Aluminum vs Fiberglass RIB

[djousset]

Despite my optimistic resuscitation efforts the old Mercury has finally given up the ghost.

In a new RIB, relative to the hull, I am looking at both aluminum and fiberglass. I understand there is a weight difference, and perhaps strength variances. Are there any other meaningful considerations in choosing one over the other?

[MicHughV]

Depends on how you plan to use it. If beaching it everyday, my vote is for alum.
If simply tying up to a dock, I'd go fiberglass.

[hlev00]

I love many things about my lightweight aluminum RIB. The two issues I have are 1) it is powder coated and that is starting to fail after 3 years and manufacturer won’t stand behind it. Better to avoid powder coating. And 2) it is so light that I am afraid it will flip when towing without the engine on it, and I never want to do any significant towing with the engine on. It flipped once when we were on anchor and a storm came through. It has weathered storms with the engine on. I sometimes think maybe towing with it half full of water might be worth a try.

[SailFastTri]

If you want to plane, Highfield has the best hull shape and will give the smoothest and driest ride in waves.
If you want to use a small-light motor, Highfield or AB will both provide a very dry ride (less splashing up over the tubes) with Highfield being drier.
People will say larger tube diameter will be drier, but that’s only part of the picture. A deeper V hull shape will displace more water than a shallower V, and the tubes will sit higher with the deeper V.
Fiberglass is easier to repair, and is not subject to electrolysis. It’s a better choice if you plan to paint it with antifouling and keep it in the water full time. If the coating on aluminum is scratched you will get electrolysis if the boat is allowed to sit in the water. If you want to paint aluminum with antifouling you will need an intact barrier coat of epoxy and the bottom paint must be specially made for aluminum (no copper).

[SailFastTri]

Originally Posted by hlev00

I love many things about my lightweight aluminum RIB. The two issues I have are 1) it is powder coated and that is starting to fail after 3 years and manufacturer won’t stand behind it. Better to avoid powder coating. And 2) it is so light that I am afraid it will flip when towing without the engine on it, and I never want to do any significant towing with the engine on. It flipped once when we were on anchor and a storm came through. It has weathered storms with the engine on. I sometimes think maybe towing with it half full of water might be worth a try.

You’ve now had enough experience to know towing or leaving on a mooring in open water is a recipe for problems. Leaving the engine attached while towing in open water is a mistake. Did you also leave the fuel tank in it, unsecured?
Partially swamping it is not the answer. Stop this and learn from your mistakes.
You either need a way to bring it aboard and stow it safely, or you need a lighter or larger tender (maybe one of each) appropriate for your intended use.

[JPA Cate]

Well, recommendations vary considerably, by location, and I don't know where is most convenient for djousset to order from...

But, our Gemini RIB aluminum hull is now 20 yrs. old. We both are very pleased with it. Good quality. It was stolen and set fire to, so the powder-coat was challenged; yet it is in excellent good condition condition. It is the same hull as Swift, here in Australia, but ours had Gemini tubes, South African lightweight hypalon tubes, applied here in Oz.

As the original tubes were destroyed in the fire, they were replaced with a 2nd set of Gemini tubes. Ten years ago, now, we replaced them with pvc tubes, which we covered w/in 2 weeks, first with Weathermax chaps; then replaced that 3 yrs ago with Sunbrella. The WM only lasted 5 yrs, it's guarantee period, and the Sunbrella should see us out.

We chose the alloy over grp because of lighter weight, which means easier to haul up steeper beaches (we use a round fender for a roller when doing this).

If you plan on a circumnavigation, imo, the alloy hull is a better deal for rocky beaches, but really, friends have a Caribe grp hull, and they have never complained about it, AND, theirs is smaller than ours, so overall weight is less of a problem. If it is an inflatable boat, the tubes are really vulnerable to oysters and other sharp things.

If you plan to cruise a long time, and go far--and have the shekels now, I'd buy alloy again, and with the heavier weight hypalon, planning for the long haul. We wanted a big dinghy for guests, and carrying SCUBA gear, but if guests are few and far between, for you, or you don't want to carry SCUBA gear, then a smaller dinghy will do quite well. It depends on if you'd like to be SCUBA qualified (not everyone does). If you buy small, then want bigger, you'll be crowded until you make the change, this isn't too bad.

Ann

[hlev00]

A RIB won’t plane as quickly as an inflatable and heavier fiberglass only makes it harder. If you want to be able to plane provide your estimated total weight (people and stuff) and ask for comparable experiences for boats that plane.

[Jammer]

Originally Posted by djousset

I am looking at both aluminum and fiberglass. I understand there is a weight difference, and perhaps strength variances. Are there any other meaningful considerations in choosing one over the other?

Aluminum is more abrasion resistant.


Fiberglass is easier to repair since bad areas can easily be cut out, patched with epoxy and cloth, and reinforced if desired. No special equipment, skills, or parts required, you can get epoxy and cloth anywhere.


That said, with skill and the proper equipment Aluminum can be welded, and minor damage can be fixed with sealant (5200 etc) until an opportunity for a permanent repair arises.


With care either will outlast the tubes. I have an aluminum boat made in 1960. I have a fiberglass boat made in the early 1970s. Both in good shape. (Not RIBs)

[boatpoker]

Originally Posted by SailFastTri

If the coating on aluminum is scratched you will get electrolysis if the boat is allowed to sit in the water. If you want to paint aluminum with antifouling you will need an intact barrier coat of epoxy and the bottom paint must be specially made for aluminum (no copper).

1. Electrolysis cannot occur on a boat of any kind. Electrolysis describes the decomposition of water (H2O) into oxygen (O2) and hydrogen gas (H2) due to an induced current being passed through an electrolyte using positive anodes and negative cathodes. You may be thinking of galvanic corrosion which is the exact opposite of "electrolysis" as the anode is negative and the cathode positive.

Still virtually impossible for an aluminum RIB to corrode unless one does something stupid like directly fastening a metal with a different voltage potential.

2. How do you explain the tens of thousands of unpainted, un-corroded aluminum hulls ? https://www.berthoninternational.com...83-wind-horse/

[Tin Tin]

We have had both glass and alloy, the glass ones need more HP. So for example a 3.1m alloy will be great with a 15HP to get same glass one would need a 20 which is a bit of a catch 22 as it is then heavier (and more expensive). Alloy is more difficult to fix properly especially stress cracks on transoms, frames and seams, this likely comes from towing water toys.

[JPA Cate]

Here's a link you may find interesting:

https://www.cruisersforum.com/forums...rs-256380.html

Good luck with the search.

[GordMay]

Originally Posted by JPA Cate

Well, recommendations vary considerably, by location, and I don't know where is most convenient for djousset to order from...

Diane lists her location as: New Hampshire, USA.

[Phyrcooler]

As others have noted, it is dependent upon your actual use. If you will be manipulating it solo much, whether it is dragging it up on a beach, or hoisting it aboard, lighter is always better. An aluminum single hull (no flat deck inside) is the lightest style you will find. A slight disadvantage is the floor is not flat, and depending on the V of the hull, is occasionally awkward moving around inside. Adding things like flat floor and bow locker add weight, but also add convenience - Features to assess for your use. For me, the trade-off was worth it, as my small 8.5’ aluminum rib only weighed about 70 pounds. It was nearly 20 years old and still held air well when I sold it. No corrosion to speak of in spite of the salt water/air environment.

[desodave]

I agree re the weight saving and durability of an aluminum RIB. We use it in an area with lots of rocky or coarse gravel beaches and the aluminum is way more durable ... as well as being lighter to drag up on those beaches. While we carry the dinghy on davits, we store it on the foredeck in our marina. There's some manhandling of it required when using the spinnaker halyard to load it, and any additional weight would be problematic for me. Ours is a single skin 10 foot Zodiac, often used for prawn fishing, so I wanted one with enough interior volume for 2 people, the prawn traps and enough stability to pull the traps by hand. The single skin aluminum was way lighter than an equivalent fiberglass unit.

[grantmc]

To me this is incredibly simple, just forget about the RIB component.

Solid hard dinghies are best whether aluminium or GRP wins hands down on virtually every aspect of a dinghy. Weight, durability, ability to be rowed, windage, and especially being beaten up by the Sun. You can abuse, misuse, pull them up rocky beaches, and hit rocks.
You want an extra thing like a lockable locker or handles, weld or glass in.
Want wheels, just bolt them on, easy peasy.
And the transom is completely solid for the engine.