Hard Chine composite, preglass panals before or glass in place?

You can fiberglass the interior surface (concave) and then bend it. After you fiberglass the outside, the job is done.

 

You should glass the panels first with the Kendrick Scarab method.

If the panels are attached to the building frame before they are glassed they will not hold a fair shape and need lots of filling and sanding.

10mm honeycomb panels that size will be very floppy without glass.

I helped put together a scarab 16 float hull with 10mm unglassed honeycomb panels with the intention of glassing the entire exterior in one go to reduce the taping. The panels were so floppy and out of shape that we ended up giving up, taking the panels off, glassing them both side on a flat table and then replacing them on the building frame. Worked perfect, perfectly fair panels only needed to fair in the glass tapes.

Hope this helps, DAVE

 

Make a big flat bench and pre make everything using paterns exactly to shape and size !!just as if it was a stitch and tape job . remember each pattern for the sides and bottom panels you can make a port and stb
Step the core back at least 80mm back from all edges so you have good glass to glass bonding area and use peel ply for all you finishing work . Tape the joins with tri axle glass 45/45/90 so the three layers go across every join , If you are clued up you cand also make a shallow recess along all the areas that have to be taped so its just rip off the peel ply and glass after final final placing of the sheets in place . What id you galss lay up for the boat ?? Make the glass just a fraction oversized to the patterns Laminate the outr skin and then do the core on top remember the 80 mm round all edges and shamffer , and round , and sand the core edges then place and vac bag in possition . depending on the thickness if the inner skin you can simply skin the inside with just one of the two layers and when its all done add the last skin later
What is the thickness of the core you intend to use ??
Treat this build as a stitch and tape job but you are using glass panels instead of plywood !!. same things apply !!. If you have a nice bench you can gel coat the outer surface so a part of that job is already done . Making a cabin can be done also using stitch and tape method remember to try and make a recess on the outside so you dont have to grind it so you are able to glass and joins and edges etc etc . If you think a little you can make your deck in two parts with a central join, then glass the outer edges to the hull
cabin sides and combings all in one length . saves having to make mould foe anything and just have to make one pattern for one side and turn it over for the other side !. as you get on with the job you will see ways of making all the bits for your boat all using the same method . You could us unfussion to get the weight saving but personally id just laminte the panels and vac the core!! but peel ply everything inside and out makes a excellent finish !!

 

That helps a lot. Thank you!

Was there any issue with them being too stiff to bend? My primary concern with that method was ending up with a strip that was so stiff it wouldn't bow into shape properly.

 

I'm not entirely sure what you mean by stepping the core back. Are you meaning to remove a thin layer of the core? I don't think I can do that with PP honeycomb. I believe the factory veil on it is bonded much better than epoxy will stick to the core and removing it will make a weaker bond. I may have to live with a slightly raised area where the tape goes on the joints and fair it.

 

I think this is what tunnels is trying to explain. Lloyds has many design details that help make a good lamination.

Since your choice is honeycomb and you are using a male mold, this will be difficult to do. You have to fill up the honeycomb (at the corners where it will be stepped) with microballoons putty, then scarf it by grinding.

Sharp corners or chine are always reinforced by a factor of 1.5 (1.5x the thickness of the original laminate) because it is the weakest part. If you dont scarf it, you will get a bulge on the outside and you won't be able to fair it succesfully. Personally, i dont mind the bulge on the inside but on the outside, there should be none.

One way to make it simpler is to eliminate honeycomb core at the corner/chine and make it solid glass laminate at least 1.5 x thicker than the outer and inner skin laminate combined. As illustrated in the left hand coulumn. you have to increase the laminate layers though as it is not illustrated.

 

Ok. I think I'm with you. I think I'm OK with the bulge on any of the concave joints on the outside. That should fair out pretty easily. If you look at the pictures below there are 4 convex joints below the water line. I think it would work to put two full layers of glass over the whole portion below the waterline (a bit more than plans require) to add some durability because I sail in thin water a lot. Maybe one of the layers should be kevlar?

That only leaves one convex joint that is well above the waterline. Possibly on that joint I will be able to get away with just having a slight bulge at the joint. I'll have to do some testing with the honeycomb to see how well epoxy will stick to the polypropylene. If it sticks well, then the vail bond may not be necessary and I can step the material a bit at the joint

 

I should add that there are instructions in the plans, but I'm making some changes to the design so I should probably call it a "Scarab 18 like" tri. The main being that I'm probably going to build different beams, and am 99% sure that I'm going to re-design the beam/ama joints so that the amas are removable. I want to have the ability to have a more modular system so I can play around with different ama designs in the future, like building some wave piercing ones for example to try out.

 

There was no problem with the panels being to stiff to bend, the hulls curves are really not that big, 10mm honeycomb and 400gsm glass panels over 5.5 metres bend around the frames really well, perfectly fair, and once taped together then the stiffness really shows,

Also, the taped joins are really not difficult to fair into the main panels, afterall 400 gsm double bias tape is not that thick once laminated. Use peel ply and you'll have no troubles

Regarding the beams, I'm not sure of your plan for the beams, but the solid glass beams to me look quick, simple and easy (speaking as a mould maker so I have plenty of experince with glass laminates) however it could be daunting for a less experienced builder (no disrespect intended, just dont know your background)

Hope this helps DAVE

 

Glass ! how many of you really understand what you are working with ???

Bendy GLASS sheet and panels ! Glass and resin are wonderous materials to work with but takes a little imagination and inventiveness and a wide open mind ! dont be afraid to not only step out from the box you are in but kick its walls down flat and open your eyes
Its possible to wrap glass round a 50 mm radius or down to 30mm radius but is a little more diffcult or make panels for the construction of a boat hull that will bend with a beautiful completely natural curve that could be more than 10 meters long or even longer .
Its possible to make panels that are foldable in any direction and make the bends with all differant curves and radiuses .Still have'nt mastered 90 degree bends 100% but its possible just need a little more imagination .
While working in Korea i showed them how to make all the face panels for the inside of the new boat we were building in one great long length and to have no joins just the ends where it was attached to Bulkheads at each end !
I called it Origami glass panels . Its something no one has ever thought of or even heard of . its basicly understanding the materials you are working with and the limitations of differant glass you have to work with ! knowing what you can do and how you can use it and when you can do some of your bends .
Glass panels can and will fold just like sheets of paper .
The young Korean lady (Su Jung Lee ) Boat designer i was working with at the time cottened onto what i was demonstrating in a matter of seconds and by the time i washed my hands and been to the toilet she had sat at her computer and drawn to scale a series of panels that could fold and unfold .
The boat we were working on at the time had the deck already attached and there was a limited size of the companionway so the fold sequance of Aany panel that was over almost 12 meters plus long and be able to unfold it in a in a very limited space was a enormous challenge , but with computer animation and a mind thristy for Knowledge she made it work in a very short time that would have taken us hours to work out . Working with bright people over my life time i have learned to never take things at face value and to swing the doors of you mind wide open and prop them there and never stop learning !!
After reading what i have written there going to be a few that will have not the foggyest idea of what i am saying , and others that are so regimented in there ways and methods they cant see any further than the end of there noses but some where just one will get the idea and run with it i hope .

What influences bend or curve ?? Thickness , tension , number of layes , type of glass ( now this has to be the most important thing of all ) the amount of glass and the oriantation of the fibres .
Uni dirctional glass you can literally tie in knots and i mean knots !!
45/45 glass will give a differant bend to 0/90 exactly the same weight of glass or even 90/0 .
So oriantation is important ? The way the glass runs is going to determin how your panel will bend and how much it will bend and where it will bend also the number of layers being used !!, how the glass layers are stacked with these diffeant layers of differant glasses determins also how a panel will bend . Note i said where to get bend !! the placement of diffeant layers of glasses within a panel can change the whole shape as well .
Had a great long narrow panel the needed to be made and fitted in one piece !. The challenge was it had twist in a couple of places so this was a seamingly impossable thing to make but with a little thought and a lot of hands we fitted it and clamped it in possition to let it cure to the shape . Once gelled it was eased of the work bench and ever so gently carried and lifted up into its final resting place . Using the cure rate of the resin also can be used to get to shape panels with out lots of tension and pressure involved you have a small envelope of time to get the work done so have to be well rehursed and know what you are doing !!
Do you understand everything about the materials you use ???
Are you always familiar with the resin gel time and catalyst % and the glass and the weather and the temprature plus humidity all day when you are working etc etc !!

 

Wow there is some one out there that thinks like i do !! You been working with glass for a while by the sound of it !! welcome !!
The beam thing is really quite simple and personally you making a glass boay DONT USE WOOD specially under floors and places that will stay wet even if its sitting on a trailer out of the water !! wood gets wet , get heavy , goes rotten , no matter if you soak it in resin !!!
I have a boat made 1975 and the bilge is dry as a bone all the time I have no holes in my hull !! no drains!, no nothing !!

 

I wouldn't pre-'glass the panels, but arrange your core on the mold first, cutting and trimming where you'll need solid laminate and insuring good alignment while the panels are easy to manipulate and cut. Once satisfied with the arrangement, then the outer laminate goes on in one shot, making a homogeneous hull shell. Flip it, install your structural core elements, then the inner laminate. Why make more work for yourself and employ mechanical bonds, when you can do each task all at once. By this I mean, set up for core work, install and trim the core on the mold, then set up for goo work and laminate the outer skin. No going back and forth. Flip and repeat the process, doing the additional core assembly, then the inner skins. This pre-made panel thing isn't any advantage, unless you're looking to produce a few hulls each week, at which point you'd want very precise panel templates, so you can hack out dozens of perfect panel blanks and skin them.

In other words, if making pre-skinned panels, you'd set up to trim your cores, then skin them, making allowances for bonding, then it's back on the mold, then bonding the panels on the mold, of course after more trimming. Seems a lot of back and forth to me. Fitting the cores, then skinning without regard to having to pull them off or put them on, or allowances for chine bonds, etc. Screw that, if I got cores that are well fitted, why would I want to add a few extra steps? Sure it's easier working down hand on a flat surface, but you could make your mold rotate, so that you're working in a reasonably down hand position anyway, without having to disturb the good core fits in the process.

 

Thanks for the compliment, glass has its place but I love timber epoxy also, all materials have their own place if done correctly I suppose

DAVE

 

Tried this system on the 16 foot version, worked like crap, cant see how it will work on an 18 foot version. I'm not sure if you are familliar with the Scarab construction method but the "mold" is really a very basic mdf building frame. Unglassed panels are simply too floppy to hold a fair shape, unless alot more work is done on the building frame (stringers etc) to keep the panels fair.

If the panels are cut to the proper dimensions no trimming is needed, this preglassed method is used alot in Australia for amateur construction, from small trimarans like the Scarabs to larger catamarans from the like of Schionnings, Oram, Grainger. Seems to work for them.....

DAVE

 

Throwing in a few extra station molds or running some stringers seems a lot easier to make a hull shell, then trying to make a core act like plywood. I'd want to do the core, then the skin, not go back and forth, better control on bonds too, but to each their own I guess. Again, if I had a bunch to make, I'd consider some sort of assembly line approach, but as a one off, I'd want to streamline the process as much as possible, doing one process, then on to the next, not back and forth.