Overlapping smaller epoxy-infused composite sections versus one continuous piece

Need to know if this is a bad idea. I have given up on my resin infusion/vacuum bagging for my 11’ canoe project. I’ve got a heavy tandem canoe and would like to build a much lighter one using it as a mold. In this case, I’ll be working with a male mold. Not expecting perfection. My plan is to make patterns with release film and cover the boat with it. I do not trust using wax or other release agents. I don’t fully trust them on an old scratched up ABS hull. I’ll rotate the boat doing bottom first, then each side. Letting each side cure before doing the next.

I plan on vacuum bagging smaller sections on a flat surface then transfer them to the mold. Overlapping about an inch or two. I’m working with 11.5 oz carbon fiber I bought almost 25 years ago for $6 a yard, 60” wide. I have 25 yards of it. Dry it is stiff as a board. I vacuum bagged a one foot section today and it will be easy to work with.

My only concern is the possibly of a section separating since they will not all be added at the same time wet. Each of the three sections will be done while each piece is wet.

So, what’s the opinion on this? Thanks. Alan

 

Why not just use a peel ply for the seam overlap?

 

Why not do a continuous piece?
Or at least two halves. Shrink wrap or packaging tape over the plug?

 

Thank you. How does one manage a 16’ piece of vacuum bagged resin infused carbon fabric? Can it be rolled up and not become a mess? As for packaging tape or shrink wrap, I’m assuming these would have to have a release agent applied. Is that correct?

 

Did not think of that. Thank you.

 

Typically... packing tape, vacuum bag film, sheet plastic film...do not need an additional release agent with epoxy. I have gotten into trouble trying to replace PVA mold release and mold release wax with 'home remedy' substitutes (vegetable shortening, lithium grease, car wax, etc.) where the epoxy gets enough of a bite to grab the mold.

I have never done this idea of a vacuum wet out and transfer to a new form, I think I understand that it is to help get the stiff fiber into a pliable and wetted state.

I have done 13' (4 meter) off-project wet-outs of fiberglass fabric on polyethylene film and rolled them onto a 4" (100mm) PVC tube and unrolled them over the form. There is some loss of resin and it can be nerve-wracking getting things back to straight working by yourself with faster-curing epoxies. The same project had other patches of carbon fiber added manually, which got buried under plain weave to minimize black sanding dust later down the line.

My preference is to work right on the form with a fabric can can drape enough to get the job done and/or add relief cuts where necessary.
Weigh the cut fabric to help determine a good starting amount of epoxy. Better to be slightly short and make a little more at the end than to have a large overage heating up the cup.

Maybe the best trick would be to have a friend or two on site to help wet out and 'flip' the long fabric pieces onto the old hull, regardless of vacuum or free-air wet out.

There was a surfboard maker Jimmy Lewis who would basically shrink wrap hand laminated projects without vacuum, the technique was nicknamed 'poor man's vacuum' or something like that, I am sure there are YouTube videos somewhere. Whether it's a good fit for this project or not I cannot say but the method is interesting either way.

Treating a to-be overlapped edge with peel ply, then removing the peel ply to make the next lamination, is a great idea.

 

I vacuum bagged a one square foot piece of carbon. Dry is weighed 36 grams. Finished it weighed 46 grams. 78/22 ratio. Part looks fine.

Thanks Tops. Still have some experimenting to do. I need to test another piece of carbon. A one foot square piece vacuum bagged yesterday had a fabric resin ratio of 78/22. The part looks fine. I thought the super low end was more like 70/30 with 60/40 being fairly common. The next test I will add more resin.

 

If my reading of this is correct,it seems that we have a poster who is proposing to infuse a piece of cloth and then transfer it to the mould.Surely the point of infusing is to locate the cloth in place and then infuse it while it is held to the desired shape.Have I misunderstood?

 

I’m not infusing. I’m doing hand layup and vacuum bagging it on a flat surface. Then transferring it to a male mold. I’ve gone the resin infusion and vacuum bagging route and it’s too stressful. For me, this seems like the logical next step to building a light canoe.

 

I’d be inclined to wet/roll in place, skipping the vacuum, but squeegeeing off excess resin as much as possible.
You’d probably need three sets of hands, but you’d not be in such a hurry. You could catalyze smaller batches of resin as work progresses, keeping a wet edge, but not necessitating getting the whole piece right in one go.
Pictures of the piece would help this discussion.

 

May I ask what exactly you hope to achieve by that? Are you hoping to have a bag all around and drape it over the canoe while still wet and under vacuum?
You say the hull is ABS, take some fairing compound and smooth it out, epoxy does hold on ABS. If laying up big pieces is to stressfull just work in stages directly on the mold, lay the dry fiber on the mold, wet it in place and seal the bag to the mold. As said you can shrinkwrap the mold if you don't trust wax.

 

I am vacuum bagging on a flat surface, removing the bag, then transferring the fabric to the mold. I have done three vacuum bags on a canoe mold and they all failed. Not going that route again.

 

I don't know whether it is possible to edit a thread title,but it might be worth doing so and substituting the word infused for something else,as the pieces of cloth won't be getting infused at all.It is simply a case of setting out the cloth and then transferring it.It can be done and has been done,but it might not be the best solution as the shape of the canoe will almost certainly require the cloth to be tailored with a few darts.As mentioned above it would be easier to lay the cloth over the canoe and begin at one end-then work along using several mixes,which would ideally be prepared on demand by an assistant.The tailoring can be done on dry sections of the cloth and cleaning the scissors will be less of a messy process.

This being a design forum I won't say too much about the ethics of the operation being contemplated and the expectations of the designer of the original.I hope the matter has been considered.

 

There’s nothing illegal or unethical about what I’m doing. It’s a 45 year old canoe and the company (Mohawk) is no longer in business as a canoe manufacturer. The below thread has a very detailed response relating to the 1998 Vessel Hull Design Protection Act .

Is it legal to make composite canoe off an existing design? https://www.canoetripping.net/threads/is-it-legal-to-make-composite-canoe-off-an-existing-design.127519/

 

What do you expect from the vacuum step then? Once you remove the bag there will be no consolidation going on anymore the fabric is going to relax again, especially with you handling it around. There will be some excess resin removal but far less then hoped since you won't maintain the vacuum until gel stage.
Why not skip the vacuum altogether and just hand laminate in place followed by peelply and dilligent hand rolling? If the fabric is stiff it's common to wet the fabric on a piece of plastic on the table and transfer it afterwards.
Anyway, my advice is you try your method then do the same piece again by hand laminating in place with peelply and weigh the two cured samples to see if there actually is enough weight benefit to warrant the aggravation.