'Disruptive Technology' RBB Discussion

[mikefrancis]

For lovers, supporters and detractors of RBBs - an interesting discussion is going on here:

Bateau2 - Builder Forums • View topic - A new boat concept EXCLUSIVE to readers of this Forum

Contributions (good/bad/indifferent) welcome!

Mike Francis
Armadillo Designs
Naples, FL.

[Poly]

Mike,

As the owner of a RBB with HDPE "tubes" perhaps I have some insight...

Disruptive technology
I know its 'trendy' to describe stuff as disruptive, but IMHO its only disruptive if it essentially displaces the existing approach - and changes the business for ever. GRP was disruptive. In sailing dinghies rotomolding was disruptive. But this, whilst possibly having a niche application is unlikely to be a revolution in boat building that "everyone" ends up following - is it?

Rigid tubes
I've got "rigid tubes" so I full recognise some of the advantages - not least when people post on here about leaking seams or punctures etc. But there are some potential disadvantages. The first is that tubes are nice and squishy so act like a giant fender all round. Whilst HDPE is pretty robust so you have to try hard to damage your own boat, for coming alongside delicate fibreglass boats etc an inflatable tube definitely has an advantage especially in choppy conditions or with inexperienced helms. For your intended workboat type application that may be a big issue.

Its also been suggested to me that inflatable tubes act as a shock absorber bouncing over the waves. If that effect is real rigid tubes must be less comfortable. I'm not sure how big this effect is with most ribs driven in most conditions - often the tube is well clear of the water the majority of the time so can have no effect then. But in seriously tough conditions it might be important.

Design
One of the downsides of inflatable tubes is they encroach into the useable beam of the boat. Its a shame that solid tubes aren't able to utilise this space effectively for storage or seating. At least with squishy tubes they make OK seats for short distances. I'm not sure how beamy the hull design is anyway - but it looks like the V may be less serious than on many "workboat / commercial" style ribs.

Foam filled
I'm surprised this is necessary. What advantage does it bring? Are you expecting leaks?

Corrugated
The other forum explains why, and also how you overcome the issue of the rough surface adding drag - but generally smallish ribs want their tubes touching the water at rest for the added stability. I'd be investigating ways of shaping uncorrugated pipe if this was the route I was following.

Why a complete boat?
Now in the US where tube makers are few and far between, and costs eye wateringly high as a result, there *MIGHT* be a market for "aftermarket" tube replacements, or even as an option for builders to incorporate into new builds without that expense. In the UK there are several tube builders which keeps costs down, but even here I guess if you could really retube a 6m boat, DIY, for <<£1000 it would get some interest from refurb projects - but you aren't going to sell enough to make a living from it, and as with any new tech you will need to wait till there is a critical mass of users that it seems normal to get any real traction.

Bow and Stern pieces
Probably the hardest part to get right with inflatable tubes too - but it looks like custom mouldings or aluminium pieces are planned? Surely that is expensive and complex.

The Hull material
All the benefits of uber-robust HDPE tubes are lost as soon as you put them on a fibreglass boat. You've just moved the most vulnerable bit of the boat to being the most expensive and hard to replace! Workboats are often kept afloat - but will need antifouling - HDPE is actually very good for not fouling so I'd be asking why not make the whole boat from the same material - which then leads to why not use one of the rotomolded boats - which aren't constrained in tube design to whats possible with low cost piping.

Overall
What problem is it you are trying to solve? and have your design compromises introduced other disadvantages which outweigh the benefits you might have brought from cheaper tubes? Tubes probably make up < 20% of the overall cost of a ready to use RIB/trailer/engine/electronics package anyway.

[willk]

HDPE collar on UK built RBBs: Flugga Boats home page

[mikefrancis]

Originally Posted by willk

HDPE collar on UK built RBBs: Flugga Boats home page

Yep, absolutely. And like the SAFE range of boats mentioned in the first post on the Bateau forum on this topic, Flugga Boats are designed and built commercially. That means significant investments in production tooling. HDPE smooth wall tubing requires such tooling to be able to conform to the compound shape of the hull.

The Bateau forum is aimed at the home constructiion builder.

Armadillo is similarly aimed at home construction. No production tooling, the corrugated pipe easily conforms to compound curvature, and even the bow and stern end caps (which by the way, are all identical) are mass produced HDPE drainage system items, available off the shelf.

Filling the corrugated wall tube with foam 1) locks the final shape 2) provides additional security and safety in the event of failure of the outer tube, and 3) adds a degree of 'firmness' to the tube.

In common with every boat ever designed, Armadillo has many compromises, not least because of the target market its aimed at. Buikding and testing the prototype will see how close we got to meeting design specification.

Mike Francis
Armadillo Designs
Naples, FL.

[Poly]

Originally Posted by mikefrancis

Armadillo is similarly aimed at home construction.

But its designed (and described in the other forum) as a workboat... ...do you think many workboat users build their own?

[mikefrancis]

Originally Posted by Poly

But its designed (and described in the other forum) as a workboat... ...do you think many workboat users build their own?

A workboat is listed as one application, but sure they do - go to the plans and kits link at the top of the Bateau forum intro page:

Bateau.com - boat plans online since 1993

Jacque Mertens latest design - the GP21 - is one example of multiple applications of the same basic design. There are several more examples.

Mike Francis
Armadillo Designs
naples, FL.

[capntroy]

I designed and built a RIB pilot boat for use by the Long Beach (California) Pilots, this has proven to be a very reliable boat for this service. It was recently re-tubed after 7 years of hard use which included multiple patchings after contact with the sharp edges of gangways, barges, etc.



The pilot boat application might lend itself to an HDPE or similar tube, although it would need to be mated to some type of shock absorbing material or device positioned between the tube and the hull...the hard ship landings would be too violent on the passengers as we learned the hard way with the company's larger pilot boat that had a rubrail made from poly pipe.



Aircraft tires finally had to be installed outside the poly pipe to mitigate the shock of moderate to hard landings.

I think that the idea of HDPE tubes would work out great for workskiffs that routinely come up against oil platforms, barges or other known tube-killers, but would definitely not be my first choice for a RIB that was used in the SAR/rescue world and needed to work against sailboats, runabouts or yachts or needed to pluck folks from the water.