Best hull manufacturing method

We're looking at making our own purpose-built FRP hulls for our tailboat product (www.tailboats.com). We're looking at methods appropriate for production quantities...but like everyone, have a limited budget to work with and are watching the pennies. (g)

The hull form would be that of a sit-on-top kayak with self-bailing drain holes between cockpit and bottom...or an open transom design similar to, say, the Virus Yole model (www.virusuk.demon.co.uk/yole/index.html). The hull will nominally be 16' WL x 32" beam...max displacement circa 500 lbm. Ideally, I'd like to get the bare hull weight down to below 60 lbm.

I've been researching the various manufacturing methods, and the optimum solution is by no means clear. I've recently come across information of the vacuum-assisted resin infusion and believe it may be a good candidate. I'd like to use a closed-mold approach whereby the deck and hull can be molded as one piece..say, similar to the technique being used by Rocat (www.rocat.co.uk/news/archive.htm)

We would also like to mold in a trunk through which we can insert a removeable daggerboard.

We'd also like to mold in wood hardpoints to which propulsion system components can be fastened to.

I'd be grateful for any guidance as to the best manufacturing method. We are open to all methods including rotomolding and blowmolding.

Any information on the respective tooling costs, estimated hull manufacturing cost, etc would also be extremely helpful.

Thank you for your help.

Best regards,

Tom McGuinness
Pacific Tailboats

 

tom,,I don't have much to add ,,,except to say that once the infusion process is mastered,,the obvious benefits seem immense!----I'm interested to learn more about the 1 peice hull-molding system that is featured in the 'rowcat' link in your note--do you know of any further 'links' to learn more of this process?...
(I realise that I'm somewhat de-railing this thread,so have posted this question as a new thread entitled "1 part boat-no glued flanges")...thanks.

 

Resin infusion is some tricky work. I have not personally done it but from what I've read, there's a significant learning curve. Seems that perfecting vacuum bagging is the first step toward perfecting infusion. So maybe try your hand at that first.

One alternative is a 2-piece fiberglass hull. I have a project with a client where he's building a mold plug from wood on a cnc-cut heavy framing system. He's taking the plug to his hull manufacturer and having the mold made from it.

The 2 pieces have an overlapping lip which serves as the attaching seam.

I'm guessing you're looking to make your hulls in-house so you'll have to learn about working with fiberglass in general.

 

The process/tooling used by Rocat looks very interesting. I'm still very much in the learning process. You may want to consider contacting Rojac, a marine tooling company in the UK. Their URL is "www.rojac.com". There appears to be a number of vacuum infusion processes around, several of them are patented such as the SCRIMP process owned by TPI.

There's also a fellow who gives hand-on training courses in the vacuum infusion process ("VIP"). Their URL is "www.grpguru.com". I'm considering going to their December course in Reno.

Hope the above is helpful.

 

Hi
Am interested to to see that my one-piece hull-moulding technique is already being talked about ... the wonders of the internet. But I'm also curious as to why, if you are interested in the process, you post a question here, rather than ask me straight.
I thought long and hard about whether, or not, to patent it. In the end I decided not, but to publish a description of it instead. So far as I know (and I've searched pretty hard) we are the only people making composite hulls like this in one piece.
Jem says "Resin infusion is some tricky work. I have not personally done it but from what I've read, there's a significant learning curve." ... that depends where you are coming from. As far as I'm concerned, vacuum resin infusion is the only way forward in composites. I don't have a composites background at all, which is perhaps why I had no problems doing it! But it really is very easy, you get amazingly consistant parts and SO much less messy than wet layup.
If you have specific questions, I'll do what I can to answer them.
BTW, Rojac isn't a marine tooling company ... they have a load of CNC machines and machine plugs and dies etc for the likes of AirBus and Aston Martin, as well as ROCAT!
atb ... Christopher

 

Christopher,

It's a sincere pleasure to meet you. I'm very impressed by your site and progress with the Rocat.

Sorry for not asking you directly, but over on this side of the pond, manufacturers tend to be a lot more secretive about such trade secrets, so I'd perhaps wrongfully assumed you might be reluctant to delve into details.

It was also my impression that one-piece closed-mold construction was a more widespread practice. It was my impression that surf skiis and similar long skinny hulls were made in one piece. Since the molding pros at Rojac were involved, I'd assumed they were the source of the closed-mold technology. I first found Rojac in a Google search for marine tooling mfgs (ie. plugs and molds)...I know they support a number of other industries.

I suppose it goes to show you how little I know about the state of the art. If it is your invention, then you deserve special praise for devising such a useful and practical manufacturing method. I'm sure there's a lot of "technique" that isn't shown on your site. Even if you haven't patented it, you might still be able to license it. A patent is not a prerequisite for licensing. IMHO, the technology could prove to be very valuable. Seriously, you should consider discussing this with a patent & licensing attorney.

If I have any specific questions on your methodology, I'll email you directly.

Best regards,

Tom McGuinness, PE
Pacific Tailboats

 

<smack! ...backhand accross the face for me>

lol...Actually you're right. I've managed to do things with some of my designs that weren't supposed to be done. One person/designer I've always admired is the late Verlen Kruger. His canoes are legendary and most of work was based on trial and error and not listening to "conventional wisdoms".

I have some question as well. I'll be in touch.

 

Tom

Thanks for your complimentary remarks ...

The whole patent/licence topic is interesting and extremely vexed. I have a patent on the ROCAT rigger, but a patent is only as strong as your ability (and will) to defend it.

I was, frankly, surprised that nobody else appears to be making hulls in one-piece this way ... it seems so obvious! It's only an ordinary vacuum bag on the inside of a closed mould. But it really does work a treat, and produces a wonderfully strong, light part. So, if I am the inventor, I am content for anybody else to use the method without let or hindrance from me.

"I'm sure there's a lot of "technique" that isn't shown on your site."

... not really, it's pretty much there in http://www.rocat.co.uk/boat/technology.htm

... if I am not patenting it myself, I certainly don't want anybody else doing so.

Be warned about the one-piece technique, though ... we have, so far, failed to get it to work in a complex shape. It works very well for the hulls, but not yet (after many tries) for the crossbeams.

"Since the molding pros at Rojac were involved, I'd assumed they were the source of the closed-mold technology."

Rojac come from a solid 'pattern-making' background, and they know their onions when it comes to machining shapes. But we were very much learning together about closed-mould composite tooling, which is something they are keen to become increasingly involved in.

atb ... Christopher

www.rocat.co.uk

 

Christopher,

I'm not a patent att'y, but do hold a couple of patents and have another pending.

Whatever aspects of your technique you've posted on your site may no longer be patentable...by anyone anywhere... due to it's public disclosure. However, you may still be able to license it. Rojac's interest in your technique should provide a clue. They sound like a potential licensee. I can't blame you for wanting to keep the greedylawyers at bay.

Don't worry about me...I'd never steal another person's intellectual property. I've been burned that way too many times.

Best regards,

Tom

 

Tom

"Whatever aspects of your technique you've posted on your site may no longer be patentable...by anyone anywhere... due to it's public disclosure."

... that was the general idea

atb ... Christopher

 

Christopher,

I would hope than anyone here who decides to use your technique will, at the very least, give proper attribution to the inventor.

I've been looking at various closed-molding technologies for the past couple of weeks and think your's is the best. And it appears affordable by smaller outfits like my own.

Have you considered submitting a technical paper or article to any of the composites technology and trade journals? Some good free publicity for your Rocat.

Regards,

Tom

 

I don't understand how the top of the part gets formed. The write up said the bag was partially inflated. Do you lay some layers on top of the bag and let the vacuum pull into place?

 

ah, hello...after being given the link,,I checked out the rojac site,,and sent an enquiry,,but don't seem to have gotten any response.
It seemed from the description that a pressure bag is INFLATED to hold cloth in place,,then a vaccuum is used to pull the resin through ---is this the case?
If this is the technique then the balance of pressures would seem to be quite critical in establishing optimal resin weight %'s....but maybe I got the wrong impression altogether!!

......oh a little more reading,and I see it's more 'rocat'-chrisoffer is the innovater with this than 'rojac'!?...question above still stands,though!...thanks!!

 

Have you considered submitting a technical paper or article to any of the composites technology and trade journals? Some good free publicity for your Rocat.

......professional boatbuilder magazine in the US would be a good place for this!

 

Gentlemen

What a flurry of questions.

Tom, you sent me some interesting questions outside the forum, but I suspect that the responses would be of interest to all, so I will answer them here after this post.

Tom said "I've been looking at various closed-molding technologies for the past couple of weeks and think your's is the best. And it appears affordable by smaller outfits like my own."

As I said earlier, this method works best with simple shapes. For your project, I wonder if roto-moulding is not the answer ... depends how crucial weight is. Check out www.wildthings-canoes.co.uk ... this guy has made his own roto-moulding machine and makes excellent, highly regarded, canoes with it. I will be using roto-moulding down the line for a cheaper, family, version of the ROCAT.

"Have you considered submitting a technical paper or article to any of the composites technology and trade journals? Some good free publicity for your Rocat."

Currently, I start most mornings at 0630, and finish at about midnight ... I'm afraid technical papers will have to wait for a while! But I will post as much information on the website as I can, which pretty well amounts to the same thing.

Jem said "I don't understand how the top of the part gets formed. The write up said the bag was partially inflated. Do you lay some layers on top of the bag and let the vacuum pull into place?"

The mould has a vertical part line (so the hull is on its side in the mould). Have a look at the 21 July entry on the http://www.rocat.co.uk/news/archive.htm page. We lay the glass on to the inside of the lid just back from the edge, then the glass in the bottom mould is cut 60mm bigger ... you can see it resting on the bag. Once we've closed the mould and activated the vacuum-clamping, we put a little pressure in the bag. The bottom mould glass then overlaps that in the top mould.

seamonkey said "ah, hello...after being given the link,,I checked out the rojac site,,and sent an enquiry,,but don't seem to have gotten any response."

Rojac is nothing to do with ROCAT ... they just CNC machined my plugs (from my CAD files) and made most of the moulds. This could explain why they have not responded to an inquiry about ROCAT.

and "It seemed from the description that a pressure bag is INFLATED to hold cloth in place,,then a vaccuum is used to pull the resin through ---is this the case?
If this is the technique then the balance of pressures would seem to be quite critical in establishing optimal resin weight %'s....but maybe I got the wrong impression altogether!!"

You are right to see an issue here. We have actually found that there is an advantage in divorcing the consolidation of the laminate from the resin infusion, and we are still working on the optimum balance. But, as soon as I can afford it, I will get a resin mixing/injection machine (such as the Plastech Megaject V, www.plastech.co.uk) to inject the resin under pressure, counteracting this with pressure in the bag.

BTW, I reckon this technique has only really become possible since the development of integral resin infusion mediums and good low-viscosity resins. We pulled the first hull using Rovicore, which worked really well, but was too heavy for our purposes. We now use Lantor Soric (which I highly recommend) between two layers of biaxial glass. The Soric first acts as a very efficient infusion medium, and then becomes a thin sandwich core.

more later ... atb ... Christopher