67 flatback project - father and son

[Tampa Bay Mike]

Yeah like they said, if you round over the inside corners it should sit in a little better.  I would start there and then see how it looks. I wouldn't want to grind out too much of the new glass since it is essentially holding it all in. Those three extra layers won't do you any good if you grind them out right at the corners. Also, not sure if you are using poly or epoxy but it may be worth the extra $$ for some epoxy to fill the gaps that are left since it will have more structural strength than the poly.

[mshugg]

I see now that that is the step from the lip formed by your old transom. I should have read your description better.   I’d be inclined to layer in 2 or 3 more layers of glass to bring the hollow up to level with the inside skin.  It would be better than any other filler.

When you tab new glass into old, it’s best to grind a taper into the old glass. Twelve to one is the generally accepted ration, so of your skin was 1/4” thick, you would taper back 12/4” or 3”.  Then you layer in your glass so that it creates a level transition.  There are two schools of thought, bigger pieces first, or smaller first.  I now subscribe to the bigger pieces first, because you won’t be grinding through your full size pieces of glass to get a level surface.  In something structural, like a transom, you would then add full layers that lap I to the hull sides over your level skin.

Your transom will be fine.  In fact by building out the hollow, you would be creating an inside out version of what I described.

[RickK]

Take string and stretch it across the outside of the transom - is it a flat line or a bowed line?

[ncrowe]

I see now that that is the step from the lip formed by your old transom. I should have read your description better.   I’d be inclined to layer in 2 or 3 more layers of glass to bring the hollow up to level with the inside skin.  It would be better than any other filler.

When you tab new glass into old, it’s best to grind a taper into the old glass. Twelve to one is the generally accepted ration, so of your skin was 1/4” thick, you would taper back 12/4” or 3”.  Then you layer in your glass so that it creates a level transition.  There are two schools of thought, bigger pieces first, or smaller first.  I now subscribe to the bigger pieces first, because you won’t be grinding through your full size pieces of glass to get a level surface.  In something structural, like a transom, you would then add full layers that lap I to the hull sides over your level skin.

Your transom will be fine.  In fact by building out the hollow, you would be creating an inside out version of what I described.

Went a different route - but I think it'll all work out the same

Yeah like they said, if you round over the inside corners it should sit in a little better.  I would start there and then see how it looks. I wouldn't want to grind out too much of the new glass since it is essentially holding it all in. Those three extra layers won't do you any good if you grind them out right at the corners. Also, not sure if you are using poly or epoxy but it may be worth the extra $$ for some epoxy to fill the gaps that are left since it will have more structural strength than the poly.

Thanks - I did grind a little and it's much better now

Take string and stretch it across the outside of the transom - is it a flat line or a bowed line?

Rick - the outer skin is nice and flat

 :1rij:Problem solved! I ground some material from the coosa and now the entire board sits flat. just trimmed 1/8 - 1/4" where needed around the perimeter (2" around the edge at the most). I figured this would be the best way to do it with the least mount of effect on any structure



I might shave a touch more here - maybe another 1/8"


Also made some large clamps today - used some non marring wood clamps from HB and then extended them with some select pieces of 1x3 - I made 7 of them for about $60

[Tampa Bay Mike]

Looking nice. I know I wanted to do it all in one day but with something as important as this it's good to take your time and get it right.

[RickK]

Looks better.  Make sure you round off the rear edges so you don't have an abrupt edge different from the round fillet you'll add next before troweling the thickened resin to bed the coosa in.

[ncrowe]

Question: can you make fillet material out of poly? I have been purchasing a premise fillet material by the gallon, but I’m sure there’s a way to make it. I was told it’s more complicated than just mixing in some solids (cabosil or whatever)

Does anyone have a recipe to make the peanut butter from poly?

Thanks!

[mshugg]

Yes, you can make Polly based filler.  The big difference is with Polly you add catalyst  after adding filler; with epoxy you add filler last. 

Fillers can be talc, wood flour, milled fiber, chopped fiber, micro balloons, glass spheres, and silica.  The balloons and spheres are better  for fairing.  For fillets, I like 50% milled fiber, 25% wood flour and 25% cabosil.  You’re going for a peanut nutty consistency.

 The exact ratio isn’t important.  Too much silica can be brittle.  Too much wood flour can absorb so much resin it makes for a dry fillet.  The chopped fibers are stronger, but harder to get smooth.  I think most premixed fillers (bondo) use talc instead of woodflour.

[Tampa Bay Mike]

There are a lot of different recipes for it but it always seemed to me that buying the premixed stuff was more cost effective and consistent. You can get a gallon of putty from FGCI for $57. By the time you buy everything to make your own you'll be close to that easy plus you'll have the hassle of mixing it vs opening a can and going. Just a thought.

[RickK]

I used Duraglass to fair some of the bottom of hull but always mixed fillet material myself. Usually you don't have much fairing to do on fillets. The key to getting good smooth fillets is to use the right tool. Mix your "putty" with one of these, makes the putty nice and smooth - https://www.homedepot.com/p/HDX-1-gal-Helix-Paint-Mixer-HM1-HDX/206509381
To spread/form the fillets you can use wooden spoons of different sizes or make your own to fit the space needed. Big paint stir sticks (like for 5 gal buckets, free from HD and Lowes, are a good start too. Then use a grinder to round it off to fit the corner and also round off the edges. You can cut the big stir sticks in half and make 2 from each. Over the course of your rebuild you'll end up with a few sizes.

[mshugg]

Another thing that’s helpful is getting consistent amounts of material into the corners.  Grout bags  allow you to pipe an even amount.  These are what I used: https://www.amazon.com/Kraft-Tool-WL009-Disposable-50-Pack/dp/B00SYE2M46/ref=pd_sbs_469_t_0/135-5665126-1857211?_encoding=UTF8&pd_rd_i=B00SYE2M46&pd_rd_r=94769ef4-36dc-40d8-933e-b15f205f88ba&pd_rd_w=b6dbV&pd_rd_wg=GYfSv&pf_rd_p=5cfcfe89-300f-47d2-b1ad-a4e27203a02a&pf_rd_r=HR33JZ17DCC9CP8MGT3G&psc=1&refRID=HR33JZ17DCC9CP8MGT3G

Some people use pastry bags, or a zip top bag with the corner cut off, but grout bags are tougher and easier to work with.

[RickK]

Yup, agree with mshugg, choose the bag you'll use (I used a gal size freezer bag with corner cut off - whatever works for you).
A trick is lay a pencil flat on the core that is sitting in dry and mark a line along the hull sides and bottom.  This should be about a 1/4" inside the boat from the core. You should be planning to trowel thickened resin (1/4" notch) onto the inside of the transom to bed the core.  The line you drew with the pencil shows where you don't want to trowel past, so you can trowel a couple inches of resin on the hullsides and hull bottom to help fill the corners and edges.  If you get lucky you may not need a fillet if you trowel it on thick enough in the corners.

[RickK]

Any progress?

[ncrowe]

Have to put the boat up for sale - my youngest has some health issues that need to be resolved (heart and respiratory) - So I'll pass this boat along to another member

[Tampa Bay Mike]

I saw the ad for it the other day. I actually thought about it but my wife would kill me if I brought another project home. I have always liked the look of those old flatbacks.

Sorry to see it go, good luck with the sale.