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Marius Jordaan

Vacuum bagging frames

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Hi all

 

This is my first post on this forum, please be gentle!

 

I'd like to know whether it would be feasible to laminate fibreglass onto frames using a vacuum bag setup, before the frames are built into the hull structure.  My thoughts are that this would make the glassing of the inside of the boat much easier, and any fairing of the formers should not be too much of a problem as long as the wood/fibreglass bond is good.  I already own the vacuum bagging setup, so was wondering if it would be a practical idea? 

 

Any ideas would be appreciated.

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Welcome to the forum.

 

It would be helpful if you described what you where trying to do and on what (make model and year). Frames typically mean a traditional build, in which case, bagging a cloth over them wouldn't be a good idea. On the other hand bagging reinforcement, tabbing or cleats of some sort, certainly makes sense.

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Hi, thanks for the reply.  My bad for not being specific. 

 

I'm looking at building a 16' power boat, and the basic construction is an eggshell crate structure of 3/8" plywood frames and longitudinals built over a jig, with 1/4" plywood sheet planking.  Planking gets sheathed on outside, as well as glassed inside, so do the frames and longitudinals once the hull is turned over and all the filleting is done- as per the attached picture.

 

Now I was wondering since I have the vacuum bagging equipment already, whether it would be wise or feasible to glass the frames and even the longitudinals before they are built into the structure. 

 

Unnecessary hassle or over complicating a simple build method?

 

Thanks

 

MJ

post-4639-0-31683300-1417339171_thumb.jpg

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   Welcome aboard, Marius.

   It sounds like you're trying to save labor and/or improve the final finish by using vacuum (I only stated that up front so you can tell me if I've missed the point).  If so, I approve of both objectives and I hope to learn from your project.  Would it be worthwhile to do a small-scale mock-up of the internal structure (say, one box section) with and without vacuum bagging to see which goes better?

   That box structure looks similar to the B and B Yacht Designs' Marissa.  I have admired the original build of that design and wondered how I would go about doing all those internal fillets and tape joints.  Maybe one of the B and B guys who has a vacuum setup will offer an opinion (Hey Alan, Are you listening? :) )

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   Welcome aboard, Marius.

   It sounds like you're trying to save labor and/or improve the final finish by using vacuum (I only stated that up front so you can tell me if I've missed the point).  If so, I approve of both objectives and I hope to learn from your project.  Would it be worthwhile to do a small-scale mock-up of the internal structure (say, one box section) with and without vacuum bagging to see which goes better?

   That box structure looks similar to the B and B Yacht Designs' Marissa.  I have admired the original build of that design and wondered how I would go about doing all those internal fillets and tape joints.  Maybe one of the B and B guys who has a vacuum setup will offer an opinion (Hey Alan, Are you listening? :) )

Thanks Ken

 

Your first sentence has hit the nail squarely on the head.  The filleting/taping will have to be done though, no way around that.

 

The design is an Australian one, called Sea Strike.  As it happens, I've been looking at the Marissa too, and have ordered the study plans for her.  Marissa is available in kit form, which is an attractive (but hugely more expensive) option.

 

If the idea is feasible, one will have to do mock-ups to determine the amount of offset to the notches in the frames/longitudinals of the egg crate structure. 

 

I need some input from the "pro's" first though, as I don't want to re-invent the proverbial wheel, and then end up with bigger problems than those which I am trying to work around.

 

It will be a while before I'm able to start an actual build.

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   Hi Marius,

   It looks like none of the vacuum bagging experts are chiming in.  I think maybe the design forum sees less traffic than other parts of Messing-About.  Maybe if you re-post on the main forum you'll get more input.

   In the meantime I can offer my opinion (which I hope you will consider useless since I've never vacuum-bagged anything but leftovers.)  I don't think you'll add significant strength or save significant labor by vacuum-bagging the frames before assembly.  The fillets and tape that you'll need to apply to the joint will do a great job of transferring a load to the plywood you use for the frames.  I think if you fillet and tape all those interior corners properly you'll have a very strong structure and if you then coat the exposed plywood with epoxy you'll have a structure that is rot-resistant.  Glassing the plywood will increase abrasion resistance but you really don't need that since the frames will be sealed into the interior of the boat.

   Since you've ordered the study plans for Marissa it wouldn't be out of line to call B and B to see what the recommendation is for sheathing the internal structure of the boat.  My gut feeling is that the internal structure is probably taped joints and epoxy coated (not laminated) frames.

   Please treat my comments here with a grain of salt since I'm just guessing and either re-post your question in the main forum where more people are likely to see it or give B and B a call (in my experience they've been pretty happy to answer the sort of question you are asking).

   And if you DO end up doing experiments with box sections to see how strength is affected by pre-laminating frames please share your results!

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Ken

 

Thanks for the helpful reply.

 

The plan does actually call for glassing the frames and longitudinals below the sole with 12oz biaxial fiberglass cloth.  I thought I may be able to laminate the whole of the frames (and longitudinals) using the bag.  This will take more setup time, add expense and probably lots more head scratching. 

 

As mentioned in my previous post, more likely I'm overcomplicating things, but since forums like these are usually great places to soundboard ideas, I thought I'd ask! 

 

I've ordered some of the cloth, and hope to have time to experiment over the Christmas/new year period.

 

My apologies for the fuzzy pictures.

post-4639-0-51192800-1417819517_thumb.jpg

post-4639-0-82636700-1417819663_thumb.jpg

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Oh well.  I was going to suggest getting together for a vacuum bag party to see what works on some throwaway material but you're halfway to Adelaide :)

The only problem I see with laminating the frames before building the boat is the question of whether the secondary bond will be good enough (I bet it will, but it's not my boat).

I wonder if it might be easier to tab the majority of the structure together (frames, stringers, planking) and then vacuum bag each of the cavities as a separate mini-project.  Just stick it all together using small tabs of epoxy and then fillet, tape and sheath in one fell swoop (but just one cavity at a time to keep things manageable).  Building the hull is just a small part of a boat building project. You'll spend as much time sanding as building so it might make sense to glass one little box at a time just to keep things manageable.

You better get on it before summer really takes hold though.  Epoxy kicks really fast at 45 degrees :)

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Ken

 

Yes, too hot already to work outside, which is frustrating to say the least.  I was hoping to start around February/March, when the temperatures are down a bit.  Slow "tropical" hardener is going to be required.....  I also need to find a temporary storage facility for my current boat, as I'll be needing the space it occupes for building.

 

Vacuum laminating " flat" structures in a bag is easier.  The use of a peel ply over the saturated cloth should leave a finely textured surface, so in theory getting epoxy and tape to adhere to the pre- laminated parts shouldn't be a problem.   I'm keen to do some smaller scale trials to see how it goes.  The materials are expensive, and except for the nylon bags, not re-usable, so a "feasibility study" would make sense.  But I am curious, and you know what happened to the cat!

 

Thanks for your input, it is much appreciated.

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