Bob from Olympia, 28 GA build

[Brian.Dixon]

Well ...This is a 2-part question at least.

First, you get a bunch of difference forces piling up on the transom.  For example, every time the boat flexes (oil-canning and hogging), the transom corners try to flex as well.  Those corners are stress concentraters.  To fight that and to prevent breakage of the epoxy fillet and glass at those corners, you want to build strong fillets (see the construction manual on this) ...but you also want a stiff transom.  So even though your motor will be out on a hull extension, this boat flex will be occurring regardless.  I vote for a strong transom, your 'rear bulkhead' above, and would go 1" thick from the deck up.

The motor, especially on an extension, will throw it's weight and thrust around and try to impart racking (twisting) forces on the transom.  Part of that will also impact the transom (your 'rear bulkhead') ...I would go ahead and go with 1" thick down to the bottom panels.

The Proverbial Bottom Line: I vote for a 1" thick transom from sheer to fairbody...

For the minor weight increase compared to going lighter, I would encourage building a little stronger as spelled out above for boats like yours that have an extended hull (which I like better than an Armstrong type bracket for example).

Brian

[Rbob]

Sounds good on the 1" rear bulkhead.  Looks like I will make bulkhead to sit on  deck, just have to leave room to slip the main deck between stringers and rear bulkhead.

• laminate the riser's on the rear stringers
• add the deck on the extended transom, glassing inner surface first
• laminate 1/2" plywood for rear bulkhead, glassing inner surface first
• cut out and install rear bulkhead from stringers up to shelves
• big fillets with mini fibers added and biax and woven glass
• tape the transom exterior per glassing schedule

[Rbob]

Lots of planning and thinking for me, I cant visualize easy access to all seams with rear bulkhead and deck of extended transom in place which I need in place to tape exterior transom / side seam.  I need to router a slot in the motor mount beam to accept the rear deck, need to think more. 

[Brian.Dixon]

You can reach everything prior to the deck pieces going in, but there is no way to glass seams on the bottom of the deck, e.g. where the deck rests on stringers.  That's why you make sure that everything under the deck, and the perimeter of the decking itself, is waterproofed with plenty of epoxy (and glass as it seems fit) prior to laying the deck down ...there is only epoxy gluing it in place on the underside, and tape just on the top seams once the decks are in.

bd

[Rbob]

When taping the interior transom to the sides/hull the glass will start and stop at the stringers or lap onto the stringers?
Then when taping the stringers do I need to extend that glass onto the transom?

[Brian.Dixon]

When taping the interior transom to the sides/hull the glass will start and stop at the stringers or lap onto the stringers?
Then when taping the stringers do I need to extend that glass onto the transom?

The stringers-to-bottom panel glass does not wrap onto the transom - it's a heavy structure.

The glass tape that goes on the transom-to-bottom panel seam is easiest to install with nearly no overlap onto the stringers, but I like glassing the ends of the stringers to the transom (interior face) as well ...it's easiest to glass the stringers to the transom as a separate step.  Hope that clarifies things... sorry if the manual wasn't clear enough on this stuff.

Brian

[Rbob]

Thank you, the manual is probably clear enough its me that overthinks this stuff all the time. 

Bob

[Brian.Dixon]

Thank you, the manual is probably clear enough its me that overthinks this stuff all the time. 

Bob

Every boat builder spends a ton of time thinking through stuff... it's the nature of the beast ...and results in a better boat

bd

[Rbob]

I glassed the front chine's with 8" x 10oz cloth and 12" x 12oz biax. 

I may have messed up, doing a spreadsheet today and discovered that I purchased 0/90 biaxial 12", I used this on the forward chine seam, rear section has 2 rows of +/-45. 

[Brian.Dixon]

I glassed the front chine's with 8" x 10oz cloth and 12" x 12oz biax. 

I may have messed up, doing a spreadsheet today and discovered that I purchased 0/90 biaxial 12", I used this on the forward chine seam, rear section has 2 rows of +/-45.

No worries... there is plenty of glass on the boat, and with those beams and decks in place, those chines are well beyond strong enough.  Your 0/90 biax is stronger than standard woven since the layers of glass yarn lay flat, and the boat is fine with just standard woven.  Keep on truckin' ....go fishing sooner!

Brian

[Rbob]

That takes a load off of my mind! 

[Brian.Dixon]

That takes a load off of my mind!

You'll find that the boat is stiff and stout and then you won't doubt... haha, that rhymes!  Relax... be happy...

bd

[Rbob]

The extended transom does add time to the build for sure, I had to install risers on the stringers, loft and cut the rear bulkhead (2 pieces of 1/2") laminate and install from underneath the boat, while I was down there I installed the transom knees to the rear bulkhead that I installed. I put 2 " radius fillets on the rear bulkhead and 30oz of glass with glass mini-fibers as well.

I still have to put 3" fillets on the rear transom (vertical portion at least and I may end up doing this after the deck is on from underneath)and glass 30oz with mini fibers added, mount the deck on the extended portion (from underneath the boat) before I can finish taping the exterior transom seams and sides to the rear bulkhead and deck I added. And before the deck goes on I have to glass the underside of the deck since accessibility will be limited.

I am not complaining, just sayin...

On a side note I am having trouble using taptalk with this sight and reset password will not work.
 

[Brian.Dixon]

I wouldn't do all that underneath taping until the boat is upright, and I would build the outside seams now.  After turning, then go back and do the interior seams and add decking.  Am I missing something here?

bd

[Rbob]

I think so, the deck on the extended platform has to be taped to the sides. The deck will give limited access to the transom.  The pic below does not show the bottom panels installed, the rear bulkhead is yellow and the rear deck is green, I will have to reach the transom thru this access.  The second pic is crude, to show how sides will be taped to the rear deck.  Hope it makes sense.