you will probably need to order some additional glass.....you can always wait until you receive everything and start your glass work to see how much extra you have and exactly how much if any more that you need.  fwiw, i have found in the past that CLC is usually pretty generous so first-time builders can get it done per their instructions without having to come back for more.  and if you are super careful, that can mean a lot of extra material. 

but if you just took them at their word, you have about 9 to feet of hull to cover that they did not plan for.  so if you went with 50 inch wide e-glass (4 or 6 oz) you could easily get it done with 4 additional yards (with some room to spare) if you cut the piece diagnally (so that the widest part leaves space for the thinest part.   its only about $ 7.50 a yard for the 50 inch wide...so your reinforcement isn't going to be terribly expensive.  if you are careful with your epoxy work, you will have plenty to wet out the addiitonal glass.  on the inside you done need to fill the weave..

fwiw.....if you are going to be a little agresive with it, i would paint your hull as it is a bit easier to keep it looking nice if you are going to be doing some refininshing work every year.

dyenl rubstrips are also a good idea for keeping the bow and stern knuckles in good order.....even though i think you are focusing on the right thing by glassing the inside of the entire hull if you were going to be rock-gardening.

h

 I built a Shearwater Sport, enjoy it much.  I only glassed as per plans, and the boat seems fine and plenty strong, but I certainly don't intend to ride a 4 foot wave into a blig black rock with it. In my opionion that is why they build plastic boats. 

But anyway, I question why glass the INTERIOR of the hull?  The same amount of extra weight might provide better reenforcement and protection by putting a double layer of glass, or use a heavier weave-weight glass, on the EXTERIOR of the hull.  Seems to me that more/thicker glass/epoxy on the outside would provide about the same amount of overall hull strenght as glassing both the inside and outside, but at the same time provide a thicker layer of glass/epoxy out there on the outside of the hull, and therefore less probability of any rock or whatever actually cutting or breaking through into the wood.

And BTW, even though it isn't very difficult to glass the inside of the Shearwater design, where the deck could be put on after glassing, even so it is easier to glass the outside of the hull.  You just drape the glass over the upturned hull and away you go - no puddling or interior angles, etc. problems as you can have with glassing the inside.  So thicker glass weave or double glass coats on the outside will be a slightly easier construction option, too.

Maybe you could really do some over-kill strength by adding longitudinal 1" square wood stringers along the center of each side of the bottom panels, or maybe (if not worried about storage) some partial-height bulkeads at the mid-points in the fore and aft floatation/storage chambers.  

Go whole-hog with these reenforcements and pretty soon you'd be able to drive a truck over the boat - but of course it will be 10 lbs heavier.

I respectfully differ with the un-nammed post above.  Adding additional glass on the inside of the hull will most certainly make the boat stronger.  Page 110 of Nick Schade's book, "The Strip Built Sea Kayak" has a wonderful discussion of various fiberglass schedules, which are just as applicable to S&G boats as strippers.  Nick says:

"...the glass will provide the most strength from impact on the inside, where it's in tension.  Glass on the outside provides abrasion resistance and protection from sharp objects." 

When you glass the inside, you might also consider going with S-Glass instead of the standard E-Glass that comes with the kit.  If you are not familiar, S-Glass is much stronger but also much more expensive.  It does not wet out as clear as E-Glass so it is not the best on exterior surfaces that will be finished bright, but it adds strength without adding weight.  I use 4oz S-Glass on the interior of my race boats to save weight, but you may want heavier.

One approach would be to buy enough (~6 yards) S-Glass to do the inside of the hull, then the excess 4 oz from the kit can be added to the high wear areas on the exterior.  I'd suggest glassing interior prior to intallation of bulkheads, but get them in soon afterwards.  

You may also want to reach out to CLC and/or Eric Schade for their recommendations.

Picture below is 4oz S-glass (C0427S) fom US Composits going into my Mystery.

ditto what mark said.  if you want impact resistance you glass the inside of the hull.  

abraision resistance is a different matter and while doubling up glass improves the situation, s-glass or e-glass is just not particularly resistent to abraison.   at some point, as the previous writer points out, if you routinely counting on banging/dragging it into rocks, a polyethelene boat may be the way to go.

i am also a fan of S-glass....but as mark said....its expensive..  but if an extra hundred or two is easily in your budget, it's fun stuff to work with.

h

   Thank you for the responses they have been great assistance and encouraging. I have been reading N. Shade's books and watching many of his videos on youtube been learning a lot! I thing i should of been a little bit more clear on is the boat will be primarily for surf, not as much gardening but you never know. A few other questions i have is im having a hard time finding a supplier that i can order 50" wide s glass.( most places it only up to 38")any suggestions will be great! And since im adding a skeg, should i do the cut out before or after i glass the interior? 

   Thank you for the responses they have been great assistance and encouraging. I have been reading N. Shade's books and watching many of his videos on youtube been learning a lot! I thing i should of been a little bit more clear on is the boat will be primarily for surf, not as much gardening but you never know. A few other questions i have is im having a hard time finding a supplier that i can order 50" wide s glass.( most places it only up to 38")any suggestions will be great! And since im adding a skeg, should i do the cut out before or after i glass the interior? 

CLC sells 4 oz 50-inch glass for $7.50 per yard. You select the width, 38" or 50" using the "Width per Yard" dropdown under "Ordering Options".

I've always cut the skeg slot after applying the interior glass.

Have fun,

Laszlo

For surf, the boat will be more than strong enough with the standard glass schedule. 

As Lazlo says, add the skeg after glassing both inside and outside the hull.

There are multiple choices regarding the skeg.  I have used both the CLC kit (Retractable Skeg Kit for Sea Kayaks: Improve Your Tracking - Easy Retrofit (clcboats.com)) on my Ch17LT.  It is very robust but requyires a hole in the deck and takes away storage from the aft compartment.  I have also used the KayakSport kit in my bride's Frej and my PP.  This kit is plastice to not as robust but it takes less space and is easier to retrofit.  Lastly, consider his kit designed by Nick (Chesapeake Light Craft » Petrel Play: Kit Option Details (clcboats.com)).

CLC kit in 17LT

KayakSport Kit in Frej

   Thank you again for the help! I did add 6 yards of 6oz of standard glass to my order. Hope everything arrives soon!

just another option i wanted to add re skegs.  i have used these from nash boatworks

https://www.nashboatworks.com/product-page/skeg-kit

it's 100 percent glass and a very easy, robust installation.  mechanically very simple and have never had one fail or jam up in over 15 years.  price is actually pretty good short of building your own.

for fun, you can also build your own skeg and swap out what they deliver.

first picture is the original skeg as delivered.  the second is replacing the delivered skeg with a self made carbon fibre unit