HM19 10hp cruising speed?
Re: HM19 10hp cruising speed?
It duplicated on me, sory. Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978
- OrangeQuest
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Re: HM19 10hp cruising speed?
Yes, I understand that one hull is designed to be a planning hull and one is not. But does that mean a planning hull at less than planning speed, displacement speed, will not perform as well as a designed for displacement speed hull?
In other words, a 10hp motor will push a planning hull at the same speed as a displacement hull for a give weight if the DWL are the same in both length and width of both hulls? And are the two hull designs at displacement speeds the same DWL for the same weight?
In other words, a 10hp motor will push a planning hull at the same speed as a displacement hull for a give weight if the DWL are the same in both length and width of both hulls? And are the two hull designs at displacement speeds the same DWL for the same weight?
"that it isn't just an ordinary sort of boat. Sometimes it's a Boat, and sometimes it's more of an Accident. It all depends." "Depends on what?" "On whether I'm on the top of it or underneath it."
A. A. Milne
A. A. Milne
Re: HM19 10hp cruising speed?
Man, I really messed up my orignal question
I should've just asked: What is the expected top displacement speed be for the HM19.
Bogie
I should've just asked: What is the expected top displacement speed be for the HM19.
Bogie
Re: HM19 10hp cruising speed?
My calculator shows up to displacement speed range speed of 6-14mph since this is a planing hull. But the displacement speed calculated was 6.07mph for the boat and motor combination. So, if you compare the HM to the HMD there is an added 3" in draft and some other differences in shape between the two designs. It would be hard for the HMD to reach much over 7mph even with a lite load. Your correct in your statement "if everything were equal" but in real life a displacement boat would never be the same to float the same DWL.
Tom
Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978
- Evan_Gatehouse
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Re: HM19 10hp cruising speed?
Well both HM and HMD. Both are at displacement speeds here.
Here is a boat test of a Lud Impact 1775, an aluminum open fishing boat. As light as a HM19 I would guess. Moderate V hull
http://www.boatmaginternational.com/636 ... roke-f115/
Notice the fuel consumption at 5.2 knots. 1.1 gph is about 10 HP in a 4 stroke gasoline engine.
To get it to 7.4 knots you nearly double the fuel consumption so you're around 18 HP.
Here is a boat test of a Lud Impact 1775, an aluminum open fishing boat. As light as a HM19 I would guess. Moderate V hull
http://www.boatmaginternational.com/636 ... roke-f115/
Notice the fuel consumption at 5.2 knots. 1.1 gph is about 10 HP in a 4 stroke gasoline engine.
To get it to 7.4 knots you nearly double the fuel consumption so you're around 18 HP.
designer: FB11/GV10,11,13/ HMD18/
SK17,MM21/MT24
SK17,MM21/MT24
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Re: HM19 10hp cruising speed?
OrangeQuest wrote: ↑Sat Feb 11, 2023 12:39 am Yes, I understand that one hull is designed to be a planning hull and one is not. But does that mean a planning hull at less than planning speed, displacement speed, will not perform as well as a designed for displacement speed hull?
In other words, a 10hp motor will push a planning hull at the same speed as a displacement hull for a give weight if the DWL are the same in both length and width of both hulls? And are the two hull designs at displacement speeds the same DWL for the same weight?
Obviously, at displacement speeds the hull designed for such will be better. It will be more efficient, track better, ride more smoothly. It will not be faster unless you are operating with very limited hp. 10hp is 10hp, but the displacement hull might go the same speed with 6hp.
- Evan_Gatehouse
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Re: HM19 10hp cruising speed?
If you want to always go slow pick the HMD. If you think you might plane one day and go fast, pick the HM. You can still go slow with the HM with a small motor.
designer: FB11/GV10,11,13/ HMD18/
SK17,MM21/MT24
SK17,MM21/MT24
Re: HM19 10hp cruising speed?
Bogieman just put your 10HP on it now. When you are able to upgrade to a larger motor do it. I will be glad to work out what your speeds will be depending on the HP you choose. Right now, Evan and I are sort of in agreement but with some terminology mixing us up. Just remember you have a planing hull which will be more efficient once you get into planing speeds, at displacement speeds the boat is not efficient though the 10HP motor may be. I would try to save up and get the 30-50 HP as soon as possible.
Tom
Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978
Re: HM19 10hp cruising speed?
Thanks all!
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