Turning Bateau D5 Dinghy into a RIB.

[OneWayTraffic]

I have built my first project, a Bateau D5. Although happy with the outcome and performance of the boat relative to the size, materials and effort I put into her, I would like to drastically reduce her tendency to tip, while at the same time adding level flotation. The boat currently has a rear compartment with a hatch and enough pool noodles in both that and under the middle seat to float the boat alone.

Pictures and details of the build can be found here:
Stuart's D5 Dinghy. - Bateau2 - Builder Forums https://forums.bateau2.com/viewtopic.php?f=14&t=62403

At the moment I have been thinking over the following commercial options:

Airofloat stabilizers. At least $700 NZD including postage and fitting.

Kapten boat collars. I got a quote of $900 AUD including postage to NZ (posting foam isn't cheap.)

I also considered fenders etc on the outside but want a slighter better look.

I have thought about an outrigger, but would like an integrated option preferably.

The main DIY option I am currently looking at is to buy some polyurethane foam sheet, which I can locally buy in densities of 34,65 and 96 kg a m3, and then epoxy glue this in layers to the hull sides and glass over. I have a roll of 400g biaxial tape and would use West System 105. I could easily build up a good 20cm by 15cm by 2m for about 60 litres buoyancy a side. What I am not sure about is whether this last option would hold up to wear, tear and damage.

Of the above densities of foam, which would be the best option to use, and will a layer of 400g biaxial be sufficient to protect against bumps and impacts?

 

[Richard Woods]

My Duo dinghy was designed from the start to have an optional outer collar - why put buoyancy inside the boat where outside is more effective and takes up no space. On our Duo we started with inflatable beach rollers (very cheap,) but later we bought "dinghy dogs" which look neater but I think they are no longer made.

Later I saw Walker Bay sell a cheap(ish) inflatable tube for their 8 and 10ft plastic dinghies. That might be an option. Use webbing straps to hold them to the boat

Richard Woods of Woods Designs
www.sailingcatamarans.com

 

[OneWayTraffic]

Thank you Richard. I have seen photos of your dinghy with the tubes and thought it a neat solution. Sadly I do not see those tubes on the Walker bay website, and shipping to NZ would push up the cost considerably. I have seen a few places on the net with boat rollers, and am still considering that as an option though the shipping still pushes the cost right up.

I was wondering if you had any opinions on whether glassing over rigid polyurethane foam would have any impact resistance? This would be slow speed bumps and trailering damage only I hope! I could also stick some eva foam to the outside though that would look truly ghetto. This is a little trout and salmon dinghy, not a show piece.

I would do some tests on scrap panels first to be sure of course.

 

[Richard Woods]

I went here,

WB10 RID 310R Tube Kit https://walkerbay.com/shop/replacement-parts/rigid-dinghy/wb10-rid-310r-tube-kit/

but see they are out of stock. Maybe your local dealer has them? They do here in the UK

And boat rollers are typically like this

Osculati boatroll Slip Roller Towing up to 200KG Load Bearing Capacity Transport | eBay http://www.ebay.co.uk/itm/like/163071729800?clk_rvr_id=1565855493360&vectorid=229508&lgeo=1&item=163071729800&rmvSB=true

try searching for "pneumatic" as well as "inflatable"

400g is good, I'd use 65kg/m3 foam

RW

 

[David J Ritchie]

any opinions on whether glassing over rigid polyurethane foam would have any impact resistance?

all Fiberglass has good impact resistance but the core material is often the weak point. 2 main keys to success, 1 the core material has good impact resistance on its own, and 2 the strength of the bond between the core and epoxy.

I know the that PU foam (the rubbery kind) has amazing impact resistance so that answers question 1. As for question 2 i'm not sure about the bond strength you should check the epoxy data sheets.

 

[Squidly-Diddly]

Bateau D5 - Google Search https://www.google.com/search?q=Bateau+D5&source=lnms&tbm=isch&sa=X&ved=0ahUKEwje5IC8hdfbAhX_HzQIHatJBrcQ_AUICygC&biw=1760&bih=839#imgrc=HwzDePiHs5OWYM:

Looks like enough freeboard to install a double stack of 6" pool noodles on the sides and still have them clear the water with a single average size man.

Just add a few eyelets to the outside and run rope through the noodles, maybe with light gauge PVC inside the hollow noodles. I'm thinking eyelets on bow and stern panels, and amideships would be enough to keep the PVC re-enforced noodles inplace. The PVC would bend to make the noodles match the boat's lines. The amidships connection would be hidden under noodles.

That way you'd still have a "factory" design and it would only cost about $60.

 

[OneWayTraffic]

Picture of my boat included for clarity. I have a hatch on the rear seat. Mid seat and front compartment left open at present. The boat is powered by a 2.5hp outboard, has beachmaster dinghy wheels on the transom for launching, and weighs 40kg not including motor.


6 inch diameter pool noodles? It would be nice if I could find those here. The closest we have are the yoga rollers. Pool noodles here typically displace about 5 litres (about 3" diameter.) I have several of these under the mid seat and a few more in the rear compartment. The rear compartment is sealed with a hatch (probably not 100% water tight).

I looked into boat rollers, there are a couple of places selling in the USA, but the quality ones made from PVC coated fabric are almost $400 by the time I ship a pair here and pay GST tax.
There is a place selling half round yoga rollers for $20 each. I could glue these in place with contact adhesive along the sides. About 7 litres of buoyancy each so like most eva options that I see locally, not much better than nothing. Oh, and they are pink. I'd need 10 total for about half the buoyancy that I am aiming for.

Cheapest and lightest option that I see at the moment is strapping optimist buoyancy bags to the outside. I can buy them for $50 each for 50litres (about 110 pounds) and strap them to the outside. That would cost about $150 all up and only weigh a couple of kg. The bags are polyurethane coated nylon, and I am not sure how long they would last. They will also look kind of funny.

Fiberglassing rigid polyurethane foam to the outside would cost about $250 for the foam, epoxy, fillers, and paint but add 12kg in weight for 144 litres buoyancy.At the moment I am leaning towards this as an option. Weight is not that big an issue for my boat. I have beachmaster dinghy wheels to launch it and carry it on a trailer.

The walker bay tubes look nice but the cost is prohibitive. The Kapten collar would be my preferred option in that price range. (~$1000 NZD once imported.)

 

[Mr Efficiency]

The Kapten collars might have one to suit, but really I would look for a foam supplier that sells flexible polyethylene foam, they may even sell you some offcuts for cheap, and you can just glue it on with contact adhesive.

 

[Richard Woods]

quick google search found this PVC hauling roll 500 kg https://www.fishpond.co.nz/Sports_Outdoors/PVC-hauling-roll-500-kg/9999312649705

RW

 

[OneWayTraffic]

Thanks for that, I thought I was good at Google, but must have been using the wrong words.

I wonder how they would compare in longevity to the optibags?
Sail One | Optimist Boats & Fittings | Windesign Laser Parts | Far East Yachts | Product http://www.sailone.co.nz/Shop/product.aspx?p=504

The dinghy is primarily for fishing out of and I am sure that eventually fish hooks would find the sides which is a worry. I had an inflatable boat once before, the fabric was much stronger but still got leaks.

For both types of bags the trick is to securely lock them in place, block foam would be easier once installed but...

Foam seems to be hard to come by in my part of the country. NZ is a small country with expensive freighting both within and to the country.
This is the best deal on closed cell foam on a per volume basis:

Polytuf Interlocking Solid Black Foam Floor Mats - 4pk https://www.bunnings.co.nz/polytuf-interlocking-solid-black-foam-floor-mats-4pk_p00229789

If I were to buy eight and somehow manage to cut them to size and glue them perfectly they would do nicely as is without any extra I have my doubts as to how I am going to manage that, especially the gluing part. Contact adhesive would be ideal, but stacking that up several layers thick perfectly?

I have learned that surfboard blanks are usually 6-12 ounce cloth over polyurethane. They see much rougher service than my dinghy sides will, but also get dinged up and have a limited life expectancy. The advantage of this approach is that I get to build up as much strength as I need. I could even stick a layer of EVA on top.

 

[OneWayTraffic]

Found these, these are a reasonable cost.

Marine Warehouse FOAM FENDERS https://www.marine-warehouse.co.nz/foam-fenders

 

[Squidly-Diddly]

buoyancy each so like most eva options that I see locally, not much better than nothing. Oh, and they are pink. I'd need 10 total for about half the buoyancy that I am aiming for.

6 inch diameter pool noodles? It would be nice if I could find those here. The closest we have are the yoga rollers. Pool noodles here typically displace about 5 litres (about 3" diameter.) I have several of these under the mid seat and a few more in the rear compartment. The rear compartment is sealed with a hatch (probably not 100% water tight).


stack 4 3" dia noodles up the sides, then "honeycomb"out off that layer. I'm thinking 3 on 4, then 3 on 3, then another 3, then two.

I'd try pool noodles before any other mods just to get a feel of what the extra will feel like in real water.

 

[OneWayTraffic]

I will try that Squidly. I have some noodles at home so should be able to sort something.

Cheers.

 

[OneWayTraffic]

Found the following very neat website.

DIY Packraft – The homemade packraft how-to site & shop https://www.diypackraft.com/

I have ordered a sample pack of fabric for $10 including shipping.

The plan that I am toying with is to build two 2m by 0.25m diameter pontoons. 210D TPU coated fabric sealed with a heatgun. I can rig up webbing or something to hold them in place. If I go ahead I will post the results when done.

 

[Squidly-Diddly]

Found the following very neat website.

DIY Packraft – The homemade packraft how-to site & shop https://www.diypackraft.com/

I have ordered a sample pack of fabric for $10 including shipping.

The plan that I am toying with is to build two 2m by 0.25m diameter pontoons. 210D TPU coated fabric sealed with a heatgun. I can rig up webbing or something to hold them in place. If I go ahead I will post the results when done.

that looks worth ordering just because Inflatable Engineering seems to be such a black-art. I've asked and no one can give any pointers on how one might have at it.