Dingy conversion

dLj

dLj

.
Mar 23, 2017
3,895
Belliure 41 Back in the Chesapeake
Lot's of dingy threads, but here's a question I've not seen asked.

I met a guy who had gotten his inflatable hard bottom dingy changed to have the inflatable tubes converted to the some kind of hard replacement. It worked great as a dive platform as well as never having a problem with deflating. I asked him how it was done and he said he didn't know, it was done down in Central America by some guy and he used some kind of product to replace - or possibly cover - the inflatable tubes making them hard. I believe then filled with foam, but I'm not sure of that.

I own an old Carib and it is getting long in the tooth. I'm thinking I may like to have this done to it. I know this is kind of a vague question, but just testing the waters to see if anyone might know how this can be done. That dingy was pretty much indestructible!

dj
 
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D

dlochner

.
Jan 11, 2014
12,351
Sabre 362 113 Fair Haven, NY
dLj said:
Might be that simple - then fill with closed cell foam... It was a very cool dingy...

dj
Click to expand
An expanding foam would fill the tubes. Leave the fabric on the outside of the tubes alone, no need to replace, just patch any holes.
 
dLj

dLj

.
Mar 23, 2017
3,895
Belliure 41 Back in the Chesapeake
dLj said:
Might be that simple - then fill with closed cell foam... It was a very cool dingy...

dj
Click to expand
I'm trying to imagine how to do that and not have "holes" in the foam....

Then the problem of having all the attachments - oar locks, towing ring - all attached. Still have the problem of all those degrading in their connections to the Hypalon tubes

dj
 
D

dlochner

.
Jan 11, 2014
12,351
Sabre 362 113 Fair Haven, NY
There is probably a bit of technique born of experience involved.

Off the top of my head I can think of two ways.

Open one end of the tube and inflate it a shop vac on exhaust, then mix and quickly poor the foam into the tube and let it expand into the tube. It would have to be done vertically.

Or, using foam in a can like builders use, poke a series of holes in the tube, insert the straw into the hole and fill that section of tube, move onto the next section.
 
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Head Sail

Head Sail

.
Nov 13, 2013
723
Catalina 34 Tacoma
dLj said:
Might be that simple - then fill with closed cell foam... It was a very cool dingy...

dj
Click to expand
Once the tubes are glassed over, deflate the tubes. Drill several holes in the glass to fill with foam. Or, don't deflate and drill and fill.
 
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garymalmgren

garymalmgren

.
May 29, 2018
505
Canel 25 foot Shiogama, japan
I am sorry fellas, BUT...
I can't see pouring expanding foam into the tubes working.
Coconut fibers stuffed in tightly?
Also I can't see a glassed over floor taking basic wear and tear let alone having air tanks dropped on them. Splinters in your feet? No thank you.
Plywood floor?
I am intrigued to know how it was done though.
 
dLj

dLj

.
Mar 23, 2017
3,895
Belliure 41 Back in the Chesapeake
garymalmgren said:
I am sorry fellas, BUT...
I can't see pouring expanding foam into the tubes working.
Coconut fibers stuffed in tightly?
Click to expand
You need a way to not allow water to accumulate inside the tubes - hence the closed cell foam - Closed cell foam is used for flotation and does not absorb water. Coconut fibers would become a problem over time I'd think.

garymalmgren said:
Also I can't see a glassed over floor taking basic wear and tear let alone having air tanks dropped on them. Splinters in your feet? No thank you.
Plywood floor?
Click to expand
I was not too clear above - the hard bottom dingy has a fiberglass hull. The question has nothing to do with changing the hull. Only how to treat the flotation tubes.

garymalmgren said:
I am intrigued to know how it was done though.
Click to expand
I wish the guy I met who had the dingy knew more. He claimed he just had it done for him by some artisan - he didn't even remember who that was or I'd see if I could get that person to do it. Sadly, I have very little information other than I rode in his dingy, and it was quite a nice dingy...

dj
 
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PaulK

PaulK

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Dec 1, 2009
1,321
Sabre 402 Southport, CT
There was a video about putting inflatable cargo bags (used to hold cargo in place on trucks) inside damaged RIB's to make them last longer. Sort of like an inner tube on a bicycle tire. Instead of 'glassing the outsides and filling the tubes with foam, wouldn't it be easier to simply purchase solid foam blocks, cut them to shape and 'glass over that?
 
rgranger

rgranger

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Jan 19, 2010
12,548
Hobie 16 & Rhodes 22 Skeeter Charleston
Head Sail said:
Interesting idea. Maybe inflate then glass the tubes?
Click to expand
That was my first thought also. I think it would be interesting to go to one of those custom auto shops that do all sorts of fancy fiberglass work and ask them if they thought they could glass over your tubes.... and put a nice gel coat on them... and finish with a custom airbrush paint job, gloss and buff. You could then finish with a few strategic access ports so you can install backing plates for your hardware (i.e. D-rings, cleats etc.)
 
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J

JBP-PA

.
Apr 29, 2022
512
Jeanneau Tonic 23 Erie, PA
Pourable flotation foam is actually quite easy to work with, much easier than epoxy. Just quickly mix and pour, then watch it poof! Not the canned stuff which is messy and rarely does a good job. While the pourable foam expands a great deal, it does not have much force (unlike the canned stuff), so you need some way to keep the tubes open while it cures (which only takes a few minutes). Thus inflating and glassing the tube first. You could also use any other method to stiffen the tubes.
 
jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,303
CAL 35 Cruiser #21 moored EVERETT WA
With all these ideas, does anyone have an idea how much weight will be added in the process to the dinghy? Is it an issue?

I would think the choice of a dinghy might be best approached by deciding how it is thought to be used.
  1. Is this just a 100 yard taxi to get from anchorage to shore and back?
  2. Is it a tool to explore several miles from the boat?
  3. Do you need power to plane the boat, traveling at speed or a boat that glides smoothly under oar power?
  4. Should you be looking for a light weight dinghy or one that can nest/fold up when on board during a passage?
  5. Should the dinghy home be on the bow or hanging from davits on the stern (what would happen in breaking ocean swells?)
More questions than answers.
 
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jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,303
CAL 35 Cruiser #21 moored EVERETT WA
What are the cubic feet of an inflatable dinghy air tubes?

What are they 8" or 15" diameter tubes?
 
dLj

dLj

.
Mar 23, 2017
3,895
Belliure 41 Back in the Chesapeake
jssailem said:
With all these ideas, does anyone have an idea how much weight will be added in the process to the dinghy? Is it an issue?

I would think the choice of a dinghy might be best approached by deciding how it is thought to be used.
  1. Is this just a 100 yard taxi to get from anchorage to shore and back?
  2. Is it a tool to explore several miles from the boat?
  3. Do you need power to plane the boat, traveling at speed or a boat that glides smoothly under oar power?
  4. Should you be looking for a light weight dinghy or one that can nest/fold up when on board during a passage?
  5. Should the dinghy home be on the bow or hanging from davits on the stern (what would happen in breaking ocean swells?)
More questions than answers.
Click to expand
John, you should know my use. The dingy is a water taxi. To be used extensively in any port of call. To shlep supplies, to run around to places where the mother ship can't go.

Now the questions as to carrying when on passage, I personally never carry on davits. It's either on the foredeck of stored inside if you have a foldable.

dj
 
DArcy

DArcy

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Feb 11, 2017
1,754
Islander Freeport 36 Ottawa
I know someone who tried expanding foam in an old inflatable. Short story, it did not work. I only saw it after, not during the attempt to fill the tubes. My understanding was it was too hard to keep the tubes in the "full" shape while pouring foam in. You can't maintain pressure while pouring and without pressure the tubes just flop around. There were voids in the foam all over the place and it was heavier than a boat with inflated tubes. He ended up with a heavy piece of garbage that he had to dispose of.

I like the idea of removing the old tubes, shaping some low density foam to the tube shape and then glassing over it. A lot of work but if done properly you could end up with a decent boat. You could make templates based on the current tube shape before cutting them off. It would be worth figuring out the weight difference ahead of time. I know the rib in my profile photo planes very well with a 9.9hp and 2 people but not with 3 people. It is a double floor aluminum hull so maybe a bit heavier than single floor glass boat. Weight can be an issue if you want it to get up and go.
 
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dLj

dLj

.
Mar 23, 2017
3,895
Belliure 41 Back in the Chesapeake
dlochner said:
When considering these kinds of projects, one must wonder what one's time is worth. Could be a case of penny wise and pound foolish. ;)
Click to expand
That's where my mind is heading....

dj
 
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