Shearwater 17 Hybrid, Making Sure the Deck Forms are Properly Aligned before Gluing the Forms to the Hull


I am working on a Shearwater 17 Hybrid kit.  I have finished glassing the hull and now need to hot glue in the deck forms.  My forms in the middle, forms 6 to 11 in the instructions, aren't lining up well with the sheer clamps.  These forms sit low on the sheer clamps, so I will have to hold them up with a helper while I hot glue them in.  the forms at the bow and stern, 1-5 and 12 to 16, line up well with the sheer clamps.  How can I make sure the alignment of the middle forms is true to the plans?  Should I just eyeball this?  The instructions just say the spacing of the forms is nominally 12" but aerospace precision is not required.  They go on to say, get the forms reasonably close and the deck will go together fine.  I will have to lift the # 6 and 10.5 forms up a bit when I glue them to make sure the forms are higher than the bulkheads.  I have some photos, but don't know how to post them to this message board.

I tried searching the web, and saw that in the past templates for planing the sheer clamp were included with  kits, but no template came with my Shearwater 17 hybrid kit.  I have used these kit templates to plane sheer clamps when I built a Chesapeake kit years ago.  The current instructions eliminate the template, and use the forms as the angle of the bevel for planing the sheer clamps.

I saw a post from Tempest 170 dated 8/21/2021 with a response from Hspira, indicating it isn't uncommon for the panels to widen a little from the design.  Hspira suggested holding the panels together with fiberglass strapping tape before filleting, but that is too late for me.  The fillets are in and the hull panels are glassed.  

I am working on this project slowly, so it would make sense to keep the hull panels in the proper shape while I work on the deck.  My wife thought using fiberglass stapping tape might damage the fiberglassed hull when I try to remove the tape.  I have never used fiberglass strapping tape.  Could it cause damage to the hull if I apply it to the fiberglass hull panels to keep the panels locked in shape?  I plan to paint my hull rather than have a varnished finish, but I wouldn't want the fiberglass strapping tape separate the hull fiberglass from the okoume side panels.




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RE: Shearwater 17 Hybrid, Making Sure the Deck Forms are Properly Aligned before Gluing the Forms to the Hull

Hi Jim, 

it would be great to learn how to post pics, but while you are sorting that out, happy to try to help.  there are a couple questions in here so let me try to parse them out and take them one by one.

looks like the first question is about the placement of the hot-glued temporary forms that need to be attached to the hull and their positioning?   in reading your comments i would say the following:  the height of the forms relative to one another is more important than their spacing....which while it's supposed to be 12 inches....can have some variation.  the main reason for variation in spacing is becuase the hull expands a bit and the form, without coaxing the sides of the hull together, won't sit properly.  if this can be addressed by moving the form up or back an can do that, otherwise, i would keep them in their design position and get a helper to help you push the hull sides together while you are waiting for the hot glue to set.   if you can't find a helper, you can temporarily use blue tape to pull the sides together while you glue the form.

but as mentioned, more important than the spacing is the height.   this is important becuase if you get this messed up, you could end up with a wavy deck that has bulges.  you can, as you suggest 'eyeball' this but i would test my 'eyeball' by taking out one of the strips (make sure you choose a strip that is straight)a nd use it the check the alignment of the tops of the forms.   if you temporarily push a cedar strip onto the forms and you get a nice, smooth curve, you are all good.  if you see a wave, you need to move one or more forms to correct the problem.  sighting down the length of the strip is a good technique to see if you have a wave or other bend that needs to be addressed.

it appears your second question is about strapping tape and is it dangerous?  first, let me confirm where i use strapping tape.  i use it when i need to hold something in position, not have it move, and i am dealing with a lot of tension that would break or stretch other types of tape.    so if there is not a lot of pressure, i typically get the job done with blue tape....and the strapping tape comes into play only when there is a lot of muscle used to get something into position and then hold it there.

fwiw, i have never had strapping tape pull fibreglass off of wood or anything close to that.  the strapping tape (with glass filaments in it) is super strong in tension - not adhesion (which is the force that would pull the surface off).....where it is just like any other tape.   if you do use tape to hold things in place (blue tape, straping tape or other types) you want to use a high quality brand like 3m so that it will not leave a residue on your boat.  cheap imitations sold on amazon should be avoided because they will leave tape goo all over your work. i have had this problem and will never do it again.  i have never had that problem with 3m....but it costs a bit more.   

there seems to be another question about holding things in position?  this issue is more relevent to the deck then the hull of a hybrid.  this is becuase strip construction, if left alone for a long time, can really drift from its original shape.  so after you remove the staples, you do not want to leave it unattended or glassed only on one side for a long time.  just tape it down to the forms or throw a couple staples back in if you have to be away for a week or more.   

you mentioned that you already filleted the hull....and that's ok.   its when you try to line up the hull and deck for final assembly that you will see how hard you need to work to pull it all into alignment.  if you need a lot of muscle, then use the strapping tape to help you.  if blue tape will get the job done, that's fine too.

anyway, no problem taking it slow.  you should enjoy it.  i hope my response was helpful.


RE: Shearwater 17 Hybrid, Making Sure the Deck Forms are Properly Aligned before Gluing the Forms to the Hull

just one other tip i wanted to offer about using tape on a hull.  since the plan is to remove the tape, i always fold over one edge on itself of any tape i place on a i have a piece of the tape that is not sticking to the piece.  this provides a convenient 'handle' to pull the tape off the piece.  it can get very frustraing trying to remove tape if all the edges have been pushed down into the piece :)

when removing a piece of tape with the handle i described above.... i don't pull the tape up, but simply pull back along the piece back towards its other side.  this helps for a nice clean and easy removal.


RE: Shearwater 17 Hybrid, Making Sure the Deck Forms are Properly Aligned before Gluing the Forms to the Hull

   Thanks for your comments.  I will likely working on the forms over the weekend.

RE: Shearwater 17 Hybrid, Making Sure the Deck Forms are Properly Aligned before Gluing the Forms to the Hull

Hi Jim, 

some additional perspective on the step you are on.  i did have a helper when i built the  hybrid (built it with my nephew during covid - it was his first ever project).  we did spend a weekend getting the forms in.  we worked slow, tested everything out, and had to reset some pieces that were not properly positioned and reglue some pieces that did not seem to want to stick.

since the quality of the deck and boat depends so much on this, its worth taking your time.

here is a picture with the first strips we attached -- which were the ones down the middle and the sides.  the ones down the middle quickly give you a visual if the height of the forms are where they are supposed to be and if there is a 'wave' or 'bulge'. 

so you can see in this picture that the lines are smooth.  we did have a couple forms that we reglued becuase the initial check with a strip showed a they were not lined up right.   if you do have to move a form after you glued it, use an exacto to try to cut the glue as much as possible then use a mallet banging sideways as close to the hull as possible....else you can break the form.


RE: Shearwater 17 Hybrid, Making Sure the Deck Forms are Properly Aligned before Gluing the Forms to the Hull

Reinforced tape on the hull and/or deck............. I just put a strip built Petrel Play together. I used tape from our house stocks, which may have come Harbor Freight.  Good for packages.   That old adhesive is real persistant. It is taking a lot of denatured alochol  and scrubbing to remove it.    Use new 3m tape when joining the hull and deck. Don't leave it on very long.  During construction I used blue 3m with no problems. 


What H said about the deck and hull alignment moving when the two are seperate is true, like during interior glassing. It is typical with strip construction.  . Keep that time as short as you can. They have a tendancy to move.  Compress and expand with care to align. I'm having to fix a couple of cracks. 


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