing/sailing and one planing outboard?  I wonder if creative design could result in one configuration giving a shorter overall length the the other, but resulting in a three-part nesting that doesn't take TOO much more space that a two-part?

Or, while I'm spewing random thoughts, since the planing hull is wider and flatter aft, how about a lightly-built "stern cone" that slides over the aft hull to fill it out to the planing shape.  If that was in maybe a two-piece (port and stb half) configuration, maybe it would then be able to tuck into the nested dinghy for storage.  The two pieces perhaps shaped of foam with a glass skin over the outside?  Wouldn't seem to need a lot of structure since the "internal" stern hull would carry the actual loads.  

I better stop...

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Bob P and I came up with this nester that might be of interest.

image.thumb.png.78459b7ad40539a5eef90c0502fb5c59.png

    The client looked at it and wanted it to handle more power so I took out one chine for more of a planing shape. Then the client wanted to cut holes in the topsides for some goofy rack mount that would let it be stowed on the back bumper of a RV and hinged up vertically so as to not interfere with the RV TOAD. I called it the TAILGATER but the client had made a half ass prototype of the rack mechanism that would have butchered what was a nice nesting dink. I'll look for the subsequent version.

 

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16 hours ago, Zonker said:

a good rowing boat narrows toward the stern, as well as have a nice gentle rise of the buttocks.

Planing hulls are exactly different. No taper in plan view toward the stern and very flat buttocks aft. And an immersed transom at rest.

Zonker, that was my laywoman's understanding of these things. But the LiteBoat range of rowing boats have hulls which are like a skinny version of the delta hull favoured by the Open classes of sailing boats: broad sterns.    See https://www.liteboat.com/recreational-rowing-boats

Is Liteboat really doing it all wrong?  Or is there more than one way of optimising a rowing boat?

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4 hours ago, Rasputin22 said:

Bob P and I came up with this nester that might be of interest.

image.thumb.png.78459b7ad40539a5eef90c0502fb5c59.png

    The client looked at it and wanted it to handle more power so I took out one chine for more of a planing shape. Then the client wanted to cut holes in the topsides for some goofy rack mount that would let it be stowed on the back bumper of a RV and hinged up vertically so as to not interfere with the RV TOAD. I called it the TAILGATER but the client had made a half ass prototype of the rack mechanism that would have butchered what was a nice nesting dink. I'll look for the subsequent version.

 

That’s pretty nice. 

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30 minutes ago, TwoLegged said:

 

Is Liteboat really doing it all wrong?  Or is there more than one way of optimising a rowing boat?

They are optimizing for stability not performance.

 

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3 hours ago, Raz'r said:

That’s pretty nice. 

Thanks Raz'r. I would want one. The next was was a step up from a rowing/power pram to a power/rowing pram. Russell Brown said some nice things about the designs and I begged him to sell me his nesting hardware kits but to no avail. A Torqeedo was a candidate. You can double the output of them by stepping up the voltage with a second battery. So a 4KW/8KW between the two versions. Still have the file in the dust bins of a hardrive somewhere so will look for the other version to share.

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1 hour ago, Rasputin22 said:

Thanks Raz'r. I would want one. The next was was a step up from a rowing/power pram to a power/rowing pram. Russell Brown said some nice things about the designs and I begged him to sell me his nesting hardware kits but to no avail. A Torqeedo was a candidate. You can double the output of them by stepping up the voltage with a second battery. So a 4KW/8KW between the two versions. Still have the file in the dust bins of a hardrive somewhere so will look for the other version to share.

You build the boat, I'll get you the hardware.. Oh wait, I'm out of it and the guy that machines the parts retired. Shit!

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Chris Morejohn has some skiff designs that might* be worth looking into. Here's one he designed/built as a do-it-all nester a couple decades ago: 

img_2756.jpg?w=600

A bit more info and a bunch more pics can be found here, and a video of it running at speed here on instagram. *Not sure he's got plans available for it, unfortunately, as it seems to have the versatility you're after. 

His current design, evolved a couple generations from the one above, but intended specifically for power (6-15hp), is the Turbot 16/14/12. Plans are available, and building in multiple pieces has been given at least some thought, though perhaps only as far as the last 2 to 4 of the full 16'. Regardless, it's left to the builder at this point, as far as I know.
img_9695-1.jpg?w=600

 

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6 hours ago, j 4 said:


A bit more info and a bunch more pics can be found here, and a video of it running at speed here on instagram. *Not sure he's got plans available for it, unfortunately, as it seems to have the versatility you're after. 

His current design, evolved a couple generations from the one above, but intended specifically for power (6-15hp), is the Turbot 16/14/12. Plans are available, and building in multiple pieces has been given at least some thought, though perhaps only as far as the last 2 to 4 of the full 16'. Regardless, it's left to the builder at this point, as far as I know.
img_9695-1.jpg?w=600

 

Dang, this guy ticked the boxes, especially for planing with low hp.

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On 10/17/2020 at 1:24 PM, Rasputin22 said:

Bob P and I came up with this nester that might be of interest.

image.thumb.png.78459b7ad40539a5eef90c0502fb5c59.png

    The client looked at it and wanted it to handle more power so I took out one chine for more of a planing shape. Then the client wanted to cut holes in the topsides for some goofy rack mount that would let it be stowed on the back bumper of a RV and hinged up vertically so as to not interfere with the RV TOAD. I called it the TAILGATER but the client had made a half ass prototype of the rack mechanism that would have butchered what was a nice nesting dink. I'll look for the subsequent version.

 

Ras, It's a nice looking dinghy.  Do you know how the "motor" version did in high speed turns?  That was the original issue I had raised at the top of this thread after reading of the problems with boats not designed for high speed turns sometimes tending to throw people out of the boat.  Apparently, some portion of the hull digs in and creates a sudden twist.

Heck, I'm not looking for the sudden loss of control part even if I stayed in the boat. :)

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21 hours ago, Russell Brown said:

You build the boat, I'll get you the hardware.. Oh wait, I'm out of it and the guy that machines the parts retired. Shit!

Oh no!  I wanted to buy several pieces of the connecting hardware to install in whatever I end up.  I really like the elegantly thought out engineering in the PT boats.  I had thought seriously about getting one, but my pockets just aren't deep enough.

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15 hours ago, j 4 said:

Chris Morejohn has some skiff designs that might* be worth looking into. Here's one he designed/built as a do-it-all nester a couple decades ago: 

img_2756.jpg?w=600

A bit more info and a bunch more pics can be found here, and a video of it running at speed here on instagram. *Not sure he's got plans available for it, unfortunately, as it seems to have the versatility you're after. 

His current design, evolved a couple generations from the one above, but intended specifically for power (6-15hp), is the Turbot 16/14/12. Plans are available, and building in multiple pieces has been given at least some thought, though perhaps only as far as the last 2 to 4 of the full 16'. Regardless, it's left to the builder at this point, as far as I know.

Nice looking, but all are bigger than I can accommodate on my smallish 36, even if they were nesting.

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8 hours ago, IStream said:

I have a dockmate with the F-RIB. He's not thrilled with it. If you're seriously considering it, I'll try to get the details.

I'd be interested.  I like RIBs in general, just couldn't figure how to carry one.  I'd like to stay in about a 4.5' by 5-ish' rectangle (though I can bulge a bit here and there).

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4 hours ago, Raz'r said:

What about the Spindrift line?

available in cnc kit

Actually, that is the boat I was intending to build originally (though I think I'll have to stay with the 10' version).  It may well still end up being the one.  I already bought the plywood for it and have swapped emails with the Spindrift people as I tried to figure out whether I could squeeze an 11' version on my deck.  The beam is a problem.
   I also like Danny Greene's 10' nester.

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20 minutes ago, SVArcturus said:

I'd be interested.  I like RIBs in general, just couldn't figure how to carry one.  I'd like to stay in about a 4.5' by 5-ish' rectangle (though I can bulge a bit here and there).

I'll pick his brain the next time I see him. 

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21 hours ago, SVArcturus said:

I'd be interested.  I like RIBs in general, just couldn't figure how to carry one.  I'd like to stay in about a 4.5' by 5-ish' rectangle (though I can bulge a bit here and there).

OK, for something completely different. Rolls up into a smallish container. I checked with the Wash State distributer, $1900 for the 340/11 footer.

inflatable tubes roll up to just 23kg and fit into a bag 1.2m x 0.4m x 0.3m. The total weight with floor and transom is 36kg with a load capacity of 515kg.

 

https://www.takacat.com/340-lx-inflatable-portable-boat

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14 minutes ago, IStream said:

I seriously considered the Takacat until I asked the distributor about dog claws on the air floor and he got very hesitant.

Owning a race boat with limited space it's pretty attractive. 

There's a big step up in engine weight between the 6hp and the 8/9.9 HP engines, but the distributor said the 6hp won't have the grunt to get it moving. The 6hp would likely get one of the nesting skiffs to boogie nicely, at least with just 2 folks.

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19 hours ago, Raz'r said:

OK, for something completely different. Rolls up into a smallish container. I checked with the Wash State distributer, $1900 for the 340/11 footer.

inflatable tubes roll up to just 23kg and fit into a bag 1.2m x 0.4m x 0.3m. The total weight with floor and transom is 36kg with a load capacity of 515kg.

https://www.takacat.com/340-lx-inflatable-portable-boat

That does hold some attraction.  All the inflatables sort of "fake" the length in that a foot or two is aft of the transom to keep the outboard above water. So the interior space in an 11' inflatable is sort of a 9' rigid dinghy.  
Hmmm.  Got some good points.  Gonna look harder at this one...

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On 10/18/2020 at 1:13 PM, Russell Brown said:

You build the boat, I'll get you the hardware.. Oh wait, I'm out of it and the guy that machines the parts retired. Shit!

Lot of machinists out there. Can't say I've ever seen a decent pic of what you sell but given that and some rough dimensions I'd be very surprised if I couldn't machine them myself if I were so inclined.

FKT

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  • 2 months later...
On 10/18/2020 at 4:59 PM, IStream said:
On 10/18/2020 at 4:38 PM, SVArcturus said:

I'd be interested.  I like RIBs in general, just couldn't figure how to carry one.  I'd like to stay in about a 4.5' by 5-ish' rectangle (though I can bulge a bit here and there).

I'll pick his brain the next time I see him. 

Okay, I finally bumped into my neighbor and asked all about his F-Rib. Turns out his complaints are fairly minor:

1. The west coast distributor had no stock when he wanted to buy and they couldn't tell him when new stock was going to come in

2. The east coast distributor sold him a boat but couldn't supply him with an origin cert so he couldn't register it. The west coast rep helped him get one.

3. The oarlocks are far enough outboard that they can scrape up the mothership when you come up alongside.

4. The factory transom flapper valve leaks.

5. The air valves are weird.

All that said, he loves how it holds air, needing a refill only about once a year if you don't deflate it. It's very light and performs well with a small Torqueedo (though it won't plane without more power). It folds up very small.

On balance, he's actually pretty happy with it. 

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On 9/23/2020 at 11:15 AM, Zonker said:

I don't think you need one. Just don't do high speed turns!

 

Think of a 10' inflatable dinghy. Nice and stable because it's wide, and the tubes give more buoyancy as the boat heels.

The same amount of stability can be had by having a longer boat, with less beam. It's all about the overall amount of buoyancy as the boat heels.

An inflatable proa might work- think a Catapult-ish approach.  Easier to store in the lazarette.  Strap it all on a paddle...

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 A bit unpopular at the dinghy dock but otherwise a good idea. But if I draw 16'x~3' beam boat I can have similar stability to a 10'x4.5 beam rib was the point I was trying to make

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2 hours ago, IStream said:

Okay, I finally bumped into my neighbor and asked all about his F-Rib. Turns out his complaints are fairly minor:

Thanks iStream, those are very interesting.

I looked at their six offerings (foldablerib.com) and they have some pretty nice looking boats that do store very small.  Maybe a bit heavy and they need some deck space since it looks like they have to be inflated before launching.  The smallest 8.5' one was 79 lb.  However, storing it in a <3' x 3'x 1.5' space is pretty great.

I really liked the look of the big 15 ft model and can store it in my available space (needs 4.5' x 3.5' x 1.5'), but 160 lbs is substantial for handling on deck. Any of them would probably require a good hoisting launch-and-retrieve setup for use as a tender.   They definitely store compactly.  

It appeared that when planing a good portion of the inflatable tubes remain in the water.  Is that the norm for regular RIBs?  I was thinking they were planing mostly on the rigid bottom.  These seem to have a somewhat flatter bottom than regular RIBs, which I guess is sort of needed to fit into a small storage space.  Maybe not an easily driven hull.  Saw 20 hp motors on some of them in their videos.

They were pretty pricey (and I was thinking that even before I saw the 20% British VAT tax that is added onto the list price). The smallest is $2,995 and the largest $5,350...PLUS 20% VAT.

More of those damn pros and cons...

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11 minutes ago, SVArcturus said:

 

It appeared that when planing a good portion of the inflatable tubes remain in the water.  Is that the norm for regular RIBs?  I was thinking they were planing mostly on the rigid bottom.  These seem to have a somewhat flatter bottom than regular RIBs...

Suspect with the flatish bottom you want the tubes to engage the water for comfort.

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