73 D18 roof replacement

[stanDman111]

strategy boards ?

[khantroll]

I think maybe "straight edgy" or straight-est?

[demon]

oops! yea i ment straitest boards and even these are not great. kinda bummed about it

[demon]

Got the driver side wall board installed! all covered in fiberglass resin so should last a life time. Looks great! The roof trusses or whatever you want to call them are another story. I bought 2x6s because they were the straightest pieces of wood they had and figured i could cut 2 out of each one. so thats what i did but after i cut them the bowed all different. the bottom side that needs to be straight bowes down. Thats not gona work !. Ive wetted them down and placed a piece of wood thru the center with parking stones on both ends to bow them .I would be ok if the headliner was bowed up a little but it cant hang down. Any advice ?? I should have just built all this out of metal. Im a metal fabricator so I wouldn't have had any prob but just figured I can just have fun and do this at home and it would be straightforward....Nope! the wood has been killing me!!

[stanDman111]

looks good = want to come do mine ? working with wood can be a pain & yes i was wondering if it would be easer to go with metal / easer to bow. but it is the retention  to the wall thats got me baffed?

[CapnDirk]

I would not force wood to do anything,  It may return to where it was.


My last roof joists.....


For each one, glued and clamped 2 1X3 (or 1X4) together of clear pine (or spruce) I get the pine at the local Lowes.


Cut to width needed and lay it down.


Tap a finish nail in 1/8 in and up from the bottom outside corner of assembly.


Mark centerline  on assembly.


Use a sufficiently wide (wider than the assembly) piece of soft flatbar about i/8 thick and 1 - 1 1/2 I used aluminum placed below the nails and draw upward at the centerline to the desired amount of rise and tap another nail in on the centerline.  You can now draw a clean arc with a pencil.


Cut with a jig saw and clean up with a sander.


If your ceiling AND roof are arced you would have to do it twice.


Seal them with your fiberglass resin before installing.  The first one can be used as the template for others.

[Rickf1985]

If you use 3/4" marine or exterior plywood and cut your rafter rough shapes out of that and then glue two together to get your 1 1/2" wide and then finish cut you will never have to worry about warped boards and you will have many times the strength of cut down lumber. It will also be much more water and rot resistant.

[TerryH]

If you use 3/4" marine or exterior plywood and cut your rafter rough shapes out of that and then glue two together to get your 1 1/2" wide and then finish cut you will never have to worry about warped boards and you will have many times the strength of cut down lumber. It will also be much more water and rot resistant.

I have to agree. 3/4" plywood is made of 6 layers of wood. First has the grain going ----, second goes |, third goes----, fourth goes | and so on. The structural strength increases with each grain direction change. Add to that, marine and exterior uses better glue between each layer. Also, marine supposedly has no voids in the core layer lay up.
Plywood or OSB is used in the web section of trusses for it's greater structural strength than lumber when used on edge. A truss's primary strength is achieved from the web.

[demon]

YOU GUYS ARE AWESOME! think ill just scrap the wood i cut for the trusses. I dont want it returning to what it was . I have plywood left over from the side panel that I can atleast give a try. But what you guys makes perfect sense. The only question I have is about screwing into the edge of the ply wood. Do you think that will be a problem?  Also I was thinking about how to make such a large radius perfect. I know thats not necessary but I knew there was a trick. I use aluminum and bow it all the time at the shop and have someone trace the arc while i hold it where i want but this doesnt produce an exact radius. obviously close enough and alot of the times im trying to make compound curves that are just purely esthetic. I found this video online of how to do it. super simple and makes a perfect arc . Kinda cool too!    https://www.youtube.com/watch?v=mYDABCzSRds

[CapnDirk]

I think he was trying to make a scallop more than a radius  .  In my method those veneers he had would have bee stood up.  I think you got that when you described what you do at the shop.


It's not a perfect radius, but you're probably only going to want about 3/4 inch rise (the idea being it's just there for water runoff).


One of my trusses was able to support my 200lbs suspended on cinder blocks.   As you can see the clear pine or spruce is not like the shelf stuff.

[demon]

I went to home depot again and looked at the wood they have there . They have that pine and its warped just as bad as damn near everything they have there. They have poplar that is really straight . I'd have to glue 2 pieces together but i think that would work. I have leftover plywood so ill at least give that a shot.

[CapnDirk]

Check Lowes if you have one.  Home Depot is closer to me, but they do not stock it.  Lowes does, at least in this area.  The poplar would be more expensive, but damn stout. 


Here is a pic down the length of an 8 foot 1x2 of the clear pine.  The 1x2 is what I'm using to build all the new bedroom cabinetry.  VERY straight.

[1990HR]

WOW, that is a lot of work!

[Rickf1985]

When I do my slide in I am going to draw the arc using a string and pin method but I plan to leave 16-18" across the top flat so that the A/C and all of the vents are on a flat surface. Being that it will be higher than the sides it will drain just fine.

[TerryH]

String and pin method works great. Wood boat builders have used it and variations for years. It can also be adapted to draw an ellipse should you need one. Also quite easy to do.

[demon]

what exactly is that?

[TerryH]

Using an arbitrary width of 90" for the truss and assuming plywood and assuming a 1" arc at center:
    - draw a line approx. 2" down along the 96" edge of the plywood.
    - mark the center point at 48".
    - based on 90", measure two points, one left and one right of center at   
45", 90 divided by 2.
    - place a pin or finishing nail at each of these points.
    - measure up 1" from the center point (1" arc) and place a pin there.
    - use a nail, clamp or something below the straight line as a tie off point for the string.
    - tie one end of the string to the clamp, route it around the left nail, over the center nail, back to and around the right nail and back to the clamp and tie off fairly taut.
    - remove the center nail.
    - take your pencil and using the inside of the string as a guide (fairly taut) trace an arc line above your straight line, left nail to right nail. This will give you a perfectly symmetrical arc.

It may sound more difficult than it actually is. I've done it for years with ease. If you want to practice, use some 2" painter's tape above the straight line for your pencil to see how it works. You could try on a piece of scrap wood first, whatever width you happen to have.
For speed and ease when making numerous pieces I would suggest making one template and tracing from it.

If you are interested in an ellipse, it is similar, but not identical.

If it helps I could draw something out for you.

[demon]

nope i totally get it! thanks
 

[Rickf1985]

You totally lost me W%    I forget the math off the top of my head but starting at the center top of the arc which is 2 1/2" in my case I draw a line straight down the center. Then I go to one side and come down to the 1" mark above the bottom of my rafter and do the same on the other side. Then I just had to do the calculation to figure out the bottom pin location and that calculation escapes me at this moment since I am very tired. A piece of string, a thumb tack and trial and error will work as good as math. Pick a spot on the center line that came down from the top mark and put your tack in and then hook your string to the tack and put a mark on the string at the left side marker and moved it in an arc towards the top. If it meets the top too high then raise your thumb tack and remark the string. Raising the tack will give you a tighter arc. You can go from either way. top to side or side to top, whatever feels more natural to you. Trial and error will get you there and like Terry said, you only need to actually measure one, use that one as a template to cut the rest. Remember, I am going to 2 1/2 because I am going to cut the top straight across so I have a flat top for 18".

[TerryH]

Sorry, I did this too quickly.

- based on 90", measure two points, one left and one right of center at   
45", 90 divided by 2.

actually it is 90" - 1" (arc) divided by 2 = 44 1/2.

[TerryH]

Certainly Rick's method will work for you as will CapnDirk's. I offered mine as I am a firm believer in the language of mathematics.
What works for you is what works for you.
Hopefully you will keep us informed of your progress.
This topic is of great interest to many.
Thank you, demon.
Hope I don't get struck by a thunder bolt for saying "thank you demon"! :)rotflmao :)rotflmao

[CapnDirk]

Rick has made a good point and I would not be surprised if it wasnt stock on some rigs.  A flat center section os say 18 inches (would have to accommodate the AC whatever that base gasket needs) and outer slightly straight sloping areas.  You would have to be careful that the break between the the flat center area and the outer slope didn't have a vent or something right there

[demon]

I made the curve on the last boards that im throwing away by welding a couple of pieces of aluminum flat bar together at and angle like he did in that video I posted but he used wood to do it . Im a metal fabricator so i have a lot of metal lying around so thats what i did. Its pretty much the same idea as using string the way you described.


I also have a 1995 Winnebago Brave and it has a curved roof. Its alot more curved than what im doing on the 73 and there are no flat spots for the ac or anything else up there. I don't think that the little amount of curve is even an issue at all.


My wife and son helped me cut strips from the rest of the plywood I have. My plan is to glue one of the nice really good pieces of plywood to one of the pieces I got from Lowes. The plywood has been lying on the ground in the showroom at my shop so its been out of the humidity and is pretty flat now anyway but wont be an issue as long as it stays strait when its standing up now. there will be boards ging between them any way. Thanks for the Great Idea ! I didnt think at all to use the plywood and I already had it! so far so good, it looks really strait. gonna get a router bit to trim the rest after i make the first one. that will save hours!!!


next question , should i glue them together with wood glue? any particular kind? or should I use the fiberglass resin?

[CapnDirk]

Resorcinol  MMMMMMmmmmm good!  Holds boats and planes together.


http://www.diy-wood-boat.com/Glue.html#PVA


I don't know if you stated, but how tall is the roof joist at its thickest point?  I'm curious as to how thick the ceiling is on those.

[demon]

Resorcinol  MMMMMMmmmmm good!  Holds boats and planes together.


http://www.diy-wood-boat.com/Glue.html#PVA


I don't know if you stated, but how tall is the roof joist at its thickest point?  I'm curious as to how thick the ceiling is on those.

well the original was flat and was 1 1/8" thick. mine will be 1 1/8 thick at the edges and 3/4 thicker in the middle ....well thats the plan. that way it has a curve for rain to run off. but i dont want a big curve across the top. I want it to look pretty stock. So in the middle of my roof it will be 1 7/8" thick