Help with boat construction

Hi this is my first post, but not my first time on this site.

I am building a 24' x 102" pleasure boat. I was going to build this boat out of wood, but due to wood rot in my previous boat. I decided to go with FRP.

I have built a male plug out of OSB & 2 layers of 2" strips of Luan. I have sanded the plug almost smooth.This plug is going to cast my female mold.

Please help me with my concerns:

Is it ok to fair with Drywall Mud or should I use a Body Filler? I read that Drywall Mud might shrink.

What type of primer should I use for my plug?

When do I prime the plug, before or after filler?

Should I paint the plug to see imperfections?

What is a typical layup for a female mold?

Thanks in advance.

 

There is a easyer way !Why do you want to make a female mould ??
If you simply build your boat over the top of what you already have then it will only increase in size by the thickness of the laminate you make the boat from . It can be faired and eventually painted and then taken off your wooden plug and then ground and sanded inside and then your frames can get bonded and so on !
Will save one pocket of money not to mention the time involved and you wont have a useless mould laying round for ever more !
Plaster mud is useless even if you paint over the top so dont think about it !!

 

I'll ditto Tunnels comments. Why would you want to build a boat shaped thing, three times before the hull can be seen?

Look up the several "one off" FRP methods. Since you have a male plug, why not just do as has been mentioned and laminate directly over what you have (cover with plastic sheeting). The inside doesn't need to be as fair as the outside anyway.

 

We used to get a sandblaster in and blast the ininside totally !
What sort of a lay up are you considering ?? Can peel ply the last csm layer and use it to sand and fair before you start filling Peel ply will give you a good idea of the surface shape as you are laying it ! Wet glass is asy to move round and put pressure on the highs and squash into the lows . Have only ever used 1 layer of 450 gram for this purpose .
Lets know wha you lay up will be !!

 

Intially I planned to use the "one off" FRP method.
Reasons for building female mold:
- I read somewhere that it is eaiser to make a mold than sand FRP.
- If I ever want to build another hull, I won't have to start from scratch.
- I believe that I would get a perfect finish, my worst fear is that my homemade boat looks homemade.

Fiberglass Layup for female mold.
Gelcoat
1.5 oz mat
1.5 oz mat
24 oz rw
1.5 oz mat
24 oz rw
1.5 oz mat
24 oz rw
1.5 oz mat
1.5 oz mat

Please correct me if you disagree. I am posting here because I do not have Boat Building experiance.

 

Making a mould !!
Fibre print through from the glass you are using is a major problem , Woven roving is one of the worst because of the course weave pattern so !!
Gel coat a generous thick coat but not to the point where it moves and starts to run . Let it go hard for 24 hours then a tissue and a generous wet coat of resin and ake the resin a bit faster than you will normally use , Again a 24 hour cure time then a 450 gram csm and hard the 2 x 45o gram csm . and build the csm with at least another 4 layers before introducing woven . Its a mould so woven is not really needed just csm .

I have just spent 8 weeks totally sanding a 46 foot hull mould that had terrible fibre print through from the heavy weight matt that was laid to close to the moulds surface .
The company was told it had to be resurfaced , but gently with fine wet and dry paper i have got it to a acceptable standard without going through the tooling gell into the fibres behind .

Use the recomended catalyst ratio for your Gel coat ( usually 1.5 % at 20C ) and need .7 of kg per m2 coverage rate or a little over .
Your first caot of resin Again check the ratio but 1.5% and use smaller brews and take you time dont get any air in the glass .
The best CSM is P matt !! a little more exspensive sometimes but wets better that E matt 450gram is easy to work with for you layers . Once you get away from the moulds surface then you can lay 3 layers in one hit . . Heat build up you dont want !! Heat means shrinkage !!!!!shrinkage means distortion .
The time for the first layers to cure is important again it fibre trint through you are trying to prevent . If you are ablbe at he very end before any bracing get places and glassed on the new mould tent the whole thing and cook it at about 25 C or 30C for 24 hours . Makes the riesin much more stable and on the whole a better lasting mould same with the boat when you get to make one the 24 hour cure stabilises and hardens the resin better .

Have fun !!
.

 

Would you support the mold with pipe or could I use wood cradles?

 

Steel frame and only lightly glass !! If you use great heaps of glass it pulls over time specially if the mould goes outside and sits in the sun .
Keep the steel away from the mould nothing touching any where . Good idea is to have a 100 mm wide flang round the top , helps tp hold the mould shape and when you glass the hull take the glass up and over . As you build the hull eventually it will come loose in the mould (demould ) and want to pull away hence changes the shape of the hull and gets worse as the build takes place , with glass over the flange you can clamp the two together .Have yu sorted the flange detail for the deck join ?? A simple rolled ver edge is good to put the deck onto and glass the gunwhale totally inside Usng doublebias 150 mm wide tape , two layers with csm under and over !
:idea:Depending on the flang belting/rubbing strip that you want to use you can simply cut flush and screw through unto the glass join or leave a part of the glass flange stikng out and push over or what ever . Something to take into consideration Now!!! so see whats availible and whats best for your situation . Get a foot long sample and build the hull /deck edge to suit so everything fits properly . Make sure its readerly availible and in the color you want . Vetus have a good range of shapes and colors .

 

Thanks, I did not think of the glass coming loose from the mold. The reason I wanted to use wood for the supports for the mold is that I don't have any welding experience, but this seems like a good time to learn.

I am going to take your advise and get a sample of the rub rail. I am going to take all of your advise. Evidently you know what going on. I really appreciate all of your help.

 

25 mm water pipe and use 8 mm reinforcing steel and bend in a zigg zagg and just hire some one o tack weld it all . You can do 90 % of the work . Stands dont really need stands . we are not moving our moulds but have a frame over the mould and work off that . Cuts down on the demoulding and distortion thing , It will happen but no where as much ! First time had to build 8 racing yachts and a very hi degree of accuracy so couldnt afford any distortion .just used scafolding and some planks Suspendd and not touching any where till we were halfway through the build and then dismantled and worked on top of the laminate that was in the boat . Never had one problem !and was as fair as when they came out .
Tell me about the place where you are building and weather etc etc !
Do you have a laminate worked out for the hull ??
wHAT KIND OF GLASS YOU USING ??
iNBOARD OR OUT BOARD ?
FAST OR SLOW ??
wHATS THE HULL SHAPE LIKE ??:?:

 

I am located in South Louisiana, U.S.. The weather is hot and hummid with short winters. So during the summer my family loves to be on the water. We love watersports so I decided to build a wakeboard boat.

The hull is V shaped (see my profile pic). I will install a 5.7L PCM engine with trans & V-drive. This boat should top out aprox. 45mph. My biggest concern is the layup schedule. I have not bought any fiberglass materials yet, so any suggestions would be appreciated. Weight is not an issue.

 

A mono with a semi pickle forked bow . Id fit a flange right round the edge of the thing and will help for sure to keep the hull in shape once you have taken it out of or off the mould .

Ok weather during the glassing stage !!
Humidity could be something worth considering . The moisture can do starnge things to you glassing . Moisture slows resin and in exstreme situations the laminate never really goes completely hard .
Moisture is in the air and the glass hold this so you need to keep all your glass dry as . A dehumidifyer is a good way to keep t dry or a small room with a heater . But the sounds like you have you share of nice wether so the humidifyer would be my choice . Lay plasitc and stack the glass rolls on top and tent it ! seal simply by folds so you can get into it when you need glass . The smaller the amount of air space the easyer and quicker it works .
Moisture come up from the floor as well be it wood or concrete including walls and any surface thats not covered with plastic .

READ UP AND GET FAMILIAR WITH THE GLASSING PROCEDURE WAY AHEAD OF TIME SO ITS STUCK IN YOUR MIND .
iTS SIMPLE IF YOU STICK TO THE BASICS LISTEN TO ADVISE GIVEN AND MAKE YOU YOUR OWN MIND IF ITS GOOD ADVISE OR NOT .
i SPEND MY LIFE TRAVELING TO ASIAN COUNTRIES SHOWING BETTER WAYS TO WORK AND MAKE LIFE BETTER . EACH COUNTRY IVE BEEN HAS IT OWN SET OF FUNNY LITTLE THINGS THAT AFFECT GLASSING AND THE TEMPRATURE RANGE FROM REALLY HOT TO MINUS 20c SO THAT A WHOLE DIFFERANT BALL GAME DEALLING WITH EXSTREMES .
GOOD LUCK AND KEEP POSTNG !!

 

Just got finished jacking up my plug so I can construct a flange in the morning "my Friday off". What else would I do with free time.