Red Oak for Roof Spars

[eamarquardt]

I've seen the Kuffle Creek plans and some of the things they suggest are "the hard way". I have "talked" with Halfdome Danny and the interior roof with all the little blocks is not the way "a cabinet maker" would do it. He uses a router to rabbit a notch for the beams and interior ceiling skin. Then the outer skin goes on. Seems like a lot easier (once you make a jig for your router so it doesn't tip).

As far as beams go. I don't think it matters what they are made of. If you have an interior skin and an exterior skin (say of 1/8 ply of good quality) the strenght of the beams will really be secondary to that of the skins if they are held firmly attached to the beams. On the edges of hollow core doors they use pine or sometimes particle board as you need to attach locks and hinges) but the rest of the skins are separated by a cardboard matrix. As long as the skins are held in position by the the internal supports, the skins will provide plenty of ridgidity. Just try and bend a hollow core door with cardboard holding the skins apart (although I wouldn't recommend using cardboard in a teardrop). I plan on using the parts of the 5X5 plywood that I don't need (as I'll be trimming them to 4 feet for the sides). Glue a couple pieces together, rip to desired width, and you have good beams/ribs and don't have to buy any wood. The more ribs the merrier but I don't see that they need to be more than an inch wide. The key is fastening the interior and exterior skins to the beams. Additionally, the curvature (if you don't have straight sections) of the cabin roof will add rigidity to the structure.

If there is something wrong with this plan, please "speak now or forever hold your peace". I'm certainly open to input.

Cheers,

Gus

[dh]

Hey Gus, won't you be putting fasteners into the endgrain of plywood when you attach walls and spars together? Also, I didn't mean to inply perfectly straight red oak was available at the BORG, but, for stated purpus, pretty straight 1x2 R O can be had when compared to 1x2 poplar, at least at my local Lowes.

[bobhenry]

I used yellow pine for roof spars,

Southern yellow pine is 50% stronger than spruce pine fir grade.

A #1 grade 2x10 or 2x12 will rip nicely into 2x2's (1 1/2" x 1 1/2"). At slight less than $1.00 a foot you can net 7 cuts out of a 2x12. These 7 five foot spars will cost you about 70 cents a piece.

When ripping cut a few extra because 1 or 2 may go wild with grain release and curl a bit. Let them set 48 hours if possible and use the best. Any with a slight bow use with the crown up.

I set mine in a notch in the sidewall and attach with a lot of glue and a 3" construction screw thru the side wall into the spar at an upward angle to go somewhat across the grain in the 2x2.






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Simpson makes a hanger that will work for this application also !

face mount

top mount

[planovet]

Also, I didn't mean to imply perfectly straight red oak was available at the BORG

I know that. All I was saying was that my BORG had some pretty crappy red oak. Yours might have had better.

All I was saying is that don't think you are going to get straight pieces just because it's red oak.

[aggie79]

Gus brings up some good points.

As far as beams go. I don't think it matters what they are made of. If you have an interior skin and an exterior skin (say of 1/8 ply of good quality) the strenght of the beams will really be secondary to that of the skins if they are held firmly attached to the beams. As long as the skins are held in position by the the internal supports, the skins will provide plenty of ridgidity.

Even though I used poplar for the spars, it really doesn't matter what you use if it is wide enough to glue/fasten the roof and ceiling skins.

I've seen the Kuffle Creek plans and some of the things they suggest are "the hard way". I have "talked" with Halfdome Danny and the interior roof with all the little blocks is not the way "a cabinet maker" would do it. He uses a router to rabbit a notch for the beams and interior ceiling skin. Then the outer skin goes on. Seems like a lot easier (once you make a jig for your router so it doesn't tip).

There are many ways frame and skin the roof and ceiling. Steve Frederick's method creates a ledge for the ceiling skin and spars. I did something a little different by making removable roof framing using spars and a "rib" on each side. This allowed me to skin the inside of the ceiling (and apply hull liner) with the framing on the bench rather than working overhead inside the teardrop.

Here is a picture of the roof framing (upside down. The diagonal strips are temporary to keep things square.)



This shows the inside ceiling plywood being installed.



And this picture shows the hull liner installed.

[Noah_and_Tina]

Wow, that was a heck of a lot more information than I expected overnight

It sounds like I'll probably stick with pine. I'm not a huge fan of ripping lumber as I'm just not that comfortable with my table saw (this is my first wood working project since high school wood shop). I'll look and see if they have enough reasonable quality furring strips. If not, I'll just have to man up and start ripping some 2x12s.

[eamarquardt]

Hey Gus, won't you be putting fasteners into the endgrain of plywood when you attach walls and spars together?

Nope. I plan on a 3/8" ply exterior wall, 1" internal structure/insulation and a 1/8" interior skin. There will be a rabbet (a little deeper than the 1" insulation and the interior skin) into the 1" structure and 1/8" interior skin to form a ledge where the interior roof skin and ribs will fit. After installing the interior skin I'll fill in the spaces inbetween the ribs (the rabbeted area) to bring it flush with the exterior 3/8' ply. The wall structure will be all glued together. I'll probably glue the ribs/beams to the interior skin before putting it in place. I figure that stapling and gluing the interior skin to this 1 1/8 inch rabbet and the exterior skin to the 1 1/2 top edge will be plenty strong. I'll build up the space between ribs to provide a 1 1/2 top edge (3/8 exterior ply, the 1" internal structure, and 1/8" interior skin) and the exterior skin will be stapled and glued in place. A vertical screw, through the rib into the 1" structure of the wall, will keep it in place but I don't think it will contribute much to the strenght of the structure. I really think the curved skins being securely attached to sides, the skins being securely fastend to the ribs (glue on inside, glue and staples on top) will be more than sufficient. The purpose of the ribs is just to keep the interior skin connected to the exterior skin to provide an integrated stucture. This will proved a nice clean interior wall to ceiling joint that will not require any trim. I got the rabbet idea from Halfdome Danny.

Whatdayathink?

Unfortunately construction is delayed as #2 son's Subaru to VW "heart and lung" transplant and building him a flatbed to carry the finished 130 HP (up from 50 odd HP) Baja Bugnand a couple of bikes around is distracting me.

Cheers

Gus

[eamarquardt]

I did something a little different by making removable roof framing using spars and a "rib" on each side. This allowed me to skin the inside of the ceiling (and apply hull liner) with the framing on the bench rather than working overhead inside the teardrop.

Another clever way to accomplish the task! I'd say "more than one way to skin a cat", but I've gotten in "trouble" for saying that in the past so I won't say that again.

Cheers,

Gus

[Larry C]

Gus brings up some good points.

As far as beams go. I don't think it matters what they are made of. If you have an interior skin and an exterior skin (say of 1/8 ply of good quality) the strenght of the beams will really be secondary to that of the skins if they are held firmly attached to the beams. As long as the skins are held in position by the the internal supports, the skins will provide plenty of ridgidity.

Even though I used poplar for the spars, it really doesn't matter what you use if it is wide enough to glue/fasten the roof and ceiling skins.

I've seen the Kuffle Creek plans and some of the things they suggest are "the hard way". I have "talked" with Halfdome Danny and the interior roof with all the little blocks is not the way "a cabinet maker" would do it. He uses a router to rabbit a notch for the beams and interior ceiling skin. Then the outer skin goes on. Seems like a lot easier (once you make a jig for your router so it doesn't tip).

There are many ways frame and skin the roof and ceiling. Steve Frederick's method creates a ledge for the ceiling skin and spars. I did something a little different by making removable roof framing using spars and a "rib" on each side. This allowed me to skin the inside of the ceiling (and apply hull liner) with the framing on the bench rather than working overhead inside the teardrop.

Here is a picture of the roof framing (upside down. The diagonal strips are temporary to keep things square.)



This shows the inside ceiling plywood being installed.



And this picture shows the hull liner installed.

Aggie79,
I too have been trying to find a good method for attaching spars and inner skins. I like Steve Fredricks method, but incorporating it into my laminated perimiter won't work. I don't quite get Half Dome Danny's method, but my perimeter laminations are only 1.5"deep so I don't see how a rabbet would work for my 1.5" spars. Maybe I just can't picture it.

However, your method looks like it could work for my build, especially for my basement construction, as I want to build a modular (mostly finished) unit that can be quickly assembled in my garage.

It looks like your side ribs are narrow ( maybe 1/2" X 1.5" wide) plywood. Did you have any problem with spring back when you attached the skins? I have a 5' span and wonder if just 2 narrow strips of play will hold it's shape??

I suppose I could make 2-3 separate shorter panels with shorter ribs to help prevent spring back.

Here's the profile I need to follow:

[eamarquardt]

I too have been trying to find a good method for attaching spars and inner skins. I like Steve Fredricks method, but incorporating it into my laminated perimiter won't work. I don't quite get Half Dome Danny's method, but my perimeter laminations are only 1.5"deep so I don't see how a rabbet would work for my 1.5" spars. Maybe I just can't picture it.

Lottsa good ideas flowing!

Larry C, I like your perimeter laminations.
1) What did you use as far as wood and glue?
2) What is the height (when the wall is upright so we're clear) of your laminations and the thickness (in the horizontal direction when the wall is upright?
3) What are you planning to use for the the exterior skin and are you going to have an interior skin?
4) I think Danny's method might work for you depending on the dimensions of your laminations.

Gotta help #2 son with his Baja Bug radiatory right now but if you post the dimensions of your laminations, later I'll make a sketch or two and post them so you can see how it works.

Cheers,

Gus

[Larry C]

I too have been trying to find a good method for attaching spars and inner skins. I like Steve Fredricks method, but incorporating it into my laminated perimiter won't work. I don't quite get Half Dome Danny's method, but my perimeter laminations are only 1.5"deep so I don't see how a rabbet would work for my 1.5" spars. Maybe I just can't picture it.

Lottsa good ideas flowing!

Larry C, I like your perimeter laminations.
1) What did you use as far as wood and glue?
2) What is the height (when the wall is upright so we're clear) of your laminations and the thickness (in the horizontal direction when the wall is upright?
3) What are you planning to use for the the exterior skin and are you going to have an interior skin?
4) I think Danny's method might work for you depending on the dimensions of your laminations.

Gotta help #2 son with his Baja Bug radiatory right now but if you post the dimensions of your laminations, later I'll make a sketch or two and post them so you can see how it works.

Cheers,

Gus

Gus,

The photo is a little unclear. Both side laminations are stacked in this photo.

1) The wood laminatios are Basswood and pine, 1/8" X 13/16", Glue was Titebond 3. After glue-up I surface planed to 3/4", virtually no spring backback using glued laminations.

2)The dimensions are 3/4" (horz.) X 1-1/2" (vert.) with walls standing.

3)Exterior skin will be 1/8" thick X 3/4" wide wood strips(various species). W/ fiberglass cloth on outside and inside of exterior wall. Interior wall will be 1/8" BB plywood.

The sandwich panel will be completed with interior framing & foam insulation. Similar to my floor construction, see image below:

4) Total wall thickness 1"-1-1/8" depending on fiberglass/epoxy thickness.

my spars are 5/8" X 1-1/2" PT Southern Yellow Pine

[aggie79]

Aggie79,
I too have been trying to find a good method for attaching spars and inner skins. I like Steve Fredricks method, but incorporating it into my laminated perimiter won't work. I don't quite get Half Dome Danny's method, but my perimeter laminations are only 1.5"deep so I don't see how a rabbet would work for my 1.5" spars. Maybe I just can't picture it.

However, your method looks like it could work for my build, especially for my basement construction, as I want to build a modular (mostly finished) unit that can be quickly assembled in my garage.

It looks like your side ribs are narrow ( maybe 1/2" X 1.5" wide) plywood. Did you have any problem with spring back when you attached the skins? I have a 5' span and wonder if just 2 narrow strips of play will hold it's shape??

I suppose I could make 2-3 separate shorter panels with shorter ribs to help prevent spring back.

Here's the profile I need to follow:

Larry,

Your perimeter laminations are a work of art! And I love your teardrop profile.

My teardrop has a front cabinet. The roof framing started at the top of the cabinet and ran back to the bulkhead wall. The front was framed in a separate assembly. So I would say it can be done in multiple pieces.

I don't have the woodworking skills that you do, so I had to frame the roof assembly in place to be sure everything fits. First I clamped the side "ribs" or plates in place. (They were cut from 3/4" plywood and are 1 1/2" deep.) Then I cut the spars and fitted them with two pocket screws and glue - PL Premium.





I used 1/8" Russian Birch plywood for the ceiling skin. It really did not cause any springback. With only the ceiling plywood on and not the exterior roof plywood on, the assembly will flex enough to refit it in place.



Once I had everything aligned, I pre-drilled pilot holes for screws that would fasten from the inside of the "ribs" into the plywood frame of the sidewall. I then removed the assembly, added a bead of PL Premium at both ribs, fit the assembly back in place, and fastened with screws. I then came back and removed the top pocket screw at each spar. Then I drilled pilot holes in that location from the outside of the teadrop into the spars. Then screws were fastened from the outside, through the plywood frame, plywood rib, and into each spar.

[Larry C]

Your perimeter laminations are a work of art! And I love your teardrop profile.

My teardrop has a front cabinet. The roof framing started at the top of the cabinet and ran back to the bulkhead wall. The front was framed in a separate assembly. So I would say it can be done in multiple pieces.

I don't have the woodworking skills that you do, so I had to frame the roof assembly in place to be sure everything fits. First I clamped the side "ribs" or plates in place. (They were cut from 3/4" plywood and are 1 1/2" deep.) Then I cut the spars and fitted them with two pocket screws and glue - PL Premium.





I used 1/8" Russian Birch plywood for the ceiling skin. It really did not cause any springback. With only the ceiling plywood on and not the exterior roof plywood on, the assembly will flex enough to refit it in place.



Once I had everything aligned, I pre-drilled pilot holes for screws that would fasten from the inside of the "ribs" into the plywood frame of the sidewall. I then removed the assembly, added a bead of PL Premium at both ribs, fit the assembly back in place, and fastened with screws. I then came back and removed the top pocket screw at each spar. Then I drilled pilot holes in that location from the outside of the teadrop into the spars. Then screws were fastened from the outside, through the plywood frame, plywood rib, and into each spar.[/quote]

Tom,
My perimeter laminations are just the method copied from Mike's Ultralight plan. The profile shape is also Mike's Ultralight. The lamination method is really easy to do.
I think your method of building the spars and inner skin on a bench makes a lot of sense. It's like building a series of hatches. My Russian Birch is 5X5 so maybe making them in 5' panels will work best. I could just make more perimeter laminations for the ribs instead of using plywood.
I really don't have much in the way of woodworking skills. I build boats that have curves, no right angles. I am not the cabinet maker you are. I spend a lot of time stealing ideas from you and others.
Thanks for clear details, it helps a lot.

[eamarquardt]

Here is a sketch (forgive my rough drawings) of the "plan".



I think Larry could make it work with his current side laminations but it would be a bit tight. You laminate the walls up and then do the rabbeting.

Hope this helps.

Cheers,

Gus

[planovet]

Here is a sketch (forgive my rough drawings) of the "plan".

That's pretty much how it is in Steve's shop notes. And that's the way I built mine. It's very easy to lay in the ceiling, then the spars and then the roof. I screwed my spars down into the wall framing because my sides were already finished. Ended up very solid.

Worked very well for me.

Would be more difficult to do with the laminated frame though.