Boat Builder Central - Builder Forums

In looking at the the PG25 for use in rough water and maximum rigidity in all conditions I have considered using double bias +-45/45 as one layer and 0/90 degree biax for another. I am hoping that by using this schedule I will have strong longitudinal strength from the 0/90 and latitudinal strength from the double bias. I am planning on using this on the bottom as well as on the inside bottom before installing the stringers and frames. I believe that I will increase the structural strength as well as the rigidity of the boat and add strength to the monocoque structure for many carefree years of enjoyment. At times on the Gulf we have very short period rough water that are not ground swells. If I am wrong in my assumptions please tell me, as I see this as an enhancement to the longevity of the boat by having a stronger hull with less movement in the structure itself thus less stress to the hull.


HWS

There is really no need for this. If you want put a double layer of biax on the outside bottom. Jacque builds into his boats a safty margin based on his experience as a designer at Cigarette and Pusuit. They can more than take on anything you will encounter for years and years to come. The extra fiberglass your proposing just adds unnecessary weight without doing what you want.

Adding fiberglass is not all it's cracked up its to be. If you really want to strenthen the hull add partial frames between the frames in the design, especially the last 6-10 ft, also up the sides to the bow. These add less weigt than the fg that you propose and will give you a very stiff boat.

Tom

First of all, the lamination schedule given in the plans is more than adequate.

Plywood has stiffness in 0/90.

If you insist on using more glass, just use another layer of 45/45, or a layer of woven cloth. Either way its overkill and will ad unnecessary weight and expense to the boat.

Tom is correct, stiffeners or half frames will give more stiffness to the hull, but again its completely unnecessary

Build yourself a "v" section of the boat use two pieces of 3/8", 2 layers of tape each side of the joint then baix on both sides - try to flex it and then decide if you want to add more glass

That answers my question 100%. I knew that I would gwt the right answer by asking. Thank you Tom and Joel, I did not want to overbuild, just trying to make sure I do the best job possible.


Thank you,
H W Slater

HW some of us have put a double layer of Fg on the bottom. We have done this basically as a puncture resistamt llayer. Not as as a stengthening layer.

I don't want to mislead you from my post above, the second layer only adds a certain % of strengthening over the 1st layer. Maybe 75-80%. The real strength comes from the combination of the outside layer of 45/45 biax, the plywood and the inside layer of 45/45 biax.

Stiffening the hull comes from adding the partial frames as I mentioned in my last post and Joel confirmed.

Note these boats are based on interlocking parts that make them extremely strong to start with. Adding the partial frames just makes them evem stronger.

Tom

hwsiii wrote:That answers my question 100%. I knew that I would gwt the right answer by asking.

But why did you assume that we design weak boats?
Ours are designs for amateurs but not designed by amateurs.

Ours are designs for amateurs but not designed by amateurs.

I think Im going to put that somewhere on Cloud Cap....

My boat gets beaten to death, driven well over its intended speed, sometimes with as many as 8 occupants, well above its suggested speeds. I use a motor that is too large. I carry excessive loads. We use the thing for wakeboarding of all activites! It gets beached on almost every trip out on very steep banks

They are tough as nails, go with the standard lamination schedule.

E

Jacques, I thought I was asking a reasonable question in reference to a lamination schedule. I did not assume or imply you designed weak boats, I was just asking if I used the biax as well as double bias, would that not increase the longitudinal strength. I am sorry you took that as an indication that I thought you designed weak vessels, that was not my intention at all. I will be more careful with what I contemplate and ask in the future.


HWS

HW, don't worry about it, ask all the questions you want. That's what the forum is for. Just keep in the back of your mind that all these boats are designed to meet all NMMA requirements and that Jacque has been doing this for a long time. Including stints at Cigarette where boats reached 100mph and Pursuit which are concidered one of the top offshore boats built, before starting this enterprise about 20 years ago.

You can make modifications to your boat and that is not a problem, add anything you want. Just don't change any of the structure that is in the plans. Just what you proposed this time was overkill.

Keep asking questions and we'll help you get the boat you want.

Tom

Thank you Tom. I didn't include that I also intended to use the biax as a filler between the tape joints at the keel and the chines as a way to help fair these areas up to the height of the tape joints. I made an error in not stating that as part of my intentions in my post as I forgot to include it, but I did state that in the Topic Heading. I do not like to ruffle anyone's feathers, especially Jacques, as I do believe he designs a premium product or I wouldn't be here. I am not always good with my wording or trying to transfer my complete thoughts into words online. I do not take enough time to "ponder" how my statements can be construed as Larry says. When I have an idea that seems reasonable I ask, that way I get other peoples recommendations and/or reasons not to do it. In the long run it helps me to make the correct analysis and judgement call of what I should do. This drawing shows my thought pattern on this and it made sense to me at the time. LOL






HWS

Filling between the tape joints with glass is a valid technique, indeed the Cracker did it on his OD18 bottom. I would think that it is heavier than fairing compound,but will help with the fairing process.At the end of the day, I think it would be up to you as to wether it is a trade off worth having.
Just my 0.002.
Steve

Yes, I did the same thing for the same reason on my OD18 using 12oz. biax. I don't know if it's any heavier than a lot of fairing compound, but I'm sure it's stronger, and gives another abrasion layer against the rocks and oysters.

Nothing wrong with you question or idea HWS Jacques lamination schedule provides more than enough strength, but if you anticipate heavy and hard use a little extra protection is not out of line. It will add weight and cost, an OK trade off for me and my intended use.

I do not like to ruffle anyone's feathers, especially Jacques,

He's just joking with you. You aren't ruffling feathers

hwsiii, do you have the plans and did you look at the lamination schedule?
There is already a lot of fiberglass there and with the overlaps that we specify, you will have extremely strong chines, keel and transom seams.
As Joel wrote, we get the 0-90 fiber orientation from the plywood and add the 45/45 to create an isotropic material.

I know that many builders add a layer or two. That is not a major problem.
What upset me were the words "to use in rough waters and for maximum rigidity". That boat is designed for use in rough waters and all our boats are incredibly rigid thanks to the monocoque structure.
Contrary to production boats, in our boats all parts including frames, sole and deck participate in the structure to create a very stiff and strong beam.
In a production boat, the deck and sole are tied to the liner and do almost nothing except looking pretty.

You, like most of our builders, will be surprised by the strength and stiffness of our hulls.
If you feel better with one or two more layers, please do it. As long as you do not excessively increase the weight, it's not a problem.
You will feel better about your boat and we may sell more fiberglass.


PS: no bad feelings here. Sorry for the outburst.

I plan on doing exactly the same thing do to the shifting sand bars and floating logs on the Mississippi. I want the extra protection. So there are reasons for doing what you propose.

I am also using Meranti on the bottom panals since there is very little bending in the C17 and it is stiffer than Okume. And all Meranti inside.

Tom

I clobbered a deadhead last year that, once we went back to look at it, weighed probably 50+lbs. Hit just left of the centerline of the boat at over 25mph by gps. Unintentional, and a helluva shot to the hull.

I have to say I was disappointed in the durability....



Of the paint....

Not even so much as a dip or crack in the glass, smooth as a baby's butt and just needed paint touchup.

E

Yep. I hit a submerged oyster rake in my GF16 running wide open, 30 mph. Picture a pile of rocks with razor sharp edges. It sounded terrible and I thought it may have ripped the bottom out. It would have on a fiberglass production boat. But surprisingly no leaks developed and we finished out the day.

I was scared to look at it when I pulled it out, knowing the glass was destroyed. But no, I was amazed to find zero damage except to the paint. The glass was not even scratched. Not a chip. That was 2 layers of 12 oz. biax. It made a believer out of me

It was my fault for not choosing my words better Jacques. I have not purchased the plans yet, so I have no idea what the lamination schedule you designed is. I was theorizing on the concept I was thinking about. I am sure it will help in fairing the boat and add more strength than the quickfair, but I was sure I had not considered all of the variables involved, and one of the parts I hadn’t thought through Joel mentioned, the plywood is already at 0/90 degrees. I have been to many other sites and looked at their designs, but I did not feel as comfortable as I do here, and you actually include things like the study plans and designed speeds with the required horsepower (free) to help us make a better informed decision in the end as to what boat better fits our intended uses. So if you would please take my posts as the rambling thoughts of a man who is just trying to get up to speed on the new techniques (to me) in boat building. If I had to build something like the PG25 the old way, I would not even give it a thought, I just would be buying something in the production models. Although the way the market has been for a while, I can’t stand anymore, or I won’t even be able to build what I want. I am a research oriented individual and have to know how and why things work and don’t work.
Knowledge is something you can never have enough of, I only wish I had the wisdom to go with it.

HWS

HWS I can only speak for myself but ask all the questions you want and don't be hesitant to speak your mind, as you can see, we do.
Questions are the only way to learn, and you would be surprised to know, you are not the only one to learn from your questions. Some folks are too timid to ask but are probably glad that you did. As you can see, 18 have responded but over 400 have read the thread.
Glad you are with us, hope you enjoy your build.
Daddy

I am thinking about building a 15 foot, stitch and glue sailboat with a 3 1/2 foot beam (Enigma 460). The plans call for 2 layers of 9 oz tight weave fiberglass cloth for the bottom, inside and out. I was thinking of using 2 layers of 12 oz biax (45/45) glass fabric instead, which I see is sold by Bateau. Will this give me a stronger boat? I understand that less resin is needed when using biax, so the boat should be lighter as well?
What do you guys think?
Thanks,
Dave

12 oz biax will use about the same amount of epoxy (per same weight) as 9 oz cloth. It will be significantly stronger however.

I would use an alternative: one layer 12 oz 45/45 biax, then over that one layer 6 oz woven. This will give you the same amount of glass called for in the plans, but it will be stronger and easy to fair. Do all the glass in one day and it will come out very smooth.

joel

Joel, what do you think of using the 4 oz. Dynel as a finishing cloth?
Daddy

Personally I would not use it: I hate sanding it, it takes more epoxy to wet out, and it has no real strength other than abrasion resistance.

Dynel is quite tough though and as a way to add some abrasion resistance over wood (where you do not care about adding strength) it certainly has its place.

Is a valid option, just not what i prefer personally

I have used it on decks and like the way it mimics the traditional look of canvas plus it is pretty good non skid without adding anything to it, I take your point about not adding strength.
Daddy

Daddy wrote:Joel, what do you think of using the 4 oz. Dynel as a finishing cloth?
Daddy

Use a finishing veil instead like our 3.25 oz.
http://boatbuildercentral.com/proddetai ... th_3.25_50
Not only does it produce a very smooth finish, absorb less resin but also it adds strength. Dynel will not add any strength.

Finishing that 3.25 oz fabric is a DREAM. Used it on the rowing shell, 2 coats to fill the weave of unthickened, and it was golden.

E