AGM Rules 2.1-2.3 discussion (Composite hulls)

[Chad]

With a new builder of glass boats coming soon (Congrats to M&S and to Geoff/juswannagofast on the deal), I think it would be in our Class' best interest, in the RDO's interest, and would raise the value of the i550 brand and the worth of our individual boats if we were seen to be unified behind that effort by allowing composite hulls in our Class.

(In general, I think we should post rules ideas first, discuss those ideas, then propose rule language base on the discussion. There's been some discussion of this rule amongst some of us already, so I'll just post the rules language we have so far. Feel free to pick at it though, if you see something that doesn't work)

Italic = words removed
bold = words added

2.1 Hull bottom and side panels shall include commercially available plywood at least 1/4" nominal thickness (5.2mm minimum actual thickness). Balsa plywood or other similar lightweight non-structural wood shall not be permitted for this requirement.

Hull panels shall be constructed so that the panel weight is substantially similar throughout. 1/4" nominal plywood shall always be construed to meet this rule, or a non-plywood composite with a uniform base laminate schedule throughout. Any hull laminate may have specific reinforcements for anticipated loads, but shall not be generally lighter in the ends, for instance. (see Rule 4.2)

2.2 Hull side and bottom panels shape shall be cut to the specifications of the i550 plan set as provided by the copyright holder and assembled to fit within the bounds provided with this section (plywood). The shape of a non-plywood hull shall be similarly controlled.

2.3 Chines may be rounded in nature, however all hull panels shall make contact along the chine (plywood). The amount of chine radius for non-plywood hulls, and the allowable deviation from designed shapes that this rule allows by choosing other than inner-corner to inner-corner contact, shall be the same for any hull construction.

2.4 Deck and cabin may be constructed of any material. (Deleted)

Comments:
2.1- Ply is still allowed, and any 1/4" nominal ply has no rules issues. A composite builder needs to assure us (I own a bunch of hole saws, and cut my own test samples!) that they are using a uniform panel weight, generally.
2.2- This rule depends on plywood construction, so I want to make its intent applicable to composite hulls for hull shape control.
2.3- Same reasoning as 2.2.
Should 2.4 be deleted? I'm thinking no now, since that would seem to imply that the deck and cabin are now subject to the uniform hull panel weight idea?

[jray]

Sorry I may have jumped the gun on the rule change for hull materials. At the time I was posting I didn't realise you had posted this one up. I can retract the proposal of more time is needed.

[Chad]

Well, for formality's sake, I (or somebody) needs to second yours, or you (or somebody) needs to second mine! Which one do you like better? Mine didn't misspell "construe" like yours did!

[jray]

I will second yours. Consider it done

Yours looks better anyway.

[ryderp]

How much lighter could they make the ends of the boat? 1/4" plywood is fairly light on a sq. ft. basis and there has to be some amount of thickness in any construction to avoid a lot of deflection of the hull (especially with flat surfaces). As far as the chines are concerned why not just define a maximum radius and be done with the reference to 1/4" plywood? Personally, I'm OK with any rule that standardizes and keeps the same: 1)the hull shape, 2) the total weight of the boat, and 3) the keel weight. Of course there still have to be the rules about corrector weights, rules against shiftable ballast (at least the non-human kind), etc.

Phil

[jray]

In reference to total boat weight, keel and bulb weight, these are set in the rules. There is no rule governing shiftable ballast. Maybe something to bring up as a discussion/proposal.

[Chad]

I did some panel weight studies a couple years ago and figured I could make a stiffer glass/foam composite hull panel that was about 75% of the weight of a ply/glass panel. If a lighter panel like that is used, there would need to be a lot of extra structure put into the middle of the boat, to avoid the punitive correctors our class uses. If a builder undershoots the hull weight by too much more than about 60#, our rules will hurt that boat a bunch.

Building in plywood automatically spreads the weight around pretty evenly. With a composite build, there's room in the weight budget to concentrate the extra weight low near the CG and make a boat that handles a lot differently. This is gyradius optimization, and it's a big deal in areas with chop or waves.

The RRS already deals with shifting ballast, no need to double reference in Class rules.

[jray]

As many times as I've read everything lately I missed that. Sorry!

[micah202]

I did some panel weight studies a couple years ago and figured I could make a stiffer glass/foam composite hull panel that was about 75% of the weight of a ply/glass panel. If a lighter panel like that is used, there would need to be a lot of extra structure put into the middle of the boat, to avoid the punitive correctors our class uses. If a builder undershoots the hull weight by too much more than about 60#, our rules will hurt that boat a bunch.

Building in plywood automatically spreads the weight around pretty evenly. With a composite build, there's room in the weight budget to concentrate the extra weight low near the CG and make a boat that handles a lot differently. This is gyradius optimization, and it's a big deal in areas with chop or waves.

The RRS already deals with shifting ballast, no need to double reference in Class rules.

..

....it'd be something for the builder to consider 'cheaping' out on materials,,use matt,foam rather than techy cloths...
......this would achieve the performance/rule goals,,and keep co$ts down...I can't imagine the builder would want to obsolete the fleet they're building for!

[M&S]

WS-V is quite aware that a boat built with intentionally light ends would violate the trust of all the existing and future i550 builders. We shall produce hull and deck material with weight proportionally matching the wood weight plus resin and fiber content per square area. TR

[Chad]

I didn't doubt that, T.
But "trust, but verify" keeps partners from doubting each other, eh?

Still, I salivate at what could be done with a liiittle bit of tech and no weight rules to work to. I'm picturing an i550 with just one ring frame near the keel and a midline stringer, and totally open inside otherwise. Nice stiff panels that don't need gobs of frames and stringers and corners to tape. I wonder what the cost trade off is between simplicity of building versus stitched cloth/mat cost?

[M&S]

in my dreams the boat is filled with Helium, framed for rig loads only and has foils and an automatic wheat soda dispenser that sensess my need. oh and an acceleration couch with joystick controls.

I am with ya and have gone beyond the edge. T