PDA

View Full Version : Newbie question- Lap Joint bonding



Centerpindrew
03-17-2017, 09:40 AM
Hello everyone,

I am a beginner at wooden boat building. My first boat I am going to build is a 15' wooden drift boat. On the plans it says to epoxy the ribs/frame lap joints but also shows fasteners in place as well (never removing them). So after reading over 1,000 posts on the internet, I am officially lost with what to use for a bonding agent at this point, ie: Epoxy, PL Premium, etc. Some say stick with epoxy and some say use a polyurethane..

I donít have a problem spending the money on epoxy for this step but is it truly worth it for the rib framing lap joints? Again, they will be held in place with fasteners also and the inside of the boat wonít be exposed to constant water.

Not to mention that itís still cool weather in Upstate NY and I am working in a cooler work shop, not 70 degrees!

Any information would be excellent! Thank you all.

Peerie Maa
03-17-2017, 09:50 AM
The mechanical fasteners hold the joint in alignment until the glue sets. Leaving them in saves work.

Use a reliable waterproof glue, a lap joint should be strong enough with whatever glue you use, but ensure that it is waterproof, and if your joinery is not cigarette paper accurate, ensure that it is reasonably gap filling. It may not have water slopping over it every day, but it will be in a wet environment, so must be waterproof.

P.S. Welcome to the Forum. ;)

Gib Etheridge
03-17-2017, 10:20 AM
The designer most likely calculated for the strength of a full length continuous bond, you should do the same. You'll be glad that you did when you hit rough water.

Epoxy, hands down. System Three Cold Cure epoxy won't mind the lower temps at all.

https://mec.imgix.net/medias/sys_master/high-res/high-res/8818078187550/5001148-NOC00.jpg?w=600&h=600&auto=format&q=40&fit=fill&bg=0FFF (https://www.google.ca/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjqjJen693SAhUG82MKHfgBCDwQjRwIBw&url=https%3A%2F%2Fwww.mec.ca%2Fen%2Fproduct%2F5001-148%2FCold-Cure-Epoxy&psig=AFQjCNH7Fu5mvsNSdjIdmgzKsBf6fUb7hQ&ust=1489850361040216)

jackster
03-17-2017, 10:44 AM
...drew,
Not exactly sure where these laps occur.
A 15' boat should have full-length frames, solid or laminated.
Do they lap the keelson(hog)?
Do they lap the floors?
Do they bypass/lap corresponding pairs?
Yea, welcome aboard! :)

jpatrick
03-17-2017, 11:15 AM
I don't understand why you are "officially lost," when you say that the plans call for epoxy.

Jeff

Peerie Maa
03-17-2017, 11:34 AM
...drew,
Not exactly sure where these laps occur.
A 15' boat should have full-length frames, solid or laminated.
Do they lap the keelson(hog)?
Do they lap the floors?
Do they bypass/lap corresponding pairs?
Yea, welcome aboard! :)

Would a drift boat not be flat bottomed chine built, in which case the frames are three straight battens joined with half laps at the chines?
http://gregboats.com/pages/sixteen.gif

Centerpindrew
03-17-2017, 01:21 PM
I don't understand why you are "officially lost," when you say that the plans call for epoxy.

Jeff

Plans call for epoxy then states you can use polyurethane adhesives, ie: Elmers Ultimate, DAP, etc. as secondary glues...

Centerpindrew
03-17-2017, 01:23 PM
Peerie,

Ribs looks like the ones above in that boat..

Thorne
03-18-2017, 09:26 AM
Things will go much smoother if you post a link to the plans, photos will help also. Getting the terminology down can be a challenge for everyone, but as long as we're limited to text you'll have to work your way through it. As above, most plywood drift boats don't have laps, or are built lapstrake -- they have side panels that meet the bottom panel at the chine, often joined together with either a long narrow piece of solid wood (chine log) or an epoxy fillet.

I'd go for epoxy for all critical joints, and possibly use PL Premium construction adhesive for the less critical; as it cures by moisture rather than heat, and can be used in colder shops. Since we don't know the other materials or your hopes for the boat, we can't really say if epoxy is "worth it". If you're building a throw-away boat from construction ply, use PL Premium nearly everywhere. If you're building a nice boat with quality materials that will be stored indoors, I go for the higher cost of epoxy.

Peerie Maa
03-18-2017, 09:42 AM
Hello everyone,

I am a beginner at wooden boat building. My first boat I am going to build is a 15' wooden drift boat. On the plans it says to epoxy the ribs/frame lap joints but also shows fasteners in place as well (never removing them). So after reading over 1,000 posts on the internet, I am officially lost with what to use for a bonding agent at this point, ie: Epoxy, PL Premium, etc. Some say stick with epoxy and some say use a polyurethane..

I don’t have a problem spending the money on epoxy for this step but is it truly worth it for the rib framing lap joints? Again, they will be held in place with fasteners also and the inside of the boat won’t be exposed to constant water.

Not to mention that it’s still cool weather in Upstate NY and I am working in a cooler work shop, not 70 degrees!

Any information would be excellent! Thank you all.

Lapped frames, posted for the avoidance of confusion.

Set up next door, frames erected and fastened.

https://lh3.googleusercontent.com/1b_c7RY7OfYe7aRz8biSNdrRAa5PWs_ig3LlAnklSDJoAeKUDw KZTkZT1YWb15axyhz3VsiBnzsRSQ=w1024-h600-no

Centerpindrew
03-18-2017, 12:55 PM
Thank you all for the input.. I will be moving forward with epoxy on everything. I have no problem spending the money on it. I am building a boat from quality materials and want it to last.. Thanks again!