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Dingy home made flotation tubes... your input...

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zeil
Master Marine Consultant

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Canada
1314 Posts

Initially Posted - 03/18/2012 : 19:30:43

It has been our desire to add stability to our unruly, small, tippy but light weight 7.6 ft Back Water "Someday Baby". In shape it is similar to a "Walker Bay" but smaller.

We really like the little dingy apart from dumping people,

for its lightweight, rides before the mast, tows very easily and with the home-made cover provides extra storage for bulky items.

We have considered Walker Bay add-on tubes but beside being pricey they do not fit.

To come up with an economical solution we have thought of using standard thin-wall PVC 6" pipe about 5ft long and mounted somehow to both sides. The idea is to shape the pipe to the hull, include a wood reenforcing strip to the inside of the pipe and to the inside of dingy wall and fill pipe's cavity entirely with closed cell foam.

Each tube would provide about 3.14x(7.5x7.5)x150 c/m= 26.6 ltr x 2.2 lbs= 58 lbs floatation...

would that be considered sufficient floatation?

My question is... what method would you suggest I use to shape, bend and form the 6" (15 c/m) PVC sewer pipe to conform to the shape of the hull..

How would you suggest I fasten it to the hull...

What method would you use to bend, shape this 6" pipe to the hull

To add more floatation I could use a 90 degree and and connect a 6" pipe across the stern, leaving a space to mount an 3.5 hp ourboard

The tube is suspended at about the right location.

Top view

Float across the stern connected with 90 and flattened in the center to allow mounting of an small outboard motor...

Henk & Johanna
"Floating", a few off your "barnacles".
"Someday Lady" '95 C250WB #151 ('03 - 2016)
"Sea ya" 30ft Bayliner (04-2018 - 09-2018)
"Mariah" '96 C250WB #191 (05-2019 - 15-05-2023)
"Lady J" '00 C250WK #499 (05-2021 - 09-2022)

Edited by - zeil on 03/18/2012 19:54:03

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 03/19/2012 : 02:03:55

You should be able to heat and bend the pipes. Here's a site I found that explains how to do it http://billpentz.com/woodworking/cyclone/pvc.cfm. He's only working with 4" diameter but maybe it'll scale up to your size.

I don't know of a glue that'd let you bond a strip of wood into the inside of the tube, but maybe a heavy aluminum strip could be drilled & tapped from the outside and through the dinghy's skin that would allow you to bolt it to the sides of the boat? You'd want to stagger them vertically so you wouldn't create a hinge joint, but I don't know how practical that'd be. Maybe you could through bolt it instead? That way there'd be no need for the internal reinforcing plate. Actually you might be able to do your bends using the through bolts to pull it into place. Run car exhaust through the pipe to soften it, and tighten the bolts till its where you like it, then a splash with the hose to set it in place.

A bit of math shows you'd have about 2 cubic feet of space between the 5' lengths of pipe 2x(3.14 x 3^2" x 60" / 12^3). Using 2lb/cuft foam (60 lb flotation / cuft) that's about 115+ lbs of flotation total.

Edited by - delliottg on 03/19/2012 02:41:11

JimGo
Admiral

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USA
962 Posts

Response Posted - 03/19/2012 : 06:25:53

Have you considered "just" strapping pool noodles to the sides? I'm just making this up as I go along, but a couple of eye bolts on the sides of the dinghy would let you run cord or straps around the noodles and secure them to the dinghy. The noodles could be removed/replaced easily, too.

If you go with the PVC, I'd be concerned about developing a crack in the PVC and filling up the pipe with water. I would consider filling the space with a foam (e.g., pool noodles, spray foam, etc.) to help ensure you have enough floatation when you need it. You might also consider a bracket attached to the PVC that hangs over the side of the dinghie, with clamp-like mechanisms to hold it in place. That would allow you to easily remove the floats for service, storage, etc.

Edited by - on

Ape-X
Admiral

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USA
662 Posts

Response Posted - 03/19/2012 : 06:33:48

is the flange at the top rail strong enough to support the flotation? Use a bracket on the PVC that is secured to prevent rotation, and the flange as a vertical stop.

For stability, if you move the PVC further outboard, then stability is further improved. Think outrigger canoe. A couple of spars (that could be adjustable in for storage, out for stability) and voila

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 03/19/2012 : 06:57:17

Ape-x I was thinking similar, but moving the spars outwards would make it difficult to board from teh boat.

My thought was to rivet the tubes to a plywood backboard, then glass it over to look a little less like tubes riveted to plywood, and bolt the whole thing onto teh boat.

Edited by - on

JimGo
Admiral

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USA
962 Posts

Response Posted - 03/19/2012 : 06:58:57

I missed the float at the stern. I'd consider breaking that into two pieces, and mounting the outboard to the transom (assuming the boat is designed for an outboard). You shouldn't need too large of an opening between the pieces, so I think you'll still get 90+% of the flotation that you'd have had with the full float. As with the side floats, I'd look for something removable.

Edited by - on

Sam001
Vice Commodore

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USA
441 Posts

Response Posted - 03/19/2012 : 07:01:07

It seems that the "several pool noddles" idea would be quick and easy if that fits the "look" you want.

Edited by - on

redeye
Master Marine Consultant

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3476 Posts

Response Posted - 03/19/2012 : 09:35:10

Outriggers on one side.

Go Hawaiian Man...

ie...

http://homepages.paradise.net.nz/garyd/ulua.html

Edited by - redeye on 03/19/2012 09:37:08

TakeFive
Master Marine Consultant

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2272 Posts

Response Posted - 03/19/2012 : 10:17:03

What is your objective of doing this?

1. If you want to stabilize against tipping, you will want the flotation in the water at all times, but that will induce significant drag, especially with the blunt end caps that you show.

2. If you want it for additional emergency flotation, you may want it up out of the water. But remember that the flotation does not become "active" until it's submerged. If you put it too high, close to the gunwale, it may be of limited use, because by the time the boat is low enough to activate the floation, ordinary chop or a boat's wake could breach the gunwale.

Sorry to sound like a naysayer, but the problem with this retrofit is that with a boat this small, the difference #1 and #2 is maybe 6".

It may be that the safest way to add flotation is to add it to passengers and/or cargo - or to add the suggested outriggers with smaller, more streamlined flotation. When you extend it out like that, a little flotation provides a lot more righting moment (much as with a bulb at the end of a deep keel).

Edited by - TakeFive on 03/19/2012 10:18:26

Davy J
Master Marine Consultant

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USA
1511 Posts

Response Posted - 03/19/2012 : 11:23:23

I sold my hard dink and got an inflatable. But here is something that may work for you. I have these things mounted on my dock pilings. They are somewhat pliable, filled with air, and would probably conform to the shape of the hull.

of course they are not as inexpensive as PVC pipes:

http://www.overtons.com/modperl/product/details.cgi?pdesc=Dockmate-Piling-Post-Bumper& i=79966

Edited by - on

Tomas Kruska
Admiral

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Czech Republic
522 Posts

Response Posted - 03/19/2012 : 13:43:43

Hm... what about big fenders then?

Edited by - on

Voyager
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USA
5368 Posts

Response Posted - 03/19/2012 : 16:45:49

I have a double outrigger that connects to the gunwales of my canoe. It consists of a square aluminum tube stock (thwart) with extenders that connects under the lip of the gunwales and extends out about 2 ft connecting to a pair of 10" diameter x 24" long foam noodles mounted on vertical struts that can be adjusted up and down.
A friend refers to them as "training wheels" I keep them out of the water but if the boat tips the outrigger will stop the capsize. I can literally stand up in the boat and cast with my fishing pole.
You could recreate this configuration with tubes and PVC pipes. Would the thwarts interfere with your feet in the boat?

Thinking outside the box, have you considered finding an inflatable you could fit you hard dink inside of? That would give you the best of both!

Edited by - on

zeil
Master Marine Consultant

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Canada
1314 Posts

Response Posted - 03/19/2012 : 19:47:31

Thank you guys for all your ideas, comments and input... makes me seriously re-think and re-consider the project. In fact I probably should go and buy a small lightweight dingy, the West Marine type, but... "Someday Baby", has been with us through so many adventures that I hate to discard it for its only weak point of dumping people

Inbred qualities:
Is lightweight at a mere 45 lbs
Tows, planes and rides easily and handles well in rough seas
Fits perfectly between the stanchions up on the bow
Fits and trailers securely before the mast
With its tarp cover provides extra storage space for bulky items
Single-handedly loading it onto the deck while on the trailer
Single-handedly loading it onto the deck while in the water
Unsinkable and up-side down kids use it as a diving platform
Love its hard bottom when beaching on a rocky shore
Dumps people with glee every time

Besides.. it is just fun to experiment, request you guys assistance, make something out of basic materials and just fiddle around in anticipation of the new season.

Tried this afternoon to heat the 6" diameter according to the recommendation provided by David using a heat gun. Blowing the hot air through the inside of the pipe while taping a small hole on the other end, it'll only allow to "rubberize" a small section of the pipe and ran into trouble trying to form the pipe to the shape of the hull… So… we'll have to rethink this process and find a way to "rubberize the full length to the shape and bend of the hull. Perhaps by turning the boat on its side and "melting", the pipe on top of it.

Thought about your suggestions of using various sizes of noodles, installation of an outrigger, use big fenders, piling post bumper… all those suggestions have some merit but… if i just could get this to work…

After lunch Johanna came up with the idea of fabricating PVC tubes to the shape of the dingy's hull from left-over dingy tarp material. So… we set out this afternoon pursuing that avenue.. Copied the shape of the hull with a piece of plywood, made a paper pattern and copied it onto the PVC material ready to be cut out in a top and bottom section. This will be sewn together into a tube with a 4" diameter close to the bow and a 10" diameter one foot past the stern. Johanna's plan is to sew it together inside out with a reenforcing strip at the location of a teak wood strip inside the tube. The 1x2 wood strip should hold the bolts for mounting he tube to the side of the dingy Then pull it like a pillow case right side out and voila. Challenges to be solved are:
1) how the finish the ends of the tubes
2) how to install inside the tube a 1x3 wood mounting rail
3) how to fill the inside of the tubes entirely and evenly with closed cell foam or would it be possible to use bean bag pellets and stuff it full..
4) method of attaching the tubes to the side of the dingy
5) method to make the tubes height adjustable by say 3 to 6 inch

Lots of unknowns at this point

Your input, ideas, suggestions in or out of the box are much appreciated... please keep them coming...

Heat gun at work... only a 1-2 ft will get "rubberized" question remains as to how can one shape this to conform to the hull's shape

Opposite end of tube nearly closed to capture the heat...

New trial... making PVC tubes to fit the hull. Shape will be from 4" on the bow to 10" at the stern. Johanna is cutting a pattern

Top view of hull on plywood and tubes pattern shape

Tubes top & bottom shape

Edited by - on

JimGo
Admiral

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USA
962 Posts

Response Posted - 03/19/2012 : 20:25:52

Fill it with spray foam - the stuff you use to insulate around windows.

Edited by - on

zeil
Master Marine Consultant

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Canada
1314 Posts

Response Posted - 03/21/2012 : 12:38:22

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Fill it with spray foam - the stuff you use to insulate around windows.<hr height="1" noshade id="quote"></blockquote id="quote">

Before sewing and filling the tubes with foam we want to research methods of attaching the tubes securely to the sides of the dingy.

It would be preferable to somehow easily attach and remove the floatation/stabilizing tubes.

Any suggestions, ideas, concepts, examples in or out of the box...??

Edited by - on

JimGo
Admiral

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USA
962 Posts

Response Posted - 03/21/2012 : 13:04:40

C clamps that permanently attach to the tubes (e.g., drill a hole in the head of the C clamp and use that to attach the clamp to the tube). Or put eye bolts into the side of the dingy, eye bolts in matching locations on the sides of the tubes, and slip a bolt and washer(s) through the overlapping eyes.

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 03/21/2012 : 13:09:09

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by zeil
 Any suggestions, ideas, concepts, examples in or out of the box...??<hr height="1" noshade id="quote"></blockquote id="quote">

[url="http://www.ghboats.com/options/accessories/flotation-collars/"]Dinghy Dogs[/url]

From the website...

Simple installation requires only seconds to remove or replace. A small channel is bonded to the boat at the waterline, and the tube clips into this channel. Then the tube is fastened to cleats fore and aft.

Edited by - on

Prospector
Master Marine Consultant

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Canada
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Response Posted - 03/21/2012 : 13:53:10

Henk - what if you attempted removeable outriggers?

A pair of pipe clamps on each gunwhale, and the outrigger attached to the end of poles. The crossbars could be hollow tubes, bigger on one end than the other to allow you to adjust "outness" or draw them in by telescoping the tubes, or remove them altogether. A set-screw through the pipe clamp could hold the crossbars in place.

Set them outboard for boarding, inboard for rowing, detach and stow in/under the dinghy on the bow.

Edited by - on

Sam001
Vice Commodore

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USA
441 Posts

Response Posted - 03/21/2012 : 14:29:48

I thought the dinghy dogs were pricey at $495.
at the web page

Edited by - on

zeil
Master Marine Consultant

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Canada
1314 Posts

Response Posted - 03/25/2012 : 19:47:49

Thank you for your responses... we still would like to pursue floatation tubes rather than an outrigger at this point. However if our attempt fails we'll give it a try... seems from your description easily done.

Using C clamps or using eye bolts would work by adding a 1x2 strip to the inside of the tube to make attachments.

However, perhaps the simplest solution of adding and removing the tubes seems as shown in the Dingy Dogs photo's by sewing a 16" wide flap to the center section of the floatation tube and secure this with a round fitting into a c channel bolted to the side of dingy. Both tube ends of the floatation tube to be secured with lines/flaps to cleats.
Agree that the Dingy Dogs as shown seem a bit pricey...

Due to "spring yard work", and things around the house the project has suffered a bit of a delay...

Edited by - on

zeil
Master Marine Consultant

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Canada
1314 Posts

Response Posted - 04/02/2012 : 20:38:43

After some other activities we finally were able to continue with our floatation tube project... here's an activity update...

Johanna behind her sewing machine sewing the two tubes halves together. We've chosen extra strong UV stabilized awnings thread and using a leather needle for the job

Bought some Kwik Foam and experimented by filling a plastic bag... 48 hours later the foam never solidified. Beside this the weight would be a problem and would need far to many tubes... discarded the idea quickly and replaced it by using Polystyrene beads commonly used in "beanbags".

Once the tubes were sewn together we made a 2" thick cedar end cap glued into the tube and finished with the same material.

The end of the tube is scored and glued over top

Using a funnel Polystyrene beads are poured into the tube from the the smaller bow end of the tube.

A 1x2 is holding the tube straight and using a funnel Polystyrene beads are poured into the bag

Once the tube is filled we used plastic lunch bags to continue filling the tube and to apply pressure filling the tube...

About 60-70% of the 100 ltr bg is used... this translates into about 65x2=130 lbs displacement if fully submerged. Plenty for stability for our petit "Someday Baby"

Approximate location of the tube... note: we will glue a 1" strip over all sewn joints to make the tubes waterproof

Stern view of the floatation tube

The tube fits nicely inside the dingy for traveling and long distance towing if required.

Stern view of the floatation tube inside the dingy.

Next part of the project will be to fasten the tube bow, center and stern. This is still a bit of a challenge and we're searching for ideas. At this point I'm planning to use an outer schedule 40 PVC pipe with a slot cut into it allowing the sewn-on flap to be fastened around a smaller pipe and inserted in the the larger outer pipe. If this works we can simply slide the material into the tube, fasten bow and stern and voila ready to go... However if you have ideas or suggestions please let us know...

Edited by - on

JimGo
Admiral

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USA
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Response Posted - 04/03/2012 : 05:46:43

I really like the use of the poly balls - great idea! This looks like it will be a GREAT DIY project when it's done.

What about sewing sail slides onto the side of the inflation tubes and letting that slide through the groove in the PVC pipe?

Edited by - on

John Russell
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Response Posted - 04/03/2012 : 09:57:56

I think I understan what will hold it to the hull but, what will prevent it from simply floating on top of the water next to the gunwale? In other words, what holds it down?

Edited by - on

zeil
Master Marine Consultant

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Canada
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Response Posted - 04/03/2012 : 20:01:58

<blockquote id="quote">quote:<hr height="1" noshade id="quote">I think I understand what will hold it to the hull but, what will prevent it from simply floating on top of the water next to the gunwale? In other words, what holds it down?<hr height="1" noshade id="quote"></blockquote id="quote">

That's the question John that I assumed from the "Dingy Dogs", illustration provided but was not sure... so... I spent the better part of today experimenting various alternate methods. Finally I did end up trying to attach the sewn on flap at about center distance between the top of the gunwale and assumed water level. Sure enough upwards pressure on the tube tightens the flap, pressing the tube to the gunwale. With bow and stern fastened the tube, because of its shape, is unable to rotate and provides the wanted buoyancy without moving upward...

It seems simple enough but my next challenge is to find/make 4 11/4" SS C clamps with a 11/2" long bolt and 1/4 thread to fit around the PVC pipe to be bolted through the hull with wood blocking on the inside. Two clamps could be full 11/4" round and will act as a stop. The larger PVC pipe is to allow the smaller 1" PVC pipe with the flap glued to it to be inserted and held in place. Some basic testing shows that the 11/4 PVC pipe seems strong enough to withstand the pull.

By leaving the smaller bow end of the tube open, I was able to stuff another 4 small lunch bags filled with Polystyrene beads down the tube taking out a few more wrinkles.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">I really like the use of the poly balls - great idea! This looks like it will be a GREAT DIY project when it's done.<hr height="1" noshade id="quote"></blockquote id="quote">

The total weight of one tube, without a couple of nuts, bolts and PVC pipe is a very desirable 5 lbs...

Edited by - on

JohnP
Master Marine Consultant

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1520 Posts

Response Posted - 04/03/2012 : 20:21:15

Two comments:
1. I worry about the main failure mode for your tubes that are filled with polystyrene beads, that is, puncture by a sharp rock, shell, or stick!

Perhaps a simpler filler would be "packing bubbles" which will not escape if the outer skin of the tube is breached. They weigh nothing and cost very little.

2. The design of the attachment for the "dinghy dog" seems to be a really good idea, and apparently has adequate strength to hold the flotation tubes down against the weight of crew leaning to one side. You could easily duplicate that design by using a 12" long, 1" PVC pipe and slicing a 1/2" or 1/4" sector out of one side of it, smoothing the edges, and sliding in a 1/2" dowel sewn into the end of a 12" long 1" wide flap built into the hull-facing side of the flotation tube.

Attaching the 1" PVC tube (called the "track" on the dinghy dog) to the hull could be by several through-bolts or by some kind of adhesive, or both, as in the "dinghy dog" design.

Here's that description from the "dinghy dog" website:
Attach tubes to boat:

Dinghy Dogs covers have a flap sewn to the middle which has a special rod sewn into the edge. This rod is slid into a PVC track permanently affixed to the boat 10" down from the rail. The track is held to the boat with 1/2" stainless screws and 3M VHB™ double coated industrial grade acrylic foam tape with super high bond adhesive: .025" thick, 800kg/m3 foam density, 160 lbs./sq." tensile.

Tube length: 84"
Track length: 12"
Tube Diameter: 10.5" inflated.


I am surprised that the "dinghy dog" is just an air bag! I think that my suggestion of filling with packing "bubbles" is a sensible improvement for added reliability. If the tubes are punctured, then essentially no flotation would be sacrificed, and only minor water ingress would occur, since the almost the whole inside of each tube is filled with these watertight packing materials. They are attached to each other and would not escape through a small or a moderate gash that could occur, and the tubes would be ok until repairs could be made to the skin.

The disadvantage of using packing bubbles as filler is the bulk of the tubes, that cannot be deflated like the "dinghy dog" devices can. But if you store them in your dinghy, then that's not an issue.

Edited by - on

zeil
Master Marine Consultant

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Canada
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Response Posted - 04/03/2012 : 21:46:11

John: Thank you for your comments, information and suggestions

<blockquote id="quote">quote:<hr height="1" noshade id="quote">I worry about the main failure mode for your tubes that are filled with polystyrene beads, that is, puncture by a sharp rock, shell, or stick!<hr height="1" noshade id="quote"></blockquote id="quote">

Yes... that will remain an area of concern not unlike air-filled tubes except this will spit white beads rather than air bubbles in the event a tube puncture. However, the last 4 or so feet, are stuffed from the tapered bow end of the tube with small zippered lunch-bags filled with beads in order to be able to hand-push and compress the beads to maximum stuffed capacity. We found that this works well for compression which brings me to your suggestion...

<blockquote id="quote">quote:<hr height="1" noshade id="quote">I think that my suggestion of filling with packing "bubbles" is a sensible improvement for added reliability. If the tubes are punctured, then essentially no flotation would be sacrificed, and only minor water ingress would occur, since the almost the whole inside of each tube is filled with these watertight packing materials. They are attached to each other and would not escape through a small or a moderate gash that could occur, and the tubes would be ok until repairs could be made to the skin. <hr height="1" noshade id="quote"></blockquote id="quote">

Yes... it would be ideal tube filling material... just didn't think of it, however,

1) What method should be used to stuff the bubble sheet material into a banana shape tube...
2) How would a tube filled with air bubble sheets react when it is left in summer's sunshine or in cold weather... Would it expand or shrink deforming the outer shell...
3) Would it be sufficient impact resistant to withstand hard knocks at for instance "dingy docks"?

Thank you John for the measurements of the "Dingy Dog", tubes which is extremely useful and also their method of attaching the tube... much appreciated.

We're off to visit the kids for a bit so the project will be on hold until our return...

Edited by - on

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