Master Marine 28' stringer question

[doug42190]

This weekend's efforts: I ground and prepped the outside edge of the port inner stringer to be filleted and tabbed. I did put a nice fillet on it and three layers of DB 1200 -- I was out of the 12 oz 6" tape so I cut 5" strips off of my roll of DB1200. I also ground and prepped the side and chine joint on the port side, layed in a nice fillet and covered it with 1 layer of DB 1200 -- 5" strip. The joint where the side and chine comes together is a very sharp angle. This picture gives a fairly good look at the sharpness of that joint.



Since I removed so much loose roving during the destruct phase, I am putting back 2 layers of 1708 and 2 layers of 1808 but I need to cover the chine and go up the wall about 6" to replace what I took out. That seemed about the right amount of glass to get the stiffness back in the hull between the inner stringers (actually I used 2-1708, 1-1808, and 2-DB1700 in there). Now I am going to lay the glass from the stringer to the chine/side -- then come back and install the outer stringers at another time.

This presents an opportunity for a structural question; I am removing the inner liner and just going back with the deck to the sides. I understand that the support provided by the liner must be replaced. Originally the hull had three bulkheads and no frames. I will have 4 bulkheads (the fourth being a full bulkhead at the rear of the anchor locker) and it will have 4 frames per side. If I take these layers I am about to put in the hull (and over to the chine) -- if I take them staggered (5" each) up the hull side to just below the gunnel cap (2 layers of 1708 and 2 layers of 1808) will that be sufficient to replace the structural loss of removing the liner?

Pictures will be uploaded as soon as my wife gets back and tells me where the cable is for the camera

Thanks for any comments or feedback.
Doug

[tech_support]

Im real sorry, but I read this four times and Im still not sure I 100% understand what your talking about

I will have 4 bulkheads (the fourth being a full bulkhead at the rear of the anchor locker) and it will have 4 frames per side.

So are you going to have 4 bulkhead AND four floor frames? Maybe its just the nomenclature Floor frame is a transverse support that generally ends under the sole, and extends up the sides of the hull. Bulk head is the same, but its more or less full width. 4 bulkheads and 4 frames means 8 transverse stiffeners.

If I take these layers I am about to put in the hull (and over to the chine) -- if I take them staggered (5" each) up the hull side to just below the gunnel cap (2 layers of 1708 and 2 layers of 1808) will that be sufficient to replace the structural loss of removing the liner?

Do you mean the extra glass you are putting into the bottom of the hull for stiffness? If so, yes yo uneed to overlap up the side at the chine joint. No, it does not replace any/much stiffness

Glassing the new sole to the sides IS going to add a lot of stiffness. Depending on how big the span between the top od the new sole and the hull/deck joint, you might need a hull side stiffener. This can be you frames, or a longitudinal stiffener, or both. How was the liner bonded to the hull side (or was it bonded to the hullside?) Trying to determine what they had in the original design to stiffen the hull side. How about a picture of the demo when you ripped out the liner, that might help me

[doug42190]

Shine,
Likely it is my misuse of the correct terms. The bulkheads only went from inner stringer to inner stringer in the original build. The new four bulkheads will be (bow to stern) one at the anchor locker that goes side to side and bilge to top side; the next one will be for a storage compartment (about 6 feet from the anchor locker); then back four feet to the forward end of the gas tank compartment; then about 9 feet to the rear of the gas tank compartment. Except for the anchor locker, this was the original configuration.





Originally, from inner stringer to outer stringer and beyond to the sides, there was no structure in there at all. What I called frames were extra bracing/bulkheads between the sides and outer stringer and the outer and inner stringer -- to give extra support to the sole (with cleats on top) and more rigidity overall to the hull.

Here you can see what I called a frame -- the bulkhead is still at the back of the gas tank in this picture.



In the original hull configuration the area between the inner and outer stringers and outer stringers and hull sides were filled with foam. This foam also went up the sides between the hull side and the liner to the gunnel cap. Near the transom the gap between the liner and hull was about 7" (at the sole height). The foam fully supported the sole -- there was a 2" gap between the stringers and the sole; the sole was a part of the liner and was not attached anywhere else (as seen in the gap on this picture).





So by the old build, I said four bulkheads meaning inner stringer to inner stringer as they had been and then 4 more structures to go from inner stringer to outer and on to the hull sides. Perhaps they should simply be a continuation of the bulkheads, making them from hull side to hull side.

From the top of the stringer (bottom of sole) to the top of the hull side (bottom of the cap) is 22" starting near the transom and increases to 25" twelve feet from the stern. From the chine to the bottom of the sole will be roughly 7" near the transom and 6.5" twelve feet forward. The sides of the liner were about 1/4" thick (measuring what remains on the hull now) and the thickness of the gunnel cap (where rod holders mount) is about 7/8" (about 3/4" wood and at least 1/8" glass either side).

For now, my plan is to go across the bottom of the hull from inner stringer to chine, to hull side, and up hull side 6" first layer then up 4" more every additional layer of the 1708 and 1808 biax (4 total layers). So the first layer will be at or just below sole height but the other three layers will be above the sole height. Cleats would later be glassed onto the layers of biax and then the sole epoxied to the cleats (and bulkhead cleats, etc.) and then filleted and tabbed to the sides.
I will add more pictures later when I can get the camera cable -- I forgot to get it last night.
I appreciate your help.

Doug

[tech_support]

THANK YOU

For now, my plan is to go across the bottom of the hull from inner stringer to chine, to hull side, and up hull side 6" first layer then up 4" more every additional layer of the 1708 and 1808 biax (4 total layers). So the first layer will be at or just below sole height but the other three layers will be above the sole height. Cleats would later be glassed onto the layers of biax and then the sole epoxied to the cleats (and bulkhead cleats, etc.) and then filleted and tabbed to the sides.

Those are good overlaps

In the original hull configuration the area between the inner and outer stringers and outer stringers and hull sides were filled with foam. This foam also went up the sides between the hull side and the liner to the gunnel cap. Near the transom the gap between the liner and hull was about 7" (at the sole height).

OK, that tells me they were just relying on the buoyancy foam to stiffen up the sides (which it does, for a while)

The foam fully supported the sole -- there was a 2" gap between the stringers and the sole; the sole was a part of the liner and was not attached anywhere else (as seen in the gap on this picture).

That pretty normal on boats of this size and larger. I still prefer full height stringers to make the "egg crate" grid, but they are not needed if you use deck beams. You would be surprised how small stringers can be (in terms of height) and do their primary job (stiffen hull in longitude). For example if you look at a boat like a bertram 31', the stringers are only 6" tall or close, then they use deck beams and bulkheads to support decks/sole.

[doug42190]

Thanks,

So "deck beams" are they glassed under the sole to stiffen it or those additional structures I called frames -- are they deck beams? What do you call the cross members that make up the "egg crate" system (with the stringers)? Bulkheads side to side or just between inner stringers?

To use that schedule of biax up the sides will put the final layer about 6" or so below the cap bottom. I suppose I could then use some sort of longitudinal structure -- cardboard tubes cut in half and several layers of glass, then horizontally tabbed and glassed to the sides -- like 3" tubes cut in half -- perhaps 12" below the cap? Just trying to plan for all of this as I go. Does it look like I will need vertical supports as well if I did the tube thing?

These are some supports I made to stiffen and support the cap to the sides. I am sure I may need more later but this was a start.



That was my last question for the day -- I need to get a list together to order epoxy -- I used up everything I have on hand and I need more. This will be my first time using your epoxy -- looking forward to checking it out.

Thanks,
Doug

[doug42190]

I did some research and now understand the concept of deck beams -- my boat won't have any, correct?

[doug42190]

I have now laid 3.75 layers of glass going from the inner stringer, port side, to and then up the hull side, alternating up the side 6" then 4", 4", and 4". They are 1708, 1808, 1708, and 1808. I ran out of 1808 so I have to get more -- missed completing that side by 1 section of 50" X 57" more less.
I will try to get pictures up this evening. Next I will put in the outer stringer on the port side, fillet, and tab. Then I will feel like I am starting to get somewhere -- but then I have the whole starboard side to put in 4 layers, the stringer, etc.-- I am getting the hang of "slinging 'glass." I calculated that I would use just over 4 gallons of epoxy (thinking 60:40 resin to glass). I am getting ready to open the 5th one to finish this part of the project -- not counting the port stringer. All 4 layers combined were roughly 20 - 21 square yards -- so that seems about right math wise to me -- any comments would be appreciated.
Thanks,
Doug

[tech_support]

Sounds like your right on track with the ratios of glass/resin

[doug42190]

I layed a rather generous fillet on the outside of the inner stringer and then put a generous fillet where the side of the hull meets the chine. The stringer fillet I covered with 3 layers of 12 ounce tape, wet on wet. The chine/hull "joint" I only put 1 layer as I really was only trying to soften the transition from the side to the chine -- it was a very steep angle and would have been impossible to get the glass to stay in the "joint" as the layers piled on.



Next, I began to mark off and lay the glass in that area. In all, I have 4 layers of glass that go down the inner stringer, up to the chine, then up the hull side staggered -- 6", 10", 14", and 18".
Here is a picture with the marks showing with the first 2 layers installed.



Layer three was more of the same but on layer 4, I ran out of 1808 just over 4 feet from the transom. I got more glass and finished that portion up.
Here is a shot of the four layers that you can see pretty clearly.



Here is a pretty good picture showing the overlap of the last layer -- the glass was 50" wide but the run from the top of the stringer over the hull, chine, etc. and up the side 18" turned out to be 57". So I had to overlap the glass 2 or 3 inches (of the 50") which gave me 47"-48" X 57" strips from the forward end of the stringer back to the transom. The first 3 layers were put in with each layer in 1 piece -- what was I thinking?



I let that set up for a few days and then "spot welded" the outer stringer into place with thickened epoxy and wood flour.





This weekend I will finish the fillet on both sides and tape both sides of the outer stringer with 12 ounce tape -- three layers, wet on wet.
Then, time permitting, I will start the same process on the starboard side -- 4 layers (1708 and 1808), new outer stringer, etc.

Thanks for looking and I appreciate any feedback, comments or ideas.
Doug

[Cracker Larry]

Very nice work