Fiberglass or aluminum?

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BoyoBoyle

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https://erie.craigslist.org/boa/1392698808.html

Ok Im looking to mod a jon boat and I really want a 14 ' one. I found this one but it's fiberglass. Is this good? I know im gonna be screwing holes into it for mods, so is fiberglass a good pick for this? Basically i'm asking.... if you're going to mod a jon boat.... what would you prefer, aluminum or fiberglass? Its a good deal for a boat and trailer.
 
BoyoBoyle said:
Ok Im looking to mod a jon boat and I really want a 14 ' one. I found this one but it's fiberglass. Is this good? I know im gonna be screwing holes into it for mods, so is fiberglass a good pick for this? Basically i'm asking.... if you're going to mod a jon boat.... what would you prefer, aluminum or fiberglass? Its a good deal for a boat and trailer.

Fiberglass is fine, and your not going to need to put holes in the hull unless you need to add drains or water pick ups (live-wells etc). In a fiberglass hull all the framing can be glued to the inside of the hull using epoxy glue (like Gel-Matic, or you can make it) and will be stronger than using a fastener like screws or bolts. Epoxy resin and fiberglass aren't cheap, but it's forever. However you can also glue the framing and then add weatherproof treated lumber (not pressure treated, too heavy) to finish the decks if you plan on using carpet. Epoxy resins and fiberglass aren't that difficult to learn to work with, but are generally more expensive than using fasteners, and take longer. Ultimately tho it will last longer and proly be lighter. The first 1648 ply/composite hull I helped build weighed 231 pounds with all the hardware, a comparative riveted hull Lowe weighs over 400 pounds. I could achieve the same speeds with half the HP.

If it's a good deal I say grab it up and make it what you want. Epoxy and Fiberglass can be learned pretty easy...

Can you post some pictures of the hull you are looking at?
 
The only pictures I have are in that link.

So Im not even gonna use any bolts? I just glue my floor units onto the boat? will this be sturdy enough? Im really new to this but am ready to get started. I just need some advice.

Do you think it would be a good idea to mod a fiberglass boat? Do many people do it? What are the advantages and disadvantages? See.... i dont even know if it really is fiberglass. it might be aluminum and the owner might be mistaken.
 
I my opinion, an open glass hull is easier to work with than aluminum and Rat hit it on the head why: When modifying fiberglass hulls, you can use epoxy resin instead of mechanical fasteners.
You use marine plywood & epoxy for all bulkheads, knees, storage boxes and decks. No need for complicated aluminum framework, rivets, screws, etc.. The wood soaks the expoxy into its grain and the expoxy bonds with it & the glass hull. The joint ends up being stronger that the materials it holds. Scarf 2 pieces of wood and glue them together with expoxy. then see if you can break the joint, the wood will always break before the joint does.
Heck, if you coat it with expoxy resin & glass, you can even use marine plywood to build livewells.

Make sure to remover all paint, dirt and oil to make sure you get a good bond between the wood, epoxy and hull. And use strategically placed bulkheads and knees to insure the structural stability of the hull & eliminate flexing.
 
BoyoBoyle said:
The only pictures I have are in that link.

So Im not even gonna use any bolts? I just glue my floor units onto the boat? will this be sturdy enough? Im really new to this but am ready to get started. I just need some advice.

Do you think it would be a good idea to mod a fiberglass boat? Do many people do it? What are the advantages and disadvantages? See.... i dont even know if it really is fiberglass. it might be aluminum and the owner might be mistaken.

Read through my build here:
Rat's 1440 Refit

In the images you can see how I installed cleats along the sheer line/gunnels and a single rear frame (on the back of the front seat) to support the fore deck, there is only a small stiffener running centerline for to aft of the deck for support and it is as stable as anything, without a bunch of framing required. Same thing on the aft deck, cleats all the way around and a frame on the front of the rear seat, no framing at all.

Working with epoxy and glass takes more time, is more expensive and there is a learning curve; but it's no more difficult than traditional decking, weighs less, results in a stiffer boat, and will outlast other types of finishes 2 to 1.

Lots of people rebuild and modify fiberglass boats. I have helped rebuild 2 fiberglass hulls from the stringers up and modified decks/caps on a few others.

Here's a pretty extensive rebuild video in pictures on youtube:
[youtube]<object width="425" height="344"><param name="movie" value="https://www.youtube.com/v/ksHkfRJSORA&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="https://www.youtube.com/v/ksHkfRJSORA&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>[/youtube]
 
Thanks for the tips so far guys. So is the glass boat gonna be heavier or lighter than an aluminum boat? How will it float compared to the aluminum boats?
 
Weight depends on alot of factors, cant really say. Normaly, size for size, a glass boat is heavier. But that depends. Take a lightweight AL boat and put bunch of framework, decks & stuff init and it can get heavy quick.
How much will it draft? Once again, lots of factors, such as hull design, weight etc.. In most cases, draft will be same or close to an AL hull of the same shape, length & width.

Working with a glass hull is similar to stitch & glue hulls once the hull is built. Check out https://www.devlinboat.com/ and some of the boat builds on duckboats.net.
 
BoyoBoyle said:
Thanks for the tips so far guys. So is the glass boat gonna be heavier or lighter than an aluminum boat? How will it float compared to the aluminum boats?
The boat in the picture is definitely fiberglass.

The glass boat will be heavier. Boats of that era are going to have wood cores. The glass will entrap little bits of water inside, and rot the boat from the inside out. Sun also wreaks havoc on fiberglass. I can't for the life of me figure out why anyone would build a BOAT out of a material that is susceptible to WATER damage.

On a glass boat, you would be building whatever decking you would need, then using fiberglass mat, and either polyester or epoxy resin to coat it. It would be attached to the boat using more mat and resin.

I am going to have to call BS on the statement of fiberglass work being easier. You will likely find the workload to be higher, and a bigger pain in the neck (and lower back, if your back is like mine), to do the glasswork. Instead of screwing/riveting materials, you'll be using mat and epoxy resin to overlap joints. However, once you start grinding and sanding old fiberglass, you will wish you had gone aluminum.

The aluminum hull is going to be a much simpler hull to work with, and will give you a better/stronger hull to start with, that will also have increased resale value. And, if worst comes to worst, there is always a scrap value for a wrecked aluminum hull. You have to pay about the equivalent per pound to dispose of a wrecked glass boat.
 
bassboy1 said:
BoyoBoyle said:
Thanks for the tips so far guys. So is the glass boat gonna be heavier or lighter than an aluminum boat? How will it float compared to the aluminum boats?
The boat in the picture is definitely fiberglass.

The glass boat will be heavier. Boats of that era are going to have wood cores. The glass will entrap little bits of water inside, and rot the boat from the inside out. Sun also wreaks havoc on fiberglass. I can't for the life of me figure out why anyone would build a BOAT out of a material that is susceptible to WATER damage.

On a glass boat, you would be building whatever decking you would need, then using fiberglass mat, and either polyester or epoxy resin to coat it. It would be attached to the boat using more mat and resin.

I am going to have to call BS on the statement of fiberglass work being easier. You will likely find the workload to be higher, and a bigger pain in the neck (and lower back, if your back is like mine), to do the glasswork. Instead of screwing/riveting materials, you'll be using mat and epoxy resin to overlap joints. However, once you start grinding and sanding old fiberglass, you will wish you had gone aluminum.

The aluminum hull is going to be a much simpler hull to work with, and will give you a better/stronger hull to start with, that will also have increased resale value. And, if worst comes to worst, there is always a scrap value for a wrecked aluminum hull. You have to pay about the equivalent per pound to dispose of a wrecked glass boat.

Obviously you have never built or worked on fiberglass hulls.
Glass is NOT heavier! Where do you get this? Check these hull weights for yourself:
Lowe 1448
Prostrike 1455
Same size hull, the Alum is 100 pounds heavier. These are both production boats.
The 1648 I helped build was over 200 pounds lighter than a production Alum hull of the same size; and it was a wood core boat.

Glass will not entrap little bits of water inside and cause wood rot. If this happens it's because the glass wasn't laid down correctly in the first place. That's like saying a welded hull will leak, it will if you don't know how to weld! Most production hulls use Poly or vinyl ester resins which allow water intrusion, poly is water permeable, Epoxy is not. Wood protected with Epoxy resin will never have water touch it, and it will NEVER rot. Production boats also have sloppy holes drilled in them in several places. The Skeeter I rebuilt had holes drilled through the stringers for chokers to fit through when they moved the hull with a lift. They were not protected and water rotted the stringers. Don't drill holes through your epoxy/glass coating and you will not have this problem, seal or pot all screw holes to eliminate water intrusion.

You say that cutting, screwing, riveting and welding Alum are easier. I don't think they are, not for me anyway, and I know how to do it. I would rather build out of epoxy and glass. But saying one form is substandard to another isn't giving the other form it's just dues either, it's just a builders preference.

The sun does not hurt epoxy if it is painted with a topside paint, you are thinking of gelcoat, not the same thing, not even close.

Sanding and grinding old fiberglass does suck tho, I agree there.

If you wreck your Alum. hull you hafta take it to the scrap yard; if I wreck my glass hull I can repair it! :mrgreen:

Basically there are advantages and disadvantages to every building method and material. I prefer epoxy/glass, some prefer Alum and yet others prefer rotomolded HDPE. I was trying to give you the advantages and disadvantages to both (not just slam one material), which is what you asked for in your original post.

Sorry for the rant...
 
Bassboy, your advice is normally right on, but in this case you are way off mark, IMO.

There are fiberglass coated cedar strip boats out there that are 50-60 years old with no water infiltration. Plus the current stitch & glue technology makes a fantastically strong water proof boat. Properly constructed, using epoxy resin, glass matt and marine plywood, a stitch & glue hull is just as good as any tin boat out there in every aspect.
Sure if you screw up the glass it will leak, but so will an AL boat if you screw up the welds or rivets.

Dont use polyester! It is an inferior product compared to epoxy resin and has very few if any proper applications in the marine environment. Polyester resin is terrible about delaminating from wood and creating the type of water infiltration problems that give wood boats a bad name. I am betting most wood/glass boats with water infiltratoin problems were improperly constructed using polyester resin. Epoxy resin is the only way to go.
 
Obviously you have never built or worked on fiberglass hulls.
Never built one, no. But have done plenty of work on them - enough to know how much better aluminum hulls are IMO.

Glass is NOT heavier! Where do you get this? Check these hull weights for yourself:
Lowe 1448
Prostrike 1455
Same size hull, the Alum is 100 pounds heavier. These are both production boats.
The 1648 I helped build was over 200 pounds lighter than a production Alum hull of the same size; and it was a wood core boat.
While I can't say for sure the answer, I would wager a good sum that the aluminum hull will take a little better pounding before sustaining major damages. Built two identical size boats, and match the strength of certain aspects, and see which one is lighter then. I am basing this presumption on my dealings with both aluminum/fiberglass boats and custom performance auto body pieces.

Glass will not entrap little bits of water inside and cause wood rot. If this happens it's because the glass wasn't laid down correctly in the first place.
You did catch me on a generalization here, when I should have mentioned the pictured hull. I didn't mean the new glass he laid down, but the existing boat. While I said it will, I should have stated that statistically, production boats tend to have minor flaws that allow water in, and production boats of that era used polyester resin. Thus, transom and deck problems, caused by water, tend to be much more prevalent in glass boats, and generally require more time and effort to replace.

Once the gel coat fades off, the older fiberglass is known to blossom. Nothing was said about his new glass, but the older stuff likes to blossom up when exposed to heat and sunlight.

You say that cutting, screwing, riveting and welding Alum are easier.
Before posting the first post, I edited the rest of the paragraph to not say easier, as I knew someone would call me on that. Missed that sentence. What I put in the rest of the paragraph (and meant to put there) was that the workload was going to differ, which it is. Nobody on this board can say which is easier, and it fit all, as we all have our strong points and weak points, but we can agree on which physically involves less work.


Dont use polyester! It is an inferior product compared to epoxy resin and has very few if any proper applications in the marine environment. Polyester resin is terrible about delaminating from wood and creating the type of water infiltration problems that give wood boats a bad name. I am betting most wood/glass boats with water infiltratoin problems were improperly constructed using polyester resin. Epoxy resin is the only way to go.
Leads right back to something I posted earlier about the boat being built of polyester resin. It was most common in the '60s and '70s when that was built, right at the start of the fiberglass boat heyday.

If you wreck your Alum. hull you hafta take it to the scrap yard; if I wreck my glass hull I can repair it!
Me to. With the tools you have in your garage, that you use on your glass rigs, very likely. You might be surprised at how much can be done with aluminum, with how few specialized tools.
 
Okay, I am building a 16 foot by 48 inch (at the chine) modified Garvey jon boat. It is a Jacques Marten design, 100% wood core composite fiberglass construction, stitch and glue.

You build an Alum hull to the same specs.

The program: Keep it as light as possible while still being structurally sound, using industry specs for safety margins of the material being used. 15.5-16 feet long, 48" at the transom, 20" shaft transom.

We will weigh them
power them
race them
and then we will play chicken with a few levees I know about.

See which one breaks in half first. :mrgreen:

I guarantee mine will be lighter, need less power to go as fast (or faster) and take as much abuse as any Alum boat built, by anyone.

I know it will never happen, but it would be cool to do!

I don't have any special tools for glass except for a $6 lamination roller for corner fillets. I wouldn't be surprised about how easy Alum is to work with. I have built and worked on both types of hulls, as well as HDPE and cardboard (engineering project). So I am familiar with Alum hulls. And other than a MIG or TIG there aren't many specialized tools.

Anyway, my point is that there are many different hull types due to the many different needs/wants/budgets of boaters. One hull type and/or material doesn't fit all programs, but they do crossover. And there are Pros and Cons for each type of hull and material.

My opinion is that Jon boats are better suited for stitch and glue wood core composite construction then they are for traditional ribbed Alum hulls. The specs don't lie, they are lighter, require less HP, are faster and take the abuse as well as any material or better.

I know of a 16 foot 48 inch flat bottom that runs 43 MPH with a 25 HP motor (no mods). The boat is stitch and glue, wood core composite. Do you know of a 1648 Alum that can do 43 MPH with a 25? Wildman has a 35 on his 16 footer and it only does 32 MPH.

But I'm not knockin' Alum hulls, I own two of them! And for the vast majority of people they are great and will work fine. But they aren't for me the best option.

I also make my own Diesel fuel, sleep in a hammock and run a Linux OS! :mrgreen:
 
I reallly like my current boat,probably keep it forever 1652 aluminum,fits the lakes I fish.That being said,there are a few things I'd like to change(add) and I'm kinda slacking because I want it to look good and I'm not sure I can do the job properly by myself.
I built a 14' fiberglass boat before this one(15years or so),4 peices of paneling,10 gallons resin,some woven roven and mat,$600/.Never worked with fiberglass before but went pretty good,little messy and sticky but never had a problem with adding or changing things around.The boats still going,gave it to a 20 year old next door,he put new gunnels on it and still uses it for ducking.
So for me it would be easier to modify with fiberglass,know corrosion or welding issues.C34427.jpg
I think if I could weld,I'd be modifing the aluminum alittle.,love the boat though.
 
Rat said:
I know it will never happen, but it would be cool to do!
You dang right it would be. I'd take you up on that if I had the funding laying around. Hey, if someone with a spare couple hundred thousand wants to spend it in the name of science, we tinboaters would put this discussion to bed for good. Test out 6 or so different hull designs under a variety of tests...... :D :D

How 'bout this. I am going to start a 20 foot + 2 foot motor pod aluminum hull - 15 - 16 degree deadrise (have yet to redraw plan), 3/16 bottom, 1/8 inch sides. Powered by a 175 or so. Match that, and its on. I KNOW the answer to that one. :lol:


My opinion is that Jon boats are better suited for stitch and glue wood core composite construction then they are for traditional ribbed Alum hulls. The specs don't lie, they are lighter, require less HP, are faster and take the abuse as well as any material or better.
Okay. You got me on the strength and weight, and all those other numerical figures, on your new, and for the most part, non production hulls. But, I can still argue how aluminum is better for most modders and such, and quote your posts the whole way through. :wink:


However, lets take a look at the intended hull of the original poster, or just about any production boat from that era. Tell me that boat will be lighter than the equivalent aluminum hull, or will be more structurally sound, or won't be made with polyester resin. Again, I got hung up on generalizations (seems to be a trend for me, now doesn't it), so while my statements hold no water against these new technology glass jons, they sure hold up against these older hulls, which get much more attention by those interested in modding, than the new stuff. I think we can both agree on that. :wink:
 
A 22 footer powered y a 175 w/ 15° deadrise (@ the transom I am assuming). What style hull? Panga, Garvey, Skiff? Maybe an Abaco? I've so wanted to build an offshore sportfishing boat!

It may take three years or so, but it would give me a good excuse to build another boat! I don't think I could build a 20 footer that would handle a 175 HP, they are just too light and the USCG formula will not allow it. I could build a 23 footer to handle it tho, the Abaco again.

Old glass hulls aren't that bad to rebuild, even if you gotta refit all the wood in them. It's proly more work than most people are willing to do tho. Heck, adding a deck to an Alum is more work than most are willing to do. but I don't think Alum is better for most people, just what they are most familiar with and maybe easier because of that, but, resin/glass is easy to learn.

But you may be right, the hull in the original post may not be worth rebuilding, I haven't seen it. But unless there are big gaping holes in the side panels or floor I would consider it, and so should the original poster if it's a good enough deal.

I'm going to go study the Abaco 23 Plans some more...
 

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