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jacquesmm wrote: ↑Fri Aug 20, 2021 6:41 pm
From the designer:
I was out of two for a couple days and could not reply earlier.
Please, do not get the lamination schedule from a friend or neighbor, get them from me, the designer.
There are several Phantoms built in foam sandwich and some hybrid. The very first one was around 1994, a PH18 that used Airex.
I calculated the specs for the PH22 years ago, was that not for you?
If not, I will check my files and we can discuss that next week. We just unloaded our suitcases, I'll check all that over the week-end.
We will also discuss the reverse chines.
Jac, have you had a chance to look for the lamination schedule for the PH22 foam core yet? Thanks.
I did not forget but put it on the back burner.
It's one thing to specify Divynicell H80 for a light boat like the FS18 but the bottom of a low deadrise 22 footer going 45 mph needs top of the line core and different laminating specs.
I am worried about your choice of a 250 HP. The slamming loads are a function of the square of the speed and that boat will be very fast with a 250. This is a flats boat hull, there will be more slamming than in a deeper vee like the CS23/25..
30 years ago, we did build an excellent foam cored PH18 that I tested for a few months going 50 mph but the bottom was plywood cored, only the bottom and the hull weight was 550 lbs. The idea was to avoid shear failure in the bottom.
I have specs for a number of foam cored planing boat bottoms up to 45' but those are built professionally.
There are two differences: the type of material (core and resin) and the "hinges". What I call the hinges are the chine and the keel. The very stiff side and bottom panels will want to flex along those lines and that is where we need to make a transition from core to single skin about 6"wide. If not, the core may fail in shear along those hinges.
You will need Corecell A in a high performance resin like the Silver Tip post cured or even Phase II.
The keel and chines must be made with a single skin transition. Those parts are difficult to build. When we plank the hull, all along the keel and chine, we replace the Corecell with a cheap throw away foam, When the outside skin is cured, boat flipped, we grind down the cheap foam, taper the good foam and build up a single skin along those "hinges".
All that is not necessary in most small boast for which I give foam core specs. Even a PH22 could be built with full cored chines and keel if you stayed below the max. 125 HP.
Another solution is to build the bottom panel in single skin fiberglass. That is easier but more costly. From the chine to the keel, you will plank with a sheet of heavy glass laminate: just like you would do with a plywood bottom. You could even use vinylester for that panel. After the boat is flipped, frame molds removed, you will build up the bottom to about 12 mm. It will cost more in material but it is a forgiving method, it's difficult to go wrong that way.
Consider the building method I describe above and the extra cost. If you still want it, I will write the specs. I may add a disclaimer.
ProfzX I did not realize you were looking to put a 250HP motor on your PH. Jacques recommends a 125HP for a reason as it will get it into the mid 40's. Doing a fiber glass version will make it lighter and increase its high speed. I calculated the PH with a 250 0n it and a 250 will give it a top speed of around 70mph. Jacques will have to heavily reinforce the bottom for speeds like that.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978
“You will need Corecell A in a high performance resin like the Silver Tip post cured or even Phase II.
The keel and chines must be made with a single skin transition. Those parts are difficult to build. When we plank the hull, all along the keel and chine, we replace the Corecell with a cheap throw away foam, When the outside skin is cured, boat flipped, we grind down the cheap foam, taper the good foam and build up a single skin along those” "hinges"
Then I should be able to build the entire hull by this method correct? I could use some “cheap” insulation foam board in place of the divinycell then grind it away and use my divinycell for stringers and bulkheads. No?
Then I should be able to build the entire hull by this method correct? I could use some “cheap” insulation foam board in place of the divinycell then grind it away and use my divinycell for stringers and bulkheads. No?
Yes but I still prefer the 2nd method: build the bottom as a single skin panel.
Then I should be able to build the entire hull by this method correct? I could use some “cheap” insulation foam board in place of the divinycell then grind it away and use my divinycell for stringers and bulkheads. No?
Yes but I still prefer the 2nd method: build the bottom as a single skin panel.
Can you please send me the lamination schedule for both methods?
This is honestly becoming a little frustrating. Prior to me even purchasing these plans I inquired on wether or not this build could be done as a foam core with the HP I was wanting. I was directed by Jeff to post this question on the forum and that you would respond. Which you did and at that time your response was it was doable but that you’d have to give a separate lamination schedule for both the hull bottom and also the transom. I followed thru with my $4k worth of foam purchase and now am being told that the only way it will be possible is if I use a different more expensive foam or not even use foam all together. Please forgive me for feeling a little hoodwinked here.
Please see the max. HP listed for the PH22. That is where the problem is.
I don't remember stating that a foam core version for 250 HP was doable with plain Divynicell.
I can give specs for a foam cored hull rated for max. 125 HP, bottom cored but not for a 250 HP version.
The lamination schedule for the bottom and the sides are always different.
Thank you Jac. If you can please send me your recommended lamination schedule of both ways you mentioned so that I may equip the hull with a 250hp I’d appreciate it. Thanks.
ProfrsX Why do you keep insisting on a 250HP motor, are you build this for bass tournaments? Jacques just said he would give you the laminating schedule for a 125HP but not for a 250HP motor. Like I posted above a 250HP will give you speeds around 70mph, speeds that Jacques does not design his boats for as he does not want to take the liability for. If you want to add extra glass to the outer and inner hull and beef up the transom, that is your choice and your responsibility and your liability.
P
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978
You need more than a schedule, you need some drawings showing the layup. I will scan pages from my books and foam data sheets.
In the mean time, please check this small PDF file, it explains what is involved;
I have an old printed version but that book is the bible of composite building. Skip over the details but see what I list below.
The construction methods that I mentioned start at page 180.
On page 269, look at figure 5-13, on the right side, it shows the transition to single skin.
Page 289 shows the overlaps that I specify.
I have more reference material with core manufacturers specifications for typical boats and will send you specs after this week-end.
Email to jacques@boatbuildercentral.com and I will reply with specs.
