How flat is flat enough

[Wally Teresch]

I recently picked up a new fiberglass sport 40 hull at a pretty good price. I was working on it and it was time to sand the thing and that's when I noticed that the bottom had major bulges in it. They went from front to rear as well as from side to side. This is not just a little body filler and sand job, this is a re-casting of the hull. The bulges start just forward of the turn fin and go all the way to the transom.

How flat does this ride plane need to be? In my mind this is the portion of the hull that sits on that cushion of air and if it isn't flat the boat will do all kinds of bazaar moves as it goes down the straightaway when air is 'spilling' out from under the hull.

Thanks

Wally

 

[SayMikey]

Question is can you get it flat by sitting it on a flat surface and adding weights? I had a new scale that was the same way,I drilled holes in the inner structure and squeezed in some West and milled glass mixture. Set it on a flat surface with all the weight I could get on the hull. When it dried it was flat again.....

 

[P THOMAS]

That is one of my 40 roundnose. That foam core caused the high spot. BUT dont worry it will be fine, the boat I race is not real flat either and it handles real well.

If you set the hull on a flat table it should set on the sponosn and the rear of the transom should be sitting flat on the table. That shape actually dumps air a bit better than perfectly flat.

Like you say to flatten it would mean cutting out the whole bottom in the rear.

I will have to use a thinner core for those boats.

Mikey you are so smart. Maybe you could get a hacksaw blade in there and cut a slot in that foam and reglue it with some weight on it.

 

[Wally Teresch]

I've contemplated that but have one concern, the Amine blush on the epoxy. If I do that the puddles of epoxy may let go unless I grind off the blush on the outer skin from the inside through the small holes. Is there any way of removing the blush without grinding?

As far as the outter going flat, there is one large spot where the outter hull is 'oil canning'.

I was thinking of taking some 1/32 ply and lamininating it with some light cloth between two pieces and putting it between some thick window glass so it comes out flat. Then after a few days of cure time take that and set the boat on it and epoxy it on. It will add weight and reduce the tunnel by about 3/32" but hopefully it comes out flat.

 

[SayMikey]

I had no issues with the glue letting go. I drilled 7/16 holes so I could get plenty of glue in the right areas. When I weighted it down some glue came back out the holes sealing it. Milled glass has plenty of bite to hold

 

[Dasboatman]

Hey Walthor,

You have input from the builder that it does not provide an issue with his own hull and indeed, may well help dump air. In the 4th pic you posted, the curve up to the transom will be a good thing - called "Recurve" by some.

I have seen Phil's own boat run, and it well might be one of the stronger Sport 40s of any style I've seen in a number of years. He gave my Buddy all he wanted and them some in Reserve in 2010. RB was breathin' hard after that heat - worked his arse off and couldn't drive around him.

I would guess cutting, and adding more material to the hull to flatten it would most likely do more harm than good - - adding weight with little other benefit to performance.

I say - rig and paint that puppy as designed. CHEERS !!! Bob

 

[moparbarn]

walthor, entirely off subject, but where did you get the straightedge/level/ruler with the handle? got a manufacturer's name? neat tool . sorry for the hijack, back to our regularly scheduled program.

 

[Rick Reisinger]

Leave it alone > it is not in contact with the water ...... Just get it together and make sure you can drive something fast -lol

= I am building one to Miss Timex / Phill's is a Bardall / OLD SCHOOL KOOL > Going to see if we can whip those late model pointy thing's...............

Rick Reisinger

 

[Wally Teresch]

walthor, entirely off subject, but where did you get the straightedge/level/ruler with the handle? got a manufacturer's name? neat tool . sorry for the hijack, back to our regularly scheduled program.

Whacha gonna do with it anyway, half of it is metric, including the levels? LOL

I can't see any markings on it but it is quite nice (not just because of the levels)

Sorry I can't help you out.

Wally

 

[moparbarn]

thanx for checking, wally. metric's not an issue been, dealing with it since i started working on air cooled vw's back in the 70's.