lilmurray
Member
Sorry to be AWOL for a couple days but sometimes life intrudes.
You could call this post a follow up on the fine work done by bhyde and others very early on in this thread. (Pgs 1-2).
Bhydes photos show the ‘yacht’ under construction. Since they were taken I have noticed that there has been much discussion of the materials used and speculation about whether additional structural reinforcement was added since bhyde’s pictures were posted. If you have these sorts of questions concerning the construction of the cabin my previously posted interior photos should help answer them. I do have a few more interior shots here with some discussion. These were all taken below deck inside the port hull a few days before “Flyin” went in the water. As has been my approach from the beginning I will not be offering my opinion on what these photos show. I will however, offer some help and information that all of you might find usefull in forming your own opinion.
Here we are looking forward from a little ahead of amidship. Nothing much has changed since bhyde made his photos. Note, that construction is plywood over 1x2 battens with 2x4 "frames". The "frames" are positioned at approximately 4' on center. The assembled group of 2x4s at the center reinforce the vertical bow stem. The white squares with the grey dots in the top third of the frame are the terminations of the 2x4 members that support the bridge deck and join the hulls together. We will have a closer look at these and some other details below. BTW peeking out from the bilge forward is a plastic 20-30 gallon drum. I was told that several of these were going to be converted to "tanks" to serve various purposes on the boat. Some were said to be food grade and would hold fresh water.
I rotated slightly toward the port side to capture this area in a little more detail. This is the area of the hull that turns inward toward the bow. Note that the "frams do not follow the angle of the bow. Rather the 4" dimension of the lumber is perpendicular to the fore and aft center line of the boat. Rather than bevel the short edge of the 2x4 or even the bottoms of the notches for the stringers 2 screws are driven into the bottom of the slots with their heads exposed to "support" the stringer. Notice also that the fore and aft seams in the plywood are intermittently backed up by small rectangles of plywood. Apparently this was done to support the butt seams while the fiberglass tape was applied. Although I cannot say for certain that the only fiberglass reinforcement applied to the exterior of the hulls was done in the form of 5-6" wide tape it appears to me that this was indeed the case.
Now let's look closely at the lower right corner of this picture. For clarity I have also rotated the image and sharpened it. There has been quite a bit of discussion in this thread about the materials used on this craft. Several sources, including Hot Rod himself have indicated that the hulls were made from 1/2 material. This is not the case. I captured many images of grade and specification marks and this one down near the waterline clearly indicates that the plywood used is 3/8" C-D sheathing grade plywood, commonly referred to in the US building trade as CDX. Every other plywood grading mark I captured in the hull sections is consistent with this. This material allows for considerable knots and voids. 3/8 panels are structurally span rated at 24-0. That means they are span rated against the grain at 20 inches and with the grain at 0 inches. C-D grade sheathing contains significant knots and voids, and is rated at Exposure 1. Exposure 1 panels are not "exterior glue" per se. The glue used in these panels is designed to withstand some wetness and dampness encountered during the construction process but is not rated for long term exposure to the elements. If you would like the definitive word on what 3/8 C-D sheathing plywood is rated to do have a look here: http://www.plumcreek.com/Portals/0/downloads/productInfo/J20.pdf.
Now we are looking at one of the support beam attachment points. These span the the distance between the inner surfaces of the hulls and provide the main structural support for the bridge deck. The beams themselves are made up of multiple 2x4 sections epoxied together in the fashion described by Hot Rod as "steel reinforced beams". I talked about this earlier in the context of the cabin, but essentially these are between 3 to 5 thicknesses of 2x4 glued together with epoxy paste and "reinforced" by galvanized builder's screws on about 6" centers. In this application the outer 2x4s pass into the hull on either side of the vertical "frame" while the middle thickness butts into the hull. The whole assembly is joined with a 1/2 galvanized carriage bolt through with nuts and washers on both sides. There has been some comment here about these bolts. (Some posters are calling them "coach bolts". I guess this is a British or Colonial idiom. I LIKE IT!) I won't comment on the precise strength of these bolts but I will point out two things. First, Hot Rod has installed them with washers on the head side, presumably to limit pull through. This point loads the little shoulders on the heads of these bolts. With stress and movement the square shoulders will either shear away or dig in to washer leaving the nuts to become loose. More importantly, my guess is that they are significantly stronger than the wood assembly that the hold together.
Notice also that there is a grade mark visible on the 2x4 "frame" indicating " KD Hem-Fir STUD". This is typical of all the lumber I have seen on the "Flyin". KD means kiln dried, Hem-FIr is the species group composed of Western Hemlock and various true fir species. Non-appearance grade lumber is grouped together by species with roughly equivalent structural properties. BTW this is not the superior Douglas Fir Lumber that many people know. STUD is the structural grade and speaks to the number of knots and the percentage of heartwood (the strong stuff) in the graded piece. "STUD" is roughly equivalent to grade #3. Most houses are spec'ed and built at #2 or better for vertical and floor members and #1 or SEL (Select Structural) for beams and critical load bearing components. At one point I wrote a long description of exactly what these designations mean but somehow I lost it in the computer universe. Very briefly let me say that STUD grade lumber does not meet the requirements for most common building construction applications. Most carpenters consider it "hobby wood" and would not use it even in the limited applications where it is acceptable because the KD process makes the wood very prone to cracking and splitting when it is fastened. I observed many conditions (more in the cabin than the hulls.) where the builders screws used split and cracked the wood.
More information on how construction lumber is graded can be found here: http://www.engr.sjsu.edu/dmerrick/164/WWPA_PUM.pdf.
Here are three more views of inside the inner wall of the port hull. If you recall this is a pretty much an uninterrupted vertical surface fore to aft except for the small 90 x90 degree chine not far above the waterline. You get a very good look at how it is constructed here. Notice also the common romex wire used here. I will have more to say on this later.
Finally this is a view looking toward the aft port quarter showing the framing for the transom steps.
Next post will deal with some of the "ships systems".
You could call this post a follow up on the fine work done by bhyde and others very early on in this thread. (Pgs 1-2).
Bhydes photos show the ‘yacht’ under construction. Since they were taken I have noticed that there has been much discussion of the materials used and speculation about whether additional structural reinforcement was added since bhyde’s pictures were posted. If you have these sorts of questions concerning the construction of the cabin my previously posted interior photos should help answer them. I do have a few more interior shots here with some discussion. These were all taken below deck inside the port hull a few days before “Flyin” went in the water. As has been my approach from the beginning I will not be offering my opinion on what these photos show. I will however, offer some help and information that all of you might find usefull in forming your own opinion.
Here we are looking forward from a little ahead of amidship. Nothing much has changed since bhyde made his photos. Note, that construction is plywood over 1x2 battens with 2x4 "frames". The "frames" are positioned at approximately 4' on center. The assembled group of 2x4s at the center reinforce the vertical bow stem. The white squares with the grey dots in the top third of the frame are the terminations of the 2x4 members that support the bridge deck and join the hulls together. We will have a closer look at these and some other details below. BTW peeking out from the bilge forward is a plastic 20-30 gallon drum. I was told that several of these were going to be converted to "tanks" to serve various purposes on the boat. Some were said to be food grade and would hold fresh water.
I rotated slightly toward the port side to capture this area in a little more detail. This is the area of the hull that turns inward toward the bow. Note that the "frams do not follow the angle of the bow. Rather the 4" dimension of the lumber is perpendicular to the fore and aft center line of the boat. Rather than bevel the short edge of the 2x4 or even the bottoms of the notches for the stringers 2 screws are driven into the bottom of the slots with their heads exposed to "support" the stringer. Notice also that the fore and aft seams in the plywood are intermittently backed up by small rectangles of plywood. Apparently this was done to support the butt seams while the fiberglass tape was applied. Although I cannot say for certain that the only fiberglass reinforcement applied to the exterior of the hulls was done in the form of 5-6" wide tape it appears to me that this was indeed the case.
Now let's look closely at the lower right corner of this picture. For clarity I have also rotated the image and sharpened it. There has been quite a bit of discussion in this thread about the materials used on this craft. Several sources, including Hot Rod himself have indicated that the hulls were made from 1/2 material. This is not the case. I captured many images of grade and specification marks and this one down near the waterline clearly indicates that the plywood used is 3/8" C-D sheathing grade plywood, commonly referred to in the US building trade as CDX. Every other plywood grading mark I captured in the hull sections is consistent with this. This material allows for considerable knots and voids. 3/8 panels are structurally span rated at 24-0. That means they are span rated against the grain at 20 inches and with the grain at 0 inches. C-D grade sheathing contains significant knots and voids, and is rated at Exposure 1. Exposure 1 panels are not "exterior glue" per se. The glue used in these panels is designed to withstand some wetness and dampness encountered during the construction process but is not rated for long term exposure to the elements. If you would like the definitive word on what 3/8 C-D sheathing plywood is rated to do have a look here: http://www.plumcreek.com/Portals/0/downloads/productInfo/J20.pdf.
Now we are looking at one of the support beam attachment points. These span the the distance between the inner surfaces of the hulls and provide the main structural support for the bridge deck. The beams themselves are made up of multiple 2x4 sections epoxied together in the fashion described by Hot Rod as "steel reinforced beams". I talked about this earlier in the context of the cabin, but essentially these are between 3 to 5 thicknesses of 2x4 glued together with epoxy paste and "reinforced" by galvanized builder's screws on about 6" centers. In this application the outer 2x4s pass into the hull on either side of the vertical "frame" while the middle thickness butts into the hull. The whole assembly is joined with a 1/2 galvanized carriage bolt through with nuts and washers on both sides. There has been some comment here about these bolts. (Some posters are calling them "coach bolts". I guess this is a British or Colonial idiom. I LIKE IT!) I won't comment on the precise strength of these bolts but I will point out two things. First, Hot Rod has installed them with washers on the head side, presumably to limit pull through. This point loads the little shoulders on the heads of these bolts. With stress and movement the square shoulders will either shear away or dig in to washer leaving the nuts to become loose. More importantly, my guess is that they are significantly stronger than the wood assembly that the hold together.
Notice also that there is a grade mark visible on the 2x4 "frame" indicating " KD Hem-Fir STUD". This is typical of all the lumber I have seen on the "Flyin". KD means kiln dried, Hem-FIr is the species group composed of Western Hemlock and various true fir species. Non-appearance grade lumber is grouped together by species with roughly equivalent structural properties. BTW this is not the superior Douglas Fir Lumber that many people know. STUD is the structural grade and speaks to the number of knots and the percentage of heartwood (the strong stuff) in the graded piece. "STUD" is roughly equivalent to grade #3. Most houses are spec'ed and built at #2 or better for vertical and floor members and #1 or SEL (Select Structural) for beams and critical load bearing components. At one point I wrote a long description of exactly what these designations mean but somehow I lost it in the computer universe. Very briefly let me say that STUD grade lumber does not meet the requirements for most common building construction applications. Most carpenters consider it "hobby wood" and would not use it even in the limited applications where it is acceptable because the KD process makes the wood very prone to cracking and splitting when it is fastened. I observed many conditions (more in the cabin than the hulls.) where the builders screws used split and cracked the wood.
More information on how construction lumber is graded can be found here: http://www.engr.sjsu.edu/dmerrick/164/WWPA_PUM.pdf.
Here are three more views of inside the inner wall of the port hull. If you recall this is a pretty much an uninterrupted vertical surface fore to aft except for the small 90 x90 degree chine not far above the waterline. You get a very good look at how it is constructed here. Notice also the common romex wire used here. I will have more to say on this later.
Finally this is a view looking toward the aft port quarter showing the framing for the transom steps.
Next post will deal with some of the "ships systems".
