stringer replacement?
 

a question for all you experts. I am replacing some stringers and I have two questions.
1= if you only have 2 feet of a 8 foot stringer rotted what is better? replace the bad and overlap the glass? or replace all eight feet?
2- I have stringers that are 1/2" plywood but they measure 8'6" long how do I make it one solid piece of wood? or is it ok to just butt it together?
any help would be great
Keith

It depends on the situation. You should all ways scarf your joints and radius your angles. Google Professional Boat Builder magazine. Lots of good stuff.

1- i would replace the entire stringer. Its not a whole lot extra work for piece of mind.

2- I make stringers by laminating my own using plywood thats half the thickness of what i want my final thickness to be. Most of mine are 3/4"+ so i use 7/16" and stagger the butt joints. I have made twenty plus foot stringers using this method. Your is kind of an odd case though because you are just slightly over eight foot. I would cut four pieces aprox 52 inches long and then cut one in half length wise, arange them as shown. It puts the greatest distance between the joints. Bond them together using 1.5 oz fiberglass mat sandwiched between them and do all your final cutting and fitting after its constructed. Basiclly build it over dimension and then cut your stringer out of that (hope this makes sense)

What are you working on? just curious

thanks Dave, It does make sence.
Im working on a 89 Panther it a big project but im haveing fun doing it.
If you don't mind I have some more questions for you.
Would or do you always laminate two pieces or do you use one where you can?
What kind of wood should I use?
I planned on marine and I have already got it for the transome but not the stringers yet.
Im using the medium set epoxy from us composites and they said not to use the once and a half mat but use there bi-axle cloth because the mat doesn't wet well with epoxy. Is thet true?
thank you everyone for the help.
Keith

I use outdoor rated plywood on standard stuff and marine ply on higher end jobs although most people in the biz just use the outdoor stuff.

I only laminate my own if the stringers are longer then 8 foot. I noticed you said you had some that were 1/2". I use 3/4" minimum for anything structural.

Yes with epoxies do not use chop mat, i didnt realize you were using epoxy. The best fiberglass to use is 1800 Bi-Ax, its the same as 1808 but does not have the mat stiched on, it wets out much easier to and you can also sandwich it between the wood. The standard 1808 is difficult to wet out as well because of the mat(08) stiched on even though its binderless. You do have to be a little more careful when handeling 1800 though, after its cut to fit it is easily distorted so handle gently.

fire away with any questions ya have thats what this section is for, post pics to if ya can :cool:

Dave
I'm also going to be doing a stringer replacement job on my 27 Magnum. I'm going to change it from a twin engine TRS set up to a single Bravo set up.
When I have the stringers cut to fit (including a 24 degree angle) can I use 5200 to bond it to the hull before applying glass over the stringers? Is two layers of 1708 or 1800 enough? How far out should the glass be tabbed from the stringer?
I've learned alot by reading your post and helping everyone with fiberglass issues!!
Thanks!
Bob

No dont use 5200 under the stringer. I usually fit them reasonably snug and trowel some cabosil in the gaps. If it needs some support maybe do a small tab on the ends to keep it stable. I cover the stringers with two layers of 1808(using poly) or 1800(using epoxy) and maybe an extra layer or two at the tab joint out about 4 or 5 inches.

If you can find 1800 it makes using epoxy a lot easier. Post pics :cool:

Thanks Dave!

Fast Shafts , if you need a little support to hold the stringers in place instead of 5200 try using some wood hot glue at the ends ,and might i suggest using three layers of 1800 instead of two because most high performance boat Co's like Skater use 3 layer's of 1800 for there initial layup on stringers . Fast Shafts considering you are going to go with a single motor/drive setup (bravo) just curious how much HP are you thinking of running ?

heres what I have going on.
Dave us composites sent me 1708 glass will that be ok?
I cut into the stringers where I could get a good measurement and they are 3/4" not 1/2".
Im replacing the two main stringers in the cabin, the outside ones are good, all four in the middle section of the boat, the bulk heads at the helm and in front of the engines.
I have to build a new stringer in the middle of the engine compartment because the person that had it before me cut it out to make the boat a single. I am putting it back to twins.
I found alot of oil in the cabin under the liner do you have a god way to clean it up without hurting the hull?
thanks again Keith