1999 Polar 1780 Flats Boat Rebuild

Questions about boat repairs with our resins and fiberglass: hull patches, transoms and stringers, foam, rot etc.
arcticbreeze
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1999 Polar 1780 Flats Boat Rebuild

Post by arcticbreeze »

I have edited the title because I am going to use this thread to document my progress

Pictures are below the text

I am finally ready to order some materials and I am hoping to get little help on some quantities. I have a 17 ft (the beam is 6 ft) polar that I have had for a few years. All of the sudden I was having some problems getting on plane with my 40hp (max hp on the tag is 75hp) Yamaha. I originally assumed the motor was losing power so I had everything gone over and tuned and even experiment with some different prop pitches to no avail. Finally someone suggested the problem may be water logged foam so I cut an inspection hole and dug out some of it and sure enough, water logged so I assume it was not closed cell. So I removed the console, cut out the sole and dug out all the foam. Well bad went to worse. The cheap ply was water logged and had large gaps between the bottom of the stringer and hull, the glass (poly) was not wetted out in more than 50 percent of the length and so on and so on. So I decided a complete rebuild was in order. Another thing I was amazed about is the rear left corner of the rear casting deck was assumable installed to low and the top then filled with resin (about 1” thick) to bring up the level of the deck to the gunnels height.

When I took the debris to the dump it weighed almost 900 lbs. The boat is perfect for me as far as size and hull shape. Draft was very shallow and before the problems it zips along at 25 mph with decent fuel consumption. I am hoping with the weight savings once put back together with good wood and epoxy performance should be great. Sorry about the long rant, now on to the details.

The boat is 17 ft long and from this picture you can see that the plywood (2 x ¾ ply) is only partially covering the transom. That would be the first change I would like to make. The rear corners are rounded so there will be little fitting to do but that should be no problem. I plan on cutting 3 layers of ½ in at full profile then stepping each piece in to conform to the rounded corner.

There are only 2 stringers with some frames in the mid section between the 2 stringers. The original had nothing from the stringer to the hull except the sole however I think I would like to add some. The stringers are 13 ft 2 in long and 9 ¼ in tall at the tallest point comprised of ¾ in ply. I was planning to replace those with a double layer of 3/8 epoxy glued together then adding the frames that were on the original construction of which there were 3 between the 2 stringers then add the same number of frames from the stringer to the hull sides. The original sole looked like it was 5/8 ply with a thick maybe 1/4 in layer of chopped glass on top. I was thinking that with the extra frames I could use 3/8 in with a layer of 6 oz on top. The original had transom knees on top of the sole about 9 in tall, I am thinking of bringing those all the way down to the hull and all the way up to the rolled gunnels and using them to support the rear casting deck which would be level with the gunnels. That would make the transom knees approx 48” long to match the rear deck. The old front deck was 66” from front to back the width of the boat 6 ft. it was made of ¾ ply and glassed around the gunnels and only supported at the rear of the deck with ¾ ply. There was not any flex to the deck at all which surprises me given that span. If I support the deck in the middle with another frame can I use 3/8 instead? I could them have a compartment in the front for an anchor locker and storage or fuel storage behind that. I do have one 3 gallon kit of marine epoxy originally purchased from here for a different project but this is more important. I am hard on my boats and only wish to have a no frills work type boat. I would like to cover all the deck surfaces just for some abrasion protection. Can I get away with maybe 4 oz fabric? All the seams will be 12 biax tape and then I assume I will need some 12 oz Biax cloth for the transom. Does my plan seem sound? I would like to place an order with you this week if possible and I can work out the quantities.

PS I forgot to add that the stringers are 25" center to center apart and are parallel. From the stringer to the chine is 14" in the rear and tapers slightly to approx 13" forward.

As far what I think I need:

3 more gallons of epoxy (for a total of 6)
5 lbs wood flour
??? yds 12 oz biax tape
??? yds 12 oz biax cloth
??? yds 4 oz fabric
2 sets of plunger pumps

I have access to some marine fir really cheap but it is all 3/8 and 1/2. So I would like to try to stick to those sizes.
Thanks in advance

Marc

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Hopefully I have given all the need info. If not please let me know and I will get it.
Last edited by arcticbreeze on Fri Feb 26, 2010 7:51 pm, edited 4 times in total.

arcticbreeze
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Re: Finally time to order with a little help

Post by arcticbreeze »

Oh, I almost forgot. Should I cover the inside of the hull with clothe first before the stringers are installed or can I just epoxy coat it? it is currently approx 1/4 thick (including gel coat). The transom skin is slightly thicker but not much (maybe another 1/32).

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Re: Finally time to order with a little help

Post by tech_support »

Thanks for the post, it has all the info I need :D , including pictures :!: :D
I plan on cutting 3 layers of ½ in at full profile then stepping each piece in to conform to the rounded corner.
That is good
The stringers are 13 ft 2 in long and 9 ¼ in tall at the tallest point comprised of ¾ in ply. I was planning to replace those with a double layer of 3/8 epoxy glued together then adding the frames that were on the original construction of which there were 3 between the 2 stringers then add the same number of frames from the stringer to the hull sides.
That is how I would make the stringers also. No problem adding the floor frames, it will add stiffness and make for more gluing area for the sole. 3/8" is OK for 25" span. Make sure you give a good gluing surface on top of the stringers and frames (use cleats). 1/2" would work also (either one will be ligght than what was there). Cover sole and decks with at least 6 oz woven, 4 is pretty light for that kind of boat (fishing). The old thick layer of chopped matt and polyester resin probably weighed 5 times more than an epoxy/6oz covering.
The old front deck was 66” from front to back the width of the boat 6 ft. it was made of ¾ ply and glassed around the gunnels and only supported at the rear of the deck with ¾ ply. There was not any flex to the deck at all which surprises me given that span. If I support the deck in the middle with another frame can I use 3/8 instead?
If you break the spans up with frames you can reduce the deck thickness to 1/2" or even 3/8". Two frames would be plenty to divide 66".

Im not fully understanding what you propose for the transom knees, but its always a good idea to bring them up as high as practical.

Your list is good, I would just replace the 4 with 6 oz, and your going to need enough biax wide cloth (17 or 12) to make an iside skin to equal the original thickness, probably 3/16" to 1/4". Your going to need at least 2 rolls of 12 oz biax tape for all the tabbing of stringers/frames/transom core/sole. I would add 1 bag of silica to the list as well. For a job this big, I would forget the pumps, pour into graduated cups.

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Re: Finally time to order with a little help

Post by tech_support »

arcticbreeze wrote:Oh, I almost forgot. Should I cover the inside of the hull with clothe first before the stringers are installed or can I just epoxy coat it? it is currently approx 1/4 thick (including gel coat). The transom skin is slightly thicker but not much (maybe another 1/32).
no reason as long as you did not grind thickness away, or unless there is damage to repair. You do need to grind past the gelcoat in places where you will be tabbing in new parts. We want the epoxy to be bonding to glass, not gelcoat. If you epoxy something to gelcoat, the weak link is then the old glecoat's bond to the hull

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Re: Finally time to order with a little help

Post by arcticbreeze »

Thanks for the detailed reply :D . I am ordering today.
shine wrote:Im not fully understanding what you propose for the transom knees, but its always a good idea to bring them up as high as practical.
What I meant was that instead of them sitting on top of the sole up to the rear casting deck as in the original construction, I would bring them down to meet the hull.

I think from reading what seems like hundreds of threads on this wonderful board I have a good handle on this but once I get started I am sure I will be confused again :lol: .

Thanks again for a wonderful resource.

Marc
Last edited by arcticbreeze on Wed Feb 24, 2010 2:47 pm, edited 1 time in total.

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Re: Finally time to order with a little help

Post by arcticbreeze »

Ok, I just placed my order. I figure this should get me started. I figure I will order the 6oz cloth and anything else I need once I get a little ways in to the rebuild. I will mix larger batches by weight but I think the pumps will be convenient for smaller batches. I took your advice and ordered the silica but I am not sure of its appropriate use? Please forgive my ignorance :doh: .

Marc

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Re: Finally time to order with a little help

Post by arcticbreeze »

:D :D :D :D

Wow, I am impressed. I just want to say that the service you guys at BBC provide is 2nd to none. I placed my order yesterday, my stuff was here today (I am in FL). There was a small error, I sent an email earlier today, was responded to very promptly (Thanks Joel) and there is already a tracking number emailed. I will say that you have definitely earned my patronage. With this kind of service I would order here even if I could find it cheaper locally (which I can't). Thanks again guys.

Marc

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Re: Finally time to order with a little help

Post by FitzFisher »

i AGREE THAT THESE GUYS ARE ON TOP OF THEIR GAME. This is a very valuable site for all of us that feel the itch of boatbuilding (YukYuk). Looks like you will have a great boat for cruising the flats off the 'Cotee when you get done. And you won't have to wait till they dredge the channel with that draft! :D The original construction doesn't impress me much, but that's production I guess. I think you are on the right track with your buildup, and will have a bulletproof skiff! Jaques and Shine, Correct me if I am wrong, but if he puts a couple extra frames in there, it should really help with torsional twist that is common in the low sided skiffs like that, no? Party on, Wayne!
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Re: Finally time to order with a little help

Post by tech_support »

FitzFisher wrote:Correct me if I am wrong, but if he puts a couple extra frames in there, it should really help with torsional twist that is common in the low sided skiffs like that, no? Party on, Wayne!
We know it will not hurt :D How much it will help depends on a lot of other things (the gunnels help a lot too), but building an "egg crate" internal structure is going to make for a more stiff boat than the same one with just stringers.

Since you mention it up...... If there was noticeable twisting before, then you need to make those frames EXTRA strong = double or triple tabbing all around. If the boats flexing an moving around, and now you are going to "pin" the stringers together, those frames will be under a lot of stress.

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Re: 1999 Polar 1780 Flats Boat Rebuild

Post by arcticbreeze »

The hull had zero flex in it before even in 4' swells running hard ahead of a storm. (I was running from a water spout)I want the additional support in order to use thinner wood on the sole. I think the rolled gunnels help too. With the stringers 25" apart in the center and three frames which would make a max span of approx 25" x 38", will 3/8" ply with 6 oz cloth be good. I think adding one more set of frames would be lighter than an increase to 1/2" on the sole. That would make the max span about 25" x 31". Or I could use stiffeners or do you think the original span with 3/8 ply and 6oz cloth is good. I also notice a thread about the fs18 where it was suggested to laminate the underside of the sole and the top of the 1/4" ply instead of going to 3/8" if foam was not used.

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